Next Article in Journal
Oliviculture and Viticulture Crop Byproducts Use for Peat Partial Substitution for Carnation Production
Next Article in Special Issue
Brassinosteroids: Relevant Evidence Related to Mitigation of Abiotic and Biotic Stresses in Plants
Previous Article in Journal
Impact of Winter Cover Crops on Total and Microbial Carbon and Nitrogen in Black Soil
Previous Article in Special Issue
Phenylalanine Ammonia-Lyase-Mediated Differential Response of Tomato (Solanum lycopersicum L.) Cultivars with Different Stress Tolerance to Treatment with Low-Molecular-Weight Chitosan
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Agronomy
Volume 14
Issue 3
10.3390/agronomy14030604
agronomy-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

The Effects of Brassinosteroids on Nitrogen Utilization in Rice

by
Wei Yang
1,†,
Guo-Feng Wan
1,†,
Jia-Qi Zhou
2,
Gen-Cai Song
3,
Jing Zhao
2,
Feng-Lin Huang
3,* and
Shuan Meng
1,*
1
College of Agronomy, Hunan Agricultural University, Changsha 410128, China
2
College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha 410128, China
3
Hunan Rice Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Agronomy 2024, 14(3), 604; https://doi.org/10.3390/agronomy14030604
Submission received: 27 February 2024 / Revised: 13 March 2024 / Accepted: 15 March 2024 / Published: 18 March 2024
(This article belongs to the Special Issue Regulatory Mechanism of Growth Regulators on Crop Growth and Development)
Browse Figures
Versions Notes

Abstract

:
Nitrogen and brassinosteroids (BRs) play a vital role in modulating the growth, development, and yield of rice. However, the influences of BRs on nitrogen assimilation and metabolism in rice are not fully understood. In this study, we analyzed the impact of BRs on nitrogen utilization in rice using the indica variety ‘Zhongjiazao 17’ and the japonica variety ‘Nipponbare’ in hydroponic conditions. The results showed that BR treatment could efficiently elevate nitrate and ammonium nitrogen accumulation in both shoots and roots. Furthermore, some genes involved in the uptake of nitrate and ammonium in roots were stimulated by BRs, though we noted subtle variances between the two rice cultivars. Moreover, BRs augmented the activity of nitrate reductase (NR) and glutamine synthetase (GS) in roots, along with NR in shoots. Interestingly, BRs also spiked the total free amino acid content in both the shoots and roots. Gene expression analysis uncovered a robust induction by BRs of NR genes and GS-related genes in the roots of both ‘Nipponbare’ and ‘Zhongjiazao 17’. Collectively, our data suggest that BRs significantly enhance the accumulation of both nitrate and ammonium in rice and trigger a series of reactions related to nitrogen utilization.

1. Introduction

Nitrogen (N) is essential for crop growth and development, playing a crucial role in plant metabolism. It is particularly vital as it often limits crop productivity. Insufficient nitrogen can hinder plant growth, disrupt nitrogen and carbon metabolism, lower photosynthesis, and reduce the production of amino acids and proteins [1,2]. To address this, nitrogen fertilizers are commonly used to enhance crop yields. In fact, global fertilizer usage has significantly increased over the past 60 years, rising from 32 million tonnes in 1961 to 202 million tonnes in 2020, a six-fold increase [3]. However, the excessive use of nitrogen fertilizers has started to impact agricultural systems and ecosystems [3,4], leading to pollution. Balancing the need for increased productivity with environmental concerns necessitates the improvement of nitrogen use efficiency (NUE). Soil contains various forms of nitrogen, but plants primarily rely on inorganic nitrogen in the form of nitrate and ammonium as their nitrogen source [5]. The processes involved in nitrogen utilization by plants encompass uptake, translocation, assimilation, and remobilization [6]. Nitrogen utilization efficiency is regulated by proteins responsible for nitrate and ammonium transport, as well as enzymes involved in assimilation [1].
In plants, the genes responsible for the transport of nitrate can be classified into four main groups: NRT1, NRT2, CLC, and SLAC/SLAH [7]. Among these members, NRT1.1 is a versatile transporter protein that can exhibit both high and low affinity for NO3− depending on the phosphorylation and dephosphorylation of amino acid residue T101, respectively [8]. In rice, the uptake of nitrate from the external environment involves the participation of four high-affinity nitrate transporter (NRT) proteins, OsNRT2.1, OsNRT2.2, OsNRT2.3, and OsNRT2.4, and one low-affinity nitrate transporter, OsNRT1.1A [9]. Ammonium, like nitrate, is an important nitrogen source for plant growth. It is taken up by plants through ammonium transporters (AMTs) [10]. Rice, for example, possesses 12 predicted AMT genes. Among them, AMT1.1, AMT1.2, and AMT1.3 belong to high-affinity ammonium transporter proteins, and the remaining members all encode low-affinity transporters [11].
After rice absorbs nitrogen from the environment, the majority of it is utilized and processed, with only a portion reserved for storage purposes. Nitrogen assimilation is a fundamental physiological process crucial for plant growth and development. Inorganic nitrogen must undergo conversion into organic nitrogen compounds, such as glutamine and glutamate, before plants can utilize it effectively [12]. Nitrate reductase (NR) serves as the initial enzyme in the assimilation of nitrate [12]. Additionally, glutamine synthetase (GS) is another key enzyme involved in nitrogen metabolism, responsible for assimilating ammonium in higher plants [12].
Brassinosteroids (BRs), a class of polyhydroxylated plant steroid hormones, play pivotal roles in governing crucial traits for crop improvement [13]. Regulating leaf angle represents a specific functional role of BRs in diverse crop species [14]. BRs are also involved in modulating responses to diverse stressors encompassing salt, drought, cold, and heat, as well as environmental stimuli such as light, water, and nutrient availability [15]. Brassinosteroid (BR) recognition in rice primarily entails the interaction between the leucine-rich repeat receptor-like kinase (LRR-RLK) OsBRI1 and coreceptor SERK-family proteins (OsSERKs), situated on the cellular membrane. The ensuing signal cascade is subsequently transduced downstream through a diverse array of protein families, including BSK kinases (OsBSKs), GSK3/SHAGGY-like kinases (OsGSKs), PPKL phosphatases (OsPPKLs), and BZR-family transcription factors (OsBZRs), involving intricate molecular processes such as phosphorylation and dephosphorylation [15,16,17,18,19]. Prevalent morphological traits exhibited by BR-deficient mutants across diverse species include their dwarf stature, compact architectural phenotype, and diminished size of various organs [15,20]. Moreover, some studies have indicated that applying BR during the rice booting stage can effectively maintain the content of nitrogen, phosphorus, and potassium in rice, delay chlorophyll degradation, and alleviate the effects of low-temperature stress [21]. Exogenous BR treatment has been found to alleviate growth inhibition caused by salt treatment in apple seedlings and increase the activity of nitrogen-assimilating enzymes in plants, promoting the transport of nitrate nitrogen from roots to leaves [22]. However, the exact effects of BRs on the nitrogen utilization process in rice are still not fully understood. In this study, we conducted a comprehensive investigation of the effects of BRs on nitrogen utilization in rice.

2. Materials and Methods

2.1. Rice Seedling Culture

The research investigation was conducted in Changsha, Hunan Province, China, in 2023. Two rice varieties, Zhongjiazao 17 (ZJZ17, indica variety) and Nipponbare (Nip, japonica variety), were used in this study. ZJZ17, an exemplary conventional indica rice cultivar, was identified as possessing superior agronomic characteristics, including high productivity and exceptional grain quality attributes, thereby solidifying its designation as one of the extensively cultivated varieties in China. By contrast, Nip, a japonica rice variety, has garnered substantial attention as an essential model organism for rice research owing to its well-established reference genome information. The seeds were soaked in tap water for 2–3 days until fully saturated, then spread out on germination plates. They were placed in a 30 °C dark incubator for 1–2 days, which allowed for early germination before carefully selecting uniformly germinated seeds to be grown hydroponically as described [23]. Seedlings were cultured under simulated natural light conditions in an artificial climate chamber (14 h/day at 30 °C and 10 h/night at 26 °C with 30,000 Lx of light intensity) until reaching the two-leaf-one-heart stage, and then they were treated with or without 2 µM BR for another 2 days.

2.2. Extraction of RNA and Quantitative Real-Time PCR Analysis

RNA was extracted from the leaves and roots of rice seedlings using the TransZol Up Plus RNA Kit (TransGen Biotech Co., Ltd., Beijing, China) and reverse transcription was performed with the cDNA Synthesis Kit (Yeasen Biotechnology Co., Ltd., Shanghai, China). qRT-PCR was carried out utilizing the Hieff qPCR SYBR Green Master Mix (High Rox Plus) kit (Yeasen Biotechnology Co., Ltd., Shanghai, China). The rice OsACTIN1 gene served as a reference for relative gene expression analysis. The primers utilized for qRT-PCR are listed in Table S1.

2.3. Determination of Nitrate Content

Nitrate concentration was determined according to Cataldo et al. [24] with minor adjustments. An amount of 0.08 g of the finely milled liquid nitrogen-treated fresh sample was placed in a 2 mL centrifuge tube, and 800 µL of 0.1 M HCl (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) was added. It was vortexed vigorously to mix and placed in an ice bath at 100 rpm for 2 h. Afterward, it was centrifuged at 4 °C and 12,000× g for 15 min. The supernatant was collected, centrifuged again for 1–2 min, and the supernatant was collected. An amount of 10 µL of the supernatant was mixed with 40 µL of a 5% salicylic acid (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China)–sulfuric acid (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) solution, incubated for 20 min, then 950 µL of 2 M NaOH (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) was added, vortexed, briefly centrifuged, and absorbance was measured at 410 nm. The standard curve is created using a KNO3 (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) solution.

2.4. Determination of Ammonium Content

We adopted the Schneidereit et al. [25] method with minor modifications. In the extraction of ammonium using 800 µL of 0.2 M HCl, the extraction process is the same as that for nitrate extraction. Then, 40 µL of supernatant, 20 µL of phenol reagent (a phenol and sodium nitroprusside mixture), 104.6 µL of ultra-pure water, 33.4 µL of 15% sodium hypochlorite solution, and finally 2 µL of NaOH solution were mixed. Following thorough mixing, it was incubated at 37 °C for 60 min before the absorbance was measured at 610 nm. The standard curve is constructed using an (NH4)2SO4 (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) solution.

2.5. Enzyme Activity Analysis

GS and NR activities in rice plants were assessed using commercially available assay kits from SolarBio, Beijing (GS: BC0910, NR: BC0080). For GS activity, 0.1 g fresh tissue was homogenized with 1 mL of extraction solution in an ice bath. It was centrifuged at 4 °C and 8000× g for 10 min, and then 175 µL of the supernatant was combine with the provided GS reagent. It rested for 10 min, was centrifuged at 5000× g for another 10 min, the supernatant was collected, and the absorbance was read at 540 nm. The GS activity is calculated as GS (U/g FW) = 19 × ΔA/FW, where ΔA is the difference in absorbance between the assay and the control tubes. For NR activity, 0.1 g fresh tissue was homogenized in 1 mL of extraction solution and treated as for GS. Initial absorbance was measured at 340 nm (A1), it was incubated in a water bath for 30 min, and measured again at 340 nm (A2). The NR activity is calculated as NR (U/g FW) = 5.359 × ΔA/FW, where ΔA is the difference between the assay and blank absorbance changes after incubation.

2.6. Determination of Total Free Amino Acids

Total free amino acids were extracted and quantified according to Rosen [26] and Jung et al. [27] with minor adjustments. A homogeneous sample weighing about 0.07 g, obtained by milling in liquid nitrogen, was transferred to a 2 mL centrifuge tube. Then, 800 μL 80% ethanol was added. Then, the samples were bathed in 80 °C water for 30 min, after which centrifugation was performed at 4 °C at 12,000× g for 15 min to collect 400 μL of the supernatant. This supernatant was then evaporated to dryness using a vacuum rotary evaporator and redissolved in 400 μL 0.02 M HCl. For analysis, 150 μL of this extract was added to a glass tube, along with 1850 μL of a 0.2 M pH 5.4 acetate buffer, followed by the addition of 3 mL of a fresh ninhydrin solution (prepared from 0.6 g ninhydrin in a mix of 15 mL n-propanol, 30 mL n-butanol, 60 mL ethylene glycol, and 9 mL of the same acetate buffer). To this, 0.1 mL of a 3% ascorbic acid solution was added. The mixture was subjected to boiling water for 15 min and then cooled in cold water. The resulting solution was diluted to 20 mL using 50% ethanol, and its absorbance was measured at 580 nm. A standard curve was constructed using leucine.

2.7. Data Analysis

Data were processed and analyzed using Microsoft Excel 2016 (Microsoft Corporation, Redmond, WA, USA) and Graphpad Prism 8 (GraphPad Software, La Jolla, CA, USA). Values in the graphs indicate means ± SD, n = 14 in Figure 1, and n = 3 in other figures. Differences between groups were evaluated using the T test function built into these software platforms, with one asterisk indicating a significant difference at the p < 0.05 level and two asterisks denoting a p < 0.01 level of significance.

3. Results

3.1. Rice Seedling Growth in Response to BRs

In this study, we discovered that treating rice seedlings with BRs at the two-leaf-one-center stage for 2 d increased the leaf angle significantly when compared to the control group (Figure 1a,b). This indicates that our processing is effective and can be used for subsequent nitrogen utilization analysis. Additionally, after BR treatment, the plant heights of ZJZ17 and Nip were significantly higher than control group (Figure 1c,d), with no difference observed in the root (Figure 1e,f).
Agronomy 14 00604 g001
Figure 1. Rice phenotypes under Brassinosteroids (BR) treatment. (a,b) Phenotypes of Zhongjiazao17 (ZJZ17) (a) and Nipponbare (Nip) (b) rice seedlings at the two-leaf-one-heart stage that continued to be incubated normally for 2 d with or without 2 μM BR. (c,d) Statistical data of plant height for ZJZ17 (c) and Nip (d) of the corresponding materials in (a). (e,f) Root length of ZJZ17 plant (e) and Nip plant (f) statistics for the corresponding materials in (a). Values in the graphs are means ± SD (n = 14, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Figure 1. Rice phenotypes under Brassinosteroids (BR) treatment. (a,b) Phenotypes of Zhongjiazao17 (ZJZ17) (a) and Nipponbare (Nip) (b) rice seedlings at the two-leaf-one-heart stage that continued to be incubated normally for 2 d with or without 2 μM BR. (c,d) Statistical data of plant height for ZJZ17 (c) and Nip (d) of the corresponding materials in (a). (e,f) Root length of ZJZ17 plant (e) and Nip plant (f) statistics for the corresponding materials in (a). Values in the graphs are means ± SD (n = 14, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Agronomy 14 00604 g001

3.2. The Effects of BRs on Nitrate and Ammonium Accumulation in Rice

The primary utilization forms of nitrogen are ammonium and nitrate. We measured the contents of these two nitrogen species in the shoots and roots of ZJZ17 and Nip after BR treatment and observed a significant increase in nitrate and ammonium accumulation compared to the control group (Figure 2). This indicates that BRs might promote the accumulation of nitrate and ammonium in rice plants.

3.3. The Effects of BRs on the Expression of Rice Nitrogen Uptake-Related Genes

To better understand how BRs regulate nitrogen uptake and transport, we examined the expression of key genes responsible for these processes in rice roots. We focused on nitrate transport protein genes OsNRT2.1, OsNRT2.2, OsNRT2.4, OsNRT1.1A, and OsNRT1.1B, as they mediate nitrate transport. RT-qPCR analysis revealed differential gene expression responses to BR treatment in ZJZ17 rice roots. Specifically, an upregulation trend was noted for OsNRT1.1A (Figure 3a), OsNRT1.1B (Figure 3b), and OsNRT2.4 (Figure 3d), whereas OsNRT2.1 and OsNRT2.2’s expression levels were suppressed (Figure 3c). In Nip roots, BR treatment led to a notable induction of OsNRT1.1A, OsNRT1.1B, and OsNRT2.1/NRT2.2 (Figure 3e–g), but OsNRT2.4 expression remained relatively unchanged (Figure 3h).
For genes related to ammonium uptake and transport, BR treatment significantly induced the upregulation of OsAMT1.1 (Figure 4a) and OsAMT2.1 (Figure 4d) in ZJZ17, with OsAMT1.2 (Figure 4b) and OsAMT1.3 (Figure 4c) showing no significant difference. In Nip, the expression levels of the entire suite of genes, OsAMT1.1 (Figure 4e), OsAMT1.2 (Figure 4f), OsAMT1.3 (Figure 4g), and OsAMT2.1 (Figure 4h), were upregulated in response to BRs. These differentially expressed genes might be involved in the rice plants’ nitrogen utilization response to BR treatment.

3.4. Influence of BRs on Nitrogen Assimilating Enzyme Activities in Rice

We then assessed the impact of BRs on NR and GS enzyme activities in the shoots and roots of Nip and ZJZ17 rice variants. The results depicted in Figure 5 illustrate that after two days of BR treatment, there was a significant increase in the activities of shoots’ NR (Figure 5a,c) as well as roots’ NR (Figure 5b,d) and GS (Figure 5f,h). However, the application of BR significantly decreased the activities of GS in shoots (Figure 5e,g), which indicates the inhibition of GS activities by BRs.
Next, we analyzed the expression levels of genes encoding NR and GS in response to BRs. After BR treatment, the expression levels of OsNIA1, OsNIA2, and OsNIA3 were suppressed in the shoots of ZJZ17 (Figure 6a). Conversely, the expression of OsNIA3 showed a slight upregulation in the shoots of Nip (Figure 6b). Meanwhile, in the roots of both ZJZ17 and Nip, the expression levels of OsNIA1, OsNIA2, and OsNIA3 were significantly stimulated and upregulated (Figure 6c,d).
Glutamine synthetase in plants is categorized into cytoplasmic (GS1) and plastidic (GS2) types based on their localization [28]. In the shoots of ZJZ17, OsGS1.3 and OsGS2 exhibit decreased expression levels (Figure 7a). Conversely, in the Nip variety, the expression of OsGS2 is inhibited, while the expression levels of other GS genes remain unaffected by the BR treatment (Figure 7b). BR treatment leads to an upregulation of expression levels for all examined GS genes in the roots of both ZJZ17 (Figure 7c) and Nip (Figure 7d). These results highlight the complex regulatory effects of BRs on glutamine synthetase gene expression in different plant tissues and varieties.
NR and GS mediate the conversion of inorganic nitrogen to organic nitrogen, given that the accumulation of organic nitrogen within rice is primarily in the form of amino acids [28]; we analyzed the total free amino acid content after BR treatment for 2 d. The results revealed a significant elevation of amino acid levels in both the shoots and roots of rice (Figure 8). The data suggested that BR treatment elevated the accumulation of amino acid-N within the rice plants.

4. Discussion

Phytohormones are micro-efficient organic substances essential for the regulation of plant growth and development, and some hormones were proved to play a significant role in plants’ nitrogen utilization. For example, Methyl jasmonate (MeJA) influences the uptake of ammonium and nitrate in rice, potentially through OsAMT2.2, OsNRT1.2, and OsAMT1.1, which are believed to mediate the transport of these nutrients in rice roots after jasmonate (JA) stress [29]. Gibberellic acid (GA) can increase root length, volume, and surface area in cucumber, particularly under suboptimal root zone temperatures, thereby enhancing the roots’ capacity to absorb nitrogen and consequently improving nitrogen utilization [30].
The research presented indicated that exogenous BRs could influence nitrogen utilization in rice, leading to increased nitrate and ammonium accumulation in both shoot and root tissues (Figure 2). Rice has 12 ammonium transporter proteins within three subfamilies: OsAMT1, OsAMT2, and OsAMT3 [31]. The overexpression of OsAMT1.1 and OsAMT1.3 has been linked to improved nitrogen use efficiency at low-to-moderate ammonium concentrations, promoting growth in both shoot and root parts of rice and contributing to higher yields [32,33]. Root RT-PCR results indicated that BR treatment upregulates the expression of certain genes such as OsNRT2.4, OsAMT1.1, and OsAMT2.1 in ZJZ17, which may enhance the uptake of nitrogen in roots. Notably, previous research showed that the expression of OsAMT1.2 was upregulated by RELATED TO ABI3/VP1-LIKE 1 (RAVL1) at the appropriate concentration of BRs, thereby promoting ammonium absorption in rice roots [34]. Conversely, in Nip, a more robust response was observed with the upregulation of genes such as OsNRT1.1A, OsNRT1.1B, and OsAMT1.3 following BR treatment. The variation in expression levels of rice genes implicated in nitrogen utilization could stem from distinct response mechanisms exhibited by each gene towards nitrogen. Comparable patterns were noted following jasmonic acid (JA) treatment in rice and gibberellic acid (GA) treatment in cucumber, resulting in diverse expression levels of NRT-related genes [29,30]. This differential gene expression suggests that BRs may act on specific genes and exhibit varying effects depending on the nitrogen use efficiency of different rice varieties.
Nitrate is the principal form of nitrogen in most terrestrial plants, serving both as a nutrient and signaling molecule crucial for metabolism, growth, development, and environmental adaptation [35]. After uptake, plants convert nitrate into nitrite by NR, then to ammonium by nitrite reductase, and subsequently, ammonium is transformed into various amino acids through enzymatic catalysis. NR plays a crucial role in regulating and limiting the rate of nitrogen metabolism in plants.
Our study revealed that BR treatment significantly increased NR activity in both the shoot and roots of rice plants (Figure 5), accompanied by a marked upregulation in the expression of pivotal genes OsNIA1, OsNIA2, and OsNIA3 responsible for controlling NR activity in the roots (Figure 6). This observation suggests that BRs have the potential to modulate NR activity at the transcriptional level specifically in roots. However, the expression of OsNIAs showed only minor changes or remained unaffected by BR treatment in the shoots of both ZJZ17 and Nip varieties (Figure 6). Given the indispensable role of NR in plants, its activity regulation involves diverse pathways encompassing expression and protein levels. For instance, nitrogen deprivation in tomatoes resulted in decreased NR protein levels and activity without notable alterations in gene expression [36]. Recent research has demonstrated that the divergent nitrate assimilation and nitrogen utilization efficiency between indica and japonica rice are attributed to allelic disparities leading to the production of distinct structural forms of the OsNR2 protein in each subspecies [5]. This discrepancy contributes to the higher nitrate reductase activity observed in indica rice [5]. Furthermore, NR activity is also subject to regulation through post-translational phosphorylation modifications, where the dephosphorylation of NR enhances its activity and promotes the absorption and assimilation of nitrates [37,38]. These factors likely underlie the discrepancies observed in genetic expression and enzymatic activity outcomes in our study, underscoring the intricate nature of NR function regulation; however, further investigation is needed to elucidate the specific mechanisms involved.
During the vegetative growth stage of rice, the majority of the nitrogen taken up by the roots is assimilated and stored in the leaves in various forms including inorganic nitrogen, amino acids, and proteins [39]. Our research findings indicate that post-BR treatment, there is an accumulation of nitrate and ammonium in rice plants, along with an increase in the total free amino acid content. Studies have demonstrated that BR treatment can stimulate protein synthesis [40] and modulate plant growth and phenotype in nutrient-deficient conditions [41]. This includes enhancing root foraging response, influencing plant height, and improving nutrient uptake efficiency [41]. The combined analysis of our data suggests that BR treatment may enhance the absorption of external nitrogen by plants, thereby increasing the available nitrogen source and promoting the accumulation of different nitrogen forms within the plant, subsequently fostering plant growth. In high-nitrogen conditions, rice plants exhibit heightened nitrogen uptake from the external environment, accompanied by the increased activity of NR, resulting in nitrogen accumulation within the plant tissues [42]. It is crucial to note that NR activity is induced by nitrate and could be enhanced by increasing nitrate. Further investigations have revealed that melatonin treatment under low-nitrogen conditions can elevate NR activity in both the shoot and root of wheat seedlings, along with a significant increase in nitrate content [43].
Additionally, NR catalyzes the conversion of nitrite to nitric oxide (NO) [44,45,46]. Under BR treatment, there is an enhancement in the plant’s capacity to produce NO [47], while the presence of a truncated hemoglobin (THB) within the plant system aids in NO scavenging [48]. The expression of THB 1 is regulated by NO, NR, and nitrogen [49,50], facilitating the conversion of NO to nitrate [51]. Our study has shown an upregulation in nitrate reductase activity following BR treatment, albeit with a limited magnitude of increase, coupled with observed nitrate accumulation, suggesting a potential involvement of NO induced by BR in this process. The elevated NO levels by BR treatment may lead to nitrate accumulation through THB1 action.

5. Conclusions

Promoting nitrogen uptake and enhancing its utilization in plants are critical for reducing nitrogen fertilizer application and improving fertilizer efficiency in agriculture. This study highlights how BRs influence rice plants in the accumulation of ammonium and nitrate, as well as orchestrating a broad regulation over inorganic nitrogen metabolism and organic nitrogen accumulation like amino acids, through enzyme activity and gene expression levels. The specific pathways through which BRs exert these effects warrant further investigation and analysis.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/agronomy14030604/s1, Table S1: List of primer sequences used for qRT-PCR analysis in this study.

Author Contributions

Conceptualization, S.M. and F.-L.H.; methodology, W.Y. and G.-F.W.; formal analysis, W.Y. and G.-F.W.; investigation, W.Y., G.-F.W. and J.-Q.Z.; writing—original draft preparation, W.Y. and G.-F.W.; writing—review and editing, W.Y., G.-C.S., J.Z., F.-L.H. and S.M.; supervision, S.M.; funding acquisition, S.M., J.Z. and G.-F.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Hunan Provincial Natural Science Foundation of China: 2022JJ30284 and 2022JJ30304; Scientific Research Fund of Hunan Provincial Education Department: 23A0184; Graduate Research and Innovation Projects of Hunan Agricultural University: 2022XC036.

Data Availability Statement

Data are contained within the article and supplementary materials.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Dong, N.-Q.; Lin, H.-X. Higher yield with less nitrogen fertilizer. Nat. Plants 2020, 6, 1078–1079. [Google Scholar] [CrossRef] [PubMed]
  2. Liu, D.; Li, M.; Liu, Y.; Shi, L. Integration of the metabolome and transcriptome reveals the resistance mechanism to low nitrogen in wild soybean seedling roots. Environ. Exp. Bot. 2020, 175, 104043. [Google Scholar]
  3. Chai, Y.; Pannell, D.J.; Pardey, P.G. Nudging farmers to reduce water pollution from nitrogen fertilizer. Food Policy 2023, 120, 102525. [Google Scholar]
  4. Jain, A.K. Greenhouse gas emissions from nitrogen fertilizers. Nat. Food 2023, 4, 139–140. [Google Scholar] [PubMed]
  5. Gao, Z.; Wang, Y.; Chen, G.; Zhang, A.; Yang, S.; Shang, L.; Wang, D.; Ruan, B.; Liu, C.; Jiang, H.; et al. The indica nitrate reductase gene OsNR2 allele enhances rice yield potential and nitrogen use efficiency. Nat. Commun. 2019, 10, 5207. [Google Scholar]
  6. Marmagne, A.; Masclaux-Daubresse, C.; Chardon, F. Modulation of plant nitrogen remobilization and postflowering nitrogen uptake under environmental stresses. J. Plant Physiol. 2022, 277, 153781. [Google Scholar] [PubMed]
  7. Li, Z.; Na Wu, X.; Jacquot, A.; Chaput, V.; Adamo, M.; Neuhäuser, B.; Straub, T.; Lejay, L.; Schulze, W.X. Phosphoregulation in the N-terminus of NRT2.1 affects nitrate uptake by controlling the interaction of NRT2.1 with NAR2.1 and kinase HPCAL1 in Arabidopsis. J. Exp. Bot. 2023, erad490. [Google Scholar] [CrossRef]
  8. Sun, J.; Zheng, N. Molecular Mechanism Underlying the Plant NRT1.1 Dual-Affinity Nitrate Transporter. Front. Physiol. 2015, 6, 386. [Google Scholar] [PubMed]
  9. Hou, M.; Yu, M.; Li, Z.; Ai, Z.; Chen, J. Molecular Regulatory Networks for Improving Nitrogen Use Efficiency in Rice. Int. J. Mol. Sci. 2021, 22, 9040. [Google Scholar] [PubMed]
  10. Yang, S.; Yuan, D.; Zhang, Y.; Sun, Q.; Xuan, Y.H. BZR1 Regulates Brassinosteroid-Mediated Activation of AMT1;2 in Rice. Front. Plant Sci. 2021, 12, 665883. [Google Scholar] [CrossRef] [PubMed]
  11. Hao, D.; Yang, S.; Huang, Y.; Su, Y. Identification of structural elements involved in fine-tuning of the transport activity of the rice ammonium transporter OsAMT1;3. Plant Physiol. Biochem. 2016, 108, 99–108. [Google Scholar] [CrossRef]
  12. Konishi, N.; Ishiyama, K.; Beier, M.P.; Inoue, E.; Kanno, K.; Yamaya, T.; Takahashi, H.; Kojima, S. Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots. J. Exp. Bot. 2016, 68, 613–625. [Google Scholar] [CrossRef]
  13. Tong, H.; Chu, C. Functional Specificities of Brassinosteroid and Potential Utilization for Crop Improvement. Trends Plant Sci. 2018, 23, 1016–1028. [Google Scholar]
  14. Luo, X.; Zheng, J.; Huang, R.; Huang, Y.; Wang, H.; Jiang, L.; Fang, X. Phytohormones signaling and crosstalk regulating leaf angle in rice. Plant Cell Rep. 2016, 35, 2423–2433. [Google Scholar]
  15. Yang, Y.; Chu, C.; Qian, Q.; Tong, H. Leveraging brassinosteroids towards the next Green Revolution. Trends Plant Sci. 2024, 29, 86–98. [Google Scholar] [PubMed]
  16. Gao, X.; Zhang, J.-Q.; Zhang, X.; Zhou, J.; Jiang, Z.; Huang, P.; Tang, Z.; Bao, Y.; Cheng, J.; Tang, H.; et al. Rice qGL3/OsPPKL1 Functions with the GSK3/SHAGGY-Like Kinase OsGSK3 to Modulate Brassinosteroid Signaling. Plant Cell 2019, 31, 1077–1093. [Google Scholar] [CrossRef] [PubMed]
  17. Ren, H.; Willige, B.C.; Jaillais, Y.; Geng, S.; Park, M.Y.; Gray, W.M.; Chory, J. BRASSINOSTEROID-SIGNALING KINASE 3, a plasma membrane-associated scaffold protein involved in early brassinosteroid signaling. PLoS Genet. 2019, 15, e1007904. [Google Scholar]
  18. Tian, P.; Liu, J.; Yan, B.; Zhou, C.; Wang, H.; Shen, R. BRASSINOSTEROID-SIGNALING KINASE1-1, a positive regulator of brassinosteroid signalling, modulates plant architecture and grain size in rice. J. Exp. Bot. 2022, 74, 283–295. [Google Scholar]
  19. Yin, W.; Li, L.; Yu, Z.; Zhang, F.; Liu, D.; Wu, H.; Niu, M.; Meng, W.; Zhang, X.; Dong, N.; et al. The divergence of brassinosteroid sensitivity between rice subspecies involves natural variation conferring altered internal auto-binding of OsBSK2. J. Integr. Plant Biol. 2022, 64, 1614–1630. [Google Scholar] [CrossRef]
  20. Dai, X.; Zhang, Y.; Xu, X.; Ran, M.; Zhang, J.; Deng, K.; Ji, G.; Xiao, L.; Zhou, X. Transcriptome and functional analysis revealed the intervention of brassinosteroid in regulation of cold induced early flowering in tobacco. Front. Plant Sci. 2023, 14, 1136884. [Google Scholar] [CrossRef]
  21. Wang, S.-q.; Zhao, H.-h.; Zhao, L.-m.; Gu, C.-m.; Na, Y.-g.; Xie, B.; Cheng, S.-h.; Pan, G.-j. Application of brassinolide alleviates cold stress at the booting stage of rice. J. Integr. Agric. 2020, 19, 975–987. [Google Scholar]
  22. Yu, B.; Wang, L.; Guan, Q.; Xue, X.; Gao, W.; Nie, P. Exogenous 24-epibrassinolide promoted growth and nitrogen absorption and assimilation efficiency of apple seedlings under salt stress. Front. Plant Sci. 2023, 14, 1178085. [Google Scholar]
  23. Lin, J.-H.; Xu, Z.-J.; Peng, J.-S.; Zhao, J.; Zhang, G.-B.; Xie, J.; Yi, Z.-X.; Zhang, J.-H.; Gong, J.-M.; Ye, N.-H.; et al. OsProT1 and OsProT3 Function to Mediate Proline- and γ-aminobutyric acid-specific Transport in Yeast and are Differentially Expressed in Rice (Oryza sativa L.). Rice 2019, 12, 79. [Google Scholar]
  24. Cataldo, D.A.; Haroon, M.; Schrader, L.E.; Youngs, V.L. Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid. Commun. Soil Sci. Plant Anal. 1975, 6, 71–80. [Google Scholar] [CrossRef]
  25. Schneidereit, J.; Häusler, R.E.; Fiene, G.; Kaiser, W.M.; Weber, A.P.M. Antisense repression reveals a crucial role of the plastidic 2-oxoglutarate/malate translocator DiT1 at the interface between carbon and nitrogen metabolism. Plant J. 2006, 45, 206–224. [Google Scholar] [CrossRef] [PubMed]
  26. Rosen, H. A modified ninhydrin colorimetric analysis for amino acids. Arch. Biochem. Biophys. 1957, 67, 10–15. [Google Scholar] [CrossRef] [PubMed]
  27. Jung, B.; Flörchinger, M.; Kunz, H.-H.; Traub, M.; Wartenberg, R.; Jeblick, W.; Neuhaus, H.E.; Möhlmann, T. Uridine-ribohydrolase is a key regulator in the uridine degradation pathway of Arabidopsis. Plant Cell 2009, 21, 876–891. [Google Scholar] [CrossRef]
  28. Guo, N.; Zhang, S.; Gu, M.; Xu, G. Function, transport, and regulation of amino acids: What is missing in rice? Crop J. 2021, 9, 530–542. [Google Scholar]
  29. Wu, X.; Ding, C.; Baerson, S.R.; Lian, F.; Lin, X.; Zhang, L.; Wu, C.; Hwang, S.-Y.; Zeng, R.; Song, Y. The roles of jasmonate signalling in nitrogen uptake and allocation in rice (Oryza sativa L.). Plant Cell Environ. 2019, 42, 659–672. [Google Scholar] [CrossRef]
  30. Bai, L.; Deng, H.; Zhang, X.; Yu, X.; Li, Y. Gibberellin Is Involved in Inhibition of Cucumber Growth and Nitrogen Uptake at Suboptimal Root-Zone Temperatures. PLoS ONE 2016, 11, e0156188. [Google Scholar]
  31. Yan, Y.; Zhang, Z.; Sun, H.; Liu, X.; Xie, J.; Qiu, Y.; Chai, T.; Chu, C.; Hu, B. Nitrate confers rice adaptation to high ammonium by suppressing its uptake but promoting its assimilation. Mol. Plant 2023, 16, 1871–1874. [Google Scholar] [CrossRef]
  32. Bao, A.; Liang, Z.; Zhao, Z.; Cai, H. Overexpressing of OsAMT1-3, a High Affinity Ammonium Transporter Gene, Modifies Rice Growth and Carbon-Nitrogen Metabolic Status. Int. J. Mol. Sci. 2015, 16, 9037–9063. [Google Scholar] [CrossRef]
  33. Ferreira, L.M.; de Souza, V.M.; Tavares, O.C.H.; Zonta, E.; Santa-Catarina, C.; de Souza, S.R.; Fernandes, M.S.; Santos, L.A. OsAMT1.3 expression alters rice ammonium uptake kinetics and root morphology. Plant Biotechnol. Rep. 2015, 9, 221–229. [Google Scholar]
  34. Xuan, Y.H.; Duan, F.Y.; Je, B.I.; Kim, C.M.; Li, T.Y.; Liu, J.M.; Park, S.J.; Cho, J.H.; Kim, T.H.; von Wiren, N.; et al. Related to ABI3/VP1-Like 1 (RAVL1) regulates brassinosteroid-mediated activation of AMT1;2 in rice (Oryza sativa). J. Exp. Bot. 2016, 68, 727–737. [Google Scholar]
  35. Lamig, L.; Moreno, S.; Álvarez, J.M.; Gutiérrez, R.A. Molecular mechanisms underlying nitrate responses in plants. Curr. Biol. 2022, 32, R433–R439. [Google Scholar] [CrossRef]
  36. Galangau, F.; Daniel-vedele, F.; Moureaux, T.; Dorbe, M.F.; Leydecker, M.T.; Caboche, M. Expression of leaf nitrate reductase genes from tomato and tobacco in relation to light-dark regimes and nitrate supply. Plant Physiol. 1988, 88, 383–388. [Google Scholar] [CrossRef]
  37. Kim, J.Y.; Kwon, Y.J.; Kim, S.-I.; Kim, D.Y.; Song, J.T.; Seo, H.S. Ammonium Inhibits Chromomethylase 3-Mediated Methylation of the Arabidopsis Nitrate Reductase Gene NIA2. Front. Plant Sci. 2016, 6, 168430. [Google Scholar] [CrossRef]
  38. Han, R.-c.; Xu, Z.-r.; Li, C.-y.; Rasheed, A.; Pan, X.-h.; Shi, Q.-h.; Wu, Z.-m. The removal of nitrate reductase phosphorylation enhances tolerance to ammonium nitrogen deficiency in rice. J. Integr. Agric. 2022, 21, 631–643. [Google Scholar] [CrossRef]
  39. He, W.; Wang, L.; Lin, Q.; Feng, Y. Rice seed storage proteins: Biosynthetic pathways and the effects of environmental factors. J. Integr. Plant Biol. 2021, 63, 1999–2019. [Google Scholar] [CrossRef]
  40. Kulaeva, O.N.; Burkhanova, E.A.; Fedina, A.B.; Khokhlova, V.A.; Bokebayeva, G.A.; Vorbrodt, H.-M.; Adam, G.N. Effect of brassinosteroids on protein synthesis and plant-cell ultrastructure under stress conditions. ACS Symp. Ser. 1991, 474, 141–155. [Google Scholar] [CrossRef]
  41. Zhang, G.; Liu, Y.; Xie, Q.; Tong, H.; Chu, C. Crosstalk between brassinosteroid signaling and variable nutrient environments. Sci. China Life Sci. 2023, 66, 1231–1244. [Google Scholar]
  42. Qin, X.; Li, X.; Xiao, J.; Wu, Q.; Li, Y.; Li, C.; Jiang, D.; Tang, T.; Nan, W.; Liang, Y.; et al. Transcriptomic and Physiological Analyses of Two Rice Restorer Lines under Different Nitrogen Supplies Provide Novel Insights into Hybrid Rice Breeding. Plants 2023, 12, 2276. [Google Scholar] [CrossRef]
  43. Qiao, Y.; Yin, L.; Wang, B.; Ke, Q.; Deng, X.; Wang, S. Melatonin promotes plant growth by increasing nitrogen uptake and assimilation under nitrogen deficient condition in winter wheat. Plant Physiol. Biochem. 2019, 139, 342–349. [Google Scholar] [CrossRef]
  44. Mohn, M.A.; Thaqi, B.; Fischer-Schrader, K. Isoform-Specific NO Synthesis by Arabidopsis thaliana Nitrate Reductase. Plants 2019, 8, 67. [Google Scholar] [CrossRef] [PubMed]
  45. Corpas, F.J.; González-Gordo, S.; Palma, J.M. NO source in higher plants: Present and future of an unresolved question. Trends Plant Sci. 2022, 27, 116–119. [Google Scholar] [CrossRef]
  46. Astier, J.; Gross, I.; Durner, J. Nitric oxide production in plants: An update. J. Exp. Bot. 2018, 69, 3401–3411. [Google Scholar] [PubMed]
  47. Piacentini, D.; Della Rovere, F.; Lanni, F.; Cittadini, M.; Palombi, M.; Fattorini, L.; Cecchetti, V.; Altamura, M.M.; Falasca, G. Brassinosteroids interact with nitric oxide in the response of rice root systems to arsenic stress. Environ. Exp. Bot. 2023, 209, 105287. [Google Scholar] [CrossRef]
  48. Arredondo-Peter, R.; Moran, J.F.; Sarath, G. Rice (Oryza) hemoglobins. F1000Res 2014, 3, 253. [Google Scholar]
  49. Huwald, D.; Schrapers, P.; Kositzki, R.; Haumann, M.; Hemschemeier, A. Characterization of unusual truncated hemoglobins of Chlamydomonas reinhardtii suggests specialized functions. Planta 2015, 242, 167–185. [Google Scholar]
  50. Sanz-Luque, E.; Ocaña-Calahorro, F.; Galván, A.; Fernández, E. THB1 regulates nitrate reductase activity and THB1 and THB2 transcription differentially respond to NO and the nitrate/ammonium balance in Chlamydomonas. Plant Signal. Behav. 2015, 10, e1042638. [Google Scholar] [CrossRef]
  51. Calatrava, V.; Chamizo-Ampudia, A.; Sanz-Luque, E.; Ocaña-Calahorro, F.; Llamas, A.; Fernandez, E.; Galvan, A. How Chlamydomonas handles nitrate and the nitric oxide cycle. J. Exp. Bot. 2017, 68, 2593–2602. [Google Scholar]
Agronomy 14 00604 g002
Figure 2. Nitrate and ammonium contents of rice shoots and roots in response to BR treatment. (a,b) Nitrate content of shoots (a) and roots (b) of ZJZ17. (c,d) Nitrate content of shoots (c) and roots (d) of Nip. (e,f) Ammonium content of shoots (e) and roots (f) of ZJZ17. (g,h) Ammonium content in Nip shoots (g) and roots (h). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Figure 2. Nitrate and ammonium contents of rice shoots and roots in response to BR treatment. (a,b) Nitrate content of shoots (a) and roots (b) of ZJZ17. (c,d) Nitrate content of shoots (c) and roots (d) of Nip. (e,f) Ammonium content of shoots (e) and roots (f) of ZJZ17. (g,h) Ammonium content in Nip shoots (g) and roots (h). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Agronomy 14 00604 g002
Agronomy 14 00604 g003
Figure 3. Expression of nitrate transporter encoding genes in roots in response to BR treatment. (a–d) Relative expression of nitrate transporter (NRT) genes OsNRT1.1A (a), OsNRT1.1B (b), OsNRT2.1/OsNRT2.2 (c), and OsNRT2.4 (d) in the roots of ZJZ17. (e–h) Expression of nitrate nitrogen transporter genes OsNRT1.1A (e), OsNRT1.1B (f), OsNRT2.1/OsNRT2.2 (g), and OsNRT2.4 (h) in the roots of Nip. Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Figure 3. Expression of nitrate transporter encoding genes in roots in response to BR treatment. (a–d) Relative expression of nitrate transporter (NRT) genes OsNRT1.1A (a), OsNRT1.1B (b), OsNRT2.1/OsNRT2.2 (c), and OsNRT2.4 (d) in the roots of ZJZ17. (e–h) Expression of nitrate nitrogen transporter genes OsNRT1.1A (e), OsNRT1.1B (f), OsNRT2.1/OsNRT2.2 (g), and OsNRT2.4 (h) in the roots of Nip. Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Agronomy 14 00604 g003
Agronomy 14 00604 g004
Figure 4. Expression of ammonium transporter encoding genes in rice roots in response to BR treatment. (a–d) Relative expression of ammonium transporter (AMT) genes OsAMT1.1 (a), OsAMT1.2 (b), OsAMT1.3 (c), and OsAMT2.1 (d) in the roots of ZJZ17. (e–h) Relative expression of ammonium nitrogen transporter genes OsAMT1.1 (e), OsAMT1.2 (f), OsAMT1.3 (g), and OsAMT2.1 (h) in the roots of Nip. Values in the graphs represent means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Figure 4. Expression of ammonium transporter encoding genes in rice roots in response to BR treatment. (a–d) Relative expression of ammonium transporter (AMT) genes OsAMT1.1 (a), OsAMT1.2 (b), OsAMT1.3 (c), and OsAMT2.1 (d) in the roots of ZJZ17. (e–h) Relative expression of ammonium nitrogen transporter genes OsAMT1.1 (e), OsAMT1.2 (f), OsAMT1.3 (g), and OsAMT2.1 (h) in the roots of Nip. Values in the graphs represent means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Agronomy 14 00604 g004
Agronomy 14 00604 g005
Figure 5. Nitrate reductase (NR) and GS (glutamine synthetase) activities in rice shoots and roots. (a,b) NR activities in shoots (a) and roots (b) of ZJZ17. (c,d) NR activities in shoots (c) and roots (d) of Nip. (e,f) GS activity of ZJZ17 shoots (e) and roots (f). (g,h) GS activity of Nip shoots (g) and roots (h). Values in the graphs represent means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Figure 5. Nitrate reductase (NR) and GS (glutamine synthetase) activities in rice shoots and roots. (a,b) NR activities in shoots (a) and roots (b) of ZJZ17. (c,d) NR activities in shoots (c) and roots (d) of Nip. (e,f) GS activity of ZJZ17 shoots (e) and roots (f). (g,h) GS activity of Nip shoots (g) and roots (h). Values in the graphs represent means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Agronomy 14 00604 g005
Agronomy 14 00604 g006
Figure 6. Expression analysis of genes related to NR in rice shoots and roots in response to BR. (a,b) Relative expression of OsNIA1, OsNIA2, and OsNIA3 in shoots of ZJZ17 (a) and Nip (b). (c,d) Relative expression of OsNIA1, OsNIA2, and OsNIA3 in the roots of ZJZ17 (c) and Nip (d). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level, ns represents no significant difference).
Figure 6. Expression analysis of genes related to NR in rice shoots and roots in response to BR. (a,b) Relative expression of OsNIA1, OsNIA2, and OsNIA3 in shoots of ZJZ17 (a) and Nip (b). (c,d) Relative expression of OsNIA1, OsNIA2, and OsNIA3 in the roots of ZJZ17 (c) and Nip (d). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level, ns represents no significant difference).
Agronomy 14 00604 g006
Agronomy 14 00604 g007
Figure 7. Expression of GS genes in rice shoots and roots affected by BR treatment. (a,b) Relative expression levels of OsGS1.1, OsGS1.2, OsGS1.3, and OsGS2 in shoots of ZJZ17 (a) and Nip (b). (c,d) Relative expression of OsGS1.1, OsGS1.2, OsGS1.3, and OsGS2 in the roots of ZJZ17 (c) and Nip (d). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level, ns represents no significant difference).
Figure 7. Expression of GS genes in rice shoots and roots affected by BR treatment. (a,b) Relative expression levels of OsGS1.1, OsGS1.2, OsGS1.3, and OsGS2 in shoots of ZJZ17 (a) and Nip (b). (c,d) Relative expression of OsGS1.1, OsGS1.2, OsGS1.3, and OsGS2 in the roots of ZJZ17 (c) and Nip (d). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level, ns represents no significant difference).
Agronomy 14 00604 g007
Agronomy 14 00604 g008
Figure 8. Total free amino acid content of rice in response to BR treatment. (a,b) Total free amino acid content of shoots (a) and roots (b) of ZJZ17. (c,d) Total free amino acid content of Nip shoots (c) and roots (d). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Figure 8. Total free amino acid content of rice in response to BR treatment. (a,b) Total free amino acid content of shoots (a) and roots (b) of ZJZ17. (c,d) Total free amino acid content of Nip shoots (c) and roots (d). Values in the graphs are means ± SD (n = 3, * indicates significant difference at p < 0.05 level, ** indicates significant difference at p < 0.01 level).
Agronomy 14 00604 g008
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Yang, W.; Wan, G.-F.; Zhou, J.-Q.; Song, G.-C.; Zhao, J.; Huang, F.-L.; Meng, S. The Effects of Brassinosteroids on Nitrogen Utilization in Rice. Agronomy 2024, 14, 604. https://doi.org/10.3390/agronomy14030604

AMA Style

Yang W, Wan G-F, Zhou J-Q, Song G-C, Zhao J, Huang F-L, Meng S. The Effects of Brassinosteroids on Nitrogen Utilization in Rice. Agronomy. 2024; 14(3):604. https://doi.org/10.3390/agronomy14030604

Chicago/Turabian Style

Yang, Wei, Guo-Feng Wan, Jia-Qi Zhou, Gen-Cai Song, Jing Zhao, Feng-Lin Huang, and Shuan Meng. 2024. "The Effects of Brassinosteroids on Nitrogen Utilization in Rice" Agronomy 14, no. 3: 604. https://doi.org/10.3390/agronomy14030604

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop