Search Results (251)

To investigate how far-red (FR) light affects tobacco leaf growth, we established different light conditions, namely, CK: white (WL), T1: red (R), T2: red–white (R+WL) combination, T3: white–far-red (WL+FR) combination, and T4: white–red–far-red (WL+R+FR) combination; conducted supplemental light experiments on tobacco; and evaluated the growth of tobacco leaves by determining the biomass, size of the leaves, etc. In addition, the auxin (IAA) content and expression of leaf growth-related genes were examined to further reveal the mechanism of the FR regulation of tobacco leaf growth. The results show a maximum reduction in leaf area size of more than 90% and in fresh dry mass of more than 85%, while the chlorophyll content increased by more than 28%. in tobacco leaves exposed to FR compared with those exposed to white light. Meanwhile, levels of auxin IAA were increased by 113% (T3) and 17% (T4) under far-red light treatment. The anatomical structure of the tobacco leaves showed that FR reduced the number of epidermal cells in the leaves but increased the cell size. Subsequent findings revealed that FR’s impact on leaf growth was mediated through the PHYB–PIF7–IAA signaling pathway, wherein it regulated cell division and growth-related genes. This substantiates that FR diminishes the tobacco leaf area by impeding cell division rather than inhibiting cell growth. In this study, we explored the effects of far-red (FR) light on tobacco leaf growth changes and constructed a model of the related signaling pathways. Our results reveal a novel mechanism by which far-red light regulates the growth of tobacco leaves, elucidating how far-red light affects their growth and response to shading conditions. This finding not only provides a scientific basis for the optimization of high-density tobacco planting but also helps to improve photosynthetic efficiency and yield, providing strong support for the sustainable development of tobacco farming. Full article

Barley leaf stripe, caused by Pyrenophora graminea (Pg), significantly reduces yields across various regions globally. Understanding the resistance mechanisms of barley to Pg is crucial for advancing disease resistance breeding efforts. In this study, two barley genotypes—highly susceptible Alexis and immune Ganpi2—were inoculated with the highly pathogenic Pg isolate QWC for 7, 14, and 18 days. The number of differentially expressed genes (DEGs) in Alexis was 1350, 1898, and 2055 at 7, 14, and 18 days, respectively, while Ganpi2 exhibited 1195, 1682, and 2225 DEGs at the same time points. Gene expression pattern analysis revealed that Alexis responded more slowly to Pg infection compared to Ganpi2. A comparative analysis identified 457 DEGs associated with Ganpi2’s immunity to Pg. Functional enrichment of these DEGs highlighted the involvement of genes related to plant-pathogen interactions and kinase activity in Pg immunity. Additionally, 20 resistance genes and 24 transcription factor genes were predicted from the 457 DEGs. Twelve candidate genes were selected for qRT-PCR verification, and the results showed that the transcriptomic data was reliable. We conducted cloning of the candidate Pg resistance gene HvLRR_8-1 by the barley cultivar Ganpi2, and the sequence analysis confirmed that the HvLRR_8-1 gene contains seven leucine-rich repeat (LRR) domains and an S_TKc domain. Subcellular localization in tobacco indicates that the HvLRR_8-1 is localized on the cell membrane. Through the functional analysis using virus-induced gene silencing, it was demonstrated that HvLRR_8-1 plays a critical role in regulating barley resistance to Pg. This study represents the first comparative transcriptome analysis of barley varieties with differing responses to Pg infection, providing that HvLRR_8-1 represents a promising candidate gene for improving durable resistance against Pg in cultivated barley. Full article

The application of image recognition technology plays a vital role in agricultural disease identification. Existing approaches primarily rely on image classification, object detection, or semantic segmentation. However, a major challenge in current semantic segmentation methods lies in accurately identifying small target objects. In this study, common tobacco leaf diseases—such as frog-eye disease, climate spots, and wildfire disease—are characterized by small lesion areas, with an average target size of only 32 pixels. This poses significant challenges for existing techniques to achieve precise segmentation. To address this issue, we propose integrating two attention mechanisms, namely cross-feature map attention and dual-branch attention, which are incorporated into the semantic segmentation network to enhance performance on small lesion segmentation. Moreover, considering the lack of publicly available datasets for tobacco leaf disease segmentation, we constructed a training dataset via image splicing. Extensive experiments were conducted on baseline segmentation models, including UNet, DeepLab, and HRNet. Experimental results demonstrate that the proposed method improves the mean Intersection over Union (mIoU) by 4.75% on the constructed dataset, with only a 15.07% increase in computational cost. These results validate the effectiveness of our novel attention-based strategy in the specific context of tobacco leaf disease segmentation. Full article

Fe deficiency in apple trees can lead to leaf chlorosis and impede root development, resulting in significant alterations in signaling, metabolism, and genetic functions, which severely restricts fruit yield and quality. It is well established that WRKY transcription factors (TFs) are of vital significance in mediating plant responses to abiotic stress. Real-time quantitative fluorescence (RT-qPCR) analysis displayed that Fe deficiency stress can significantly induce WRKY69 TF gene expression. However, the potential mechanisms by which the WRKY69 gene involved in Fe deficiency stress remains to be investigated. To address this limitations, the WRKY69 gene (MD09G1235100) was successfully isolated from apple rootstock Malus halliana and performed both homologous and heterologous expression analyses in apple calli and tobacco to elucidate its functional role in response to Fe deficiency stress. The findings indicated that transgenic tobacco plants exhibited enhanced growth vigor and reduced chlorosis when subjected to Fe deficiency stress compared to the wild type (WT). Additionally, the apple calli that were overexpressed WRKY69 also exhibited superior growth and quality. Furthermore, the overexpression of the WRKY69 gene enhanced the ability of tobacco to Fe deficiency stress tolerance by stimulating the synthesis of photosynthetic pigments, increasing antioxidant enzyme activity, and facilitating Fe reduction. Additionally, it increased the resistance of apple calli to Fe deficiency stress by enhancing Fe reduction and elevating the activity of antioxidant enzymes. For example, under Fe deficiency stress, the proline (Pro) contents of the overexpression lines (OE-2, OE-5, OE-6) were 26.18 mg·g⁻¹, 26.13 mg·g⁻¹, and 26.27 mg·g⁻¹, respectively, which were 16.98%, 16.76%, and 17.38% higher than the proline content of 22.38 mg·g⁻¹ in the wild-type lines, respectively. To summarize, a functional analysis of tobacco plants and apple calli displayed that WRKY69 TF serves as a positive regulator under Fe deficiency stress, which provides candidate genetic resources for cultivating apple rootstocks or varieties with strong stress (Fe deficiency) resistance. Full article

Hemerocallis spp. exhibit distinct flower opening times, categorized into nocturnal and diurnal types. Previous studies have demonstrated that the circadian clock and CONSTANS (CO) genes play crucial roles in regulating flowering in Hemerocallis. However, the key genes that integrate flowering pathways remain largely unknown. To address this gap, we identified potential homologs of the FLOWERING LOCUS T (FT) gene in Hemerocallis. A yeast one-hybrid assay revealed that HfCOL2 and HfLHY directly bind to the HfFT1 and HfFT2 promoters, thereby activating FT transcription. The expression analysis reveals that HfCOL2 expression rhythms not only display opposing patterns between nocturnal and diurnal opening types of Hemerocallis but also between leaf and flower tissues. The peak expression of HfCOL2 in flowers aligns closely with the respective opening times of diurnally and nocturnally flowering Hemerocallis. The overexpression of HfCOL2 in tobacco plants led to early flowering and prolonged flower longevity. In Hemerocallis, the HfCOL2 gene plays a pivotal role not only in photoperiod-induced flowering but also in the circadian rhythm-mediated regulation of flower opening time. Due to the limited availability of plant materials exhibiting distinct flower opening rhythms, research in this area has been constrained. Identifying the key genes in the flowering pathway of Hemerocallis can facilitate a better understanding of the mechanisms by which plants respond to circadian rhythms. Full article

Apple (Malus domestica Borkh.) is an economically important fruit. The use of nitrate by plants plays a crucial role in their growth and development, and its absorption and dispersal are controlled by nitrate transport proteins (NRTs). In this study, we investigated the potential function of MdNRT2.4 under low-nitrogen (N) stress by overexpressing it in tobacco. Compared with plants treated with a normal nitrogen level (5 mM), the MdNRT2.4 overexpression lines under low-N stress (0.25 mM) exhibited significantly greater plant height and width, as well as larger leaves and a higher leaf density, than wild-type plants, suggesting that the overexpression of MdNRT2.4 enhances the low-N tolerance of tobacco. Enhanced antioxidant enzyme activities in the MdNRT2.4 overexpression plant lines promoted the scavenging of reactive oxygen species, which reduced damage to their cell membranes. GUS staining of pMdNRT2.4::GUS-transformed Arabidopsis thaliana lines showed that MdNRT2.4 was expressed in the roots, vascular bundles, seeds in fruit pods, and young anther sites, suggesting that MdNRT2.4 mediates the transport of nitrate to these tissues, indicating that MdNRT2.4 might promote nitrate utilization in apple and improve its tolerance to low-N stress. Experiments using yeast one-hybrid and dual-luciferase assays revealed that MdbHLH3 binds to the MdNRT2.4 promoter and activates its expression. MdbHLH3 belongs to the basic helix–loop–helix (bHLH) transcription factor (TF). It is speculated that MdbHLH3 may interact with the promoter of MdNRT2.4 to regulate N metabolism in plants and enhance their low-N tolerance. This study establishes a theoretical framework for investigating the regulatory mechanisms of low-N responsive molecules in apple, while simultaneously providing valuable genetic resources for molecular breeding programs targeting low-N tolerance. Full article

Plant defensin (PDF/DEF), an important pathogenesis-related protein which widely exists in plants, displays broad-spectrum antifungal activities. To date, however, reports on the banana PDFs are very limited. In this study, we identified, cloned, and characterized the five Class I PDFs (MaPDF2.1~MaPDF2.5) in banana (Musa acuminata). Further, their expression in root, corm, leaf, and fruit were studied. MaPDFs exhibited quite different expression patterns in different organs, with MaPDF2.2 as the only member expressing in all the tested organs, and its expression levels in all organs were the highest among all MaPDFs. The MaPDF2.2 expression could be significantly upregulated by both low- and high-temperature stresses but significantly downregulated by the inoculations of plant growth promoting endophytic fungus Serendipita indica and banana Fusarium wilt (FW) pathogen Fusarium oxysporum f. sp. cubense (Foc) Tropical race 4 (FocTR4). Moreover, the S. indica pre-colonization could significantly alleviate the suppression of FocTR4 on MaPDF2.2, suggesting that this MaPDF might contribute greatly to the S. indica-enhanced FW resistance. By using tobacco leaf transient overexpression, the function of MaPDF2.2 was investigated. Its overexpression significantly inhibited the infection of Foc race 1 (Foc1) and FocTR4 in tobacco leaves. Furthermore, in vitro antifungal ability assays revealed that the recombinant His-MaPDF2.2 protein could significantly inhibit the growth of Foc1 and FocTR4, as well as the pigment accumulation of Foc1. Our study revealed the sequence and expression characteristics of banana PDFs and demonstrated the antifungal ability of MaPDF2.2 to FW pathogens. Full article

Background/Objectives: Plants release extracellularly lipid bilayer-enclosed vesicles of nanometric size that can be retrieved in their fluids. Plant-derived extracellular vesicles (PDEVs) have mostly been involved in modulating host–pathogen interaction, making them a tool for cross-kingdom communication with a key role in plant immunity. In addition, PDEVs have demonstrated promising therapeutic features, not only in terms of intrinsic nutraceutical properties but also of active molecules’ delivery. Transgenic plants have been developed for a variety of purposes, i.e., to improve their functional properties like crops, but also to produce therapeutic molecules. However, it is unclear whether transgenes can end up in PDEVs, thus making them a vehicle for their cross-kingdom diffusion into the environment. Methods: Here, we investigated the association of transgenic DNA and RNA with PDEVs secreted by tobacco (Nicotiana tabacum) engineered to express the neomycine phosphotransferase II (Npt-II) gene. PDEVs were isolated from leaf apoplastic fluid by ultracentrifugation and characterized for their morphology and size. The association of DNA and RNA was assessed by qRT-PCR and their immunomodulatory properties by assaying PDEVs-induced IL1β and IL10 on THP1 monocytes. Results: Npt-II RNA, but not DNA, could be amplified from PDEVs, whereas no differences were observed between wt and transgenic tobacco PDEVs in terms of immunomodulatory properties. Conclusions: Although a different behaviour by other types of RNAs or DNAs could still be possible, our findings indicate that in this model, PDEVs are not associated with transgenic DNA, but they can protect RNA, including transgenic RNA, from degradation, contributing to their cross-kingdom spreading. Full article

In metabolically engineered plants, the target products are usually uniformly distributed in the whole plant or specific tissues. When engineering tobacco to produce astaxanthin, a ketocarotenoid with strong antioxidant activity and multiple bioactivities, a scattered distribution of astaxanthin-producing regions was observed in a small portion of astaxanthin-producing tobacco plants, which caused mosaic-like red and green spots on the leaves (ASTA-mosaic). A physiological assay showed that the non-astaxanthin green region (Mosaic_G) had relatively higher chlorophyll content and better chloroplast structure than the astaxanthin-producing red region (Mosaic_R). Then, metabolomics, proteomics, and small RNA transcriptomics were employed to analyze the uneven distribution of astaxanthin-producing regions in tobacco leaves. The results of metabolomics and proteomics revealed a decrease in carotenoid metabolism, chlorophyll biosynthesis, and chlorophyll degradation in the Mosaic_G region. Pheophorbide a, an intermediate of chlorophyll degradation, was found to be significantly reduced in the Mosaic_G region, which was accompanied by the attenuation of chlorophyllase and pheophytinase, which catalyze the formation of pheophorbide a in chlorophyll degradation. Reductions in photosynthetic antenna proteins and photosystem-associated proteins were observed in the Mosaic_R region, consistent with the better chloroplast structure of the Mosaic_G region. Small RNA transcriptomics showed that several small RNAs could target chlorophyll-degradative genes, but they were more effective in targeting the astaxanthin biosynthetic genes. This finding was supported by the fact that the Mosaic_G region can remain green up to the senescence of tobacco leaves. This work provides insights into the mechanism of the uneven distribution of astaxanthin-producing regions in tobacco leaves and may contribute to the specialized utilization of tobacco plants for metabolic engineering. Full article

Hop latent viroid (HLVd), a 256-nucleotide RNA strand with complementary base-pairing and internal stem loop structures, forms circular or rod-shaped molecules within diseased plants. RT-PCR/RT-qPCR was used to assess HLVd transmission, spread and longevity. The viroid was detected in asymptomatic stock plants and in rooted vegetative cuttings, as well as in recirculated nutrient solution sampled from propagation tables and nozzles. Plant-to-plant spread through root infection in hydroponic cultivation was demonstrated. The viroid survived for 7 days and 4 weeks, respectively, in crushed leaf extracts (sap) or dried leaves/roots at room temperature. Following stem inoculation with infectious sap, HLVd was detected in root tissues within 2–3 weeks and in the foliage within 4–6 weeks. Plants grown under a 12:12 h photoperiod to induce inflorescence development showed more rapid spread of HLVd compared to 24 h lighting. The viroid was subsequently detected in inflorescence tissues, in trichome glands, in dried cannabis flowers and in crude resinous oil extracts. Anthers and pollen from infected male plants and seeds from infected female plants contained HLVd, giving rise to up to 100% infected seedlings. Artificially inoculated tomato and tobacco plants supported viroid replication in roots and leaves. Infected cannabis leaf and root tissues treated with UV-C for 3–5 min or temperatures of 70–90 °C for 30 min contained amplifiable HLVd-RNA. Infectious plant extract treated with 5–10% bleach (0.825% NaOCl) or 1000 ppm hypochlorous acid yielded no RT-PCR bands, suggesting the RNA was degraded. Meristem tip culture from HLVd-infected plants yielded a high frequency of pathogen-free plants, depending on the genotype. Full article

Uneven heating is the biggest obstacle to the application of radio frequency (RF) technology in insecticidal applications. Since many existing studies have focused on the RF heating uniformity of granular materials, few RF treatment solutions have been reported for leaf materials. To improve the RF heating uniformity of tobacco leaves, a combined RF-hot air treatment method was developed for disinfestation in this study. The experiments were conducted to determine the effects of three process parameters (electrode gap, sample thickness, and hot air temperature) on the RF heating rate and uniformity of tobacco leaves. The results showed that the heating rate of RF-hot air combined treatment increased with decreasing electrode gap but increased with increasing sample thickness and hot air temperature. The RF heating uniformity in tobacco leaves decreased with increasing heating rate but could be significantly improved with the conveyor movement. Considering the heating uniformity and heating rate, the material thickness of 60 mm and electrode gap of 110 mm were selected as optimal process parameters. The results of the study may provide a feasible method to improve the RF heating uniformity in tobacco leaves and potential applications for effective disinfestations. Full article

Salt stress is a major abiotic stress that interferes with plant growth and affects crop production. Dehydrin (DHN), a member of the late embryogenesis abundant (LEA) protein family, was considered to be a stress protein involved in the protective reaction of plant dehydration. Our previous research has shown that overexpression of the Suaeda salsa SsDHN gene enhances tolerance to salt stress in tobacco. However, the research on its protection in photosynthesis under salt stress remains unclear. In this study, gene overexpression (SsDHN-OE) tobacco plants were utilized to study the effect of the SsDHN gene on plant photosynthesis under salt stress. Our findings showed that overexpression of SsDHN increased the biomass, leaf area, root length, and root surface area in tobacco seedlings under salt stress conditions. The transgenic tobacco with overexpression of SsDHN had obvious stomatal closure, which effectively alleviated the adverse effects of salt stress on photosynthetic efficiency. Overexpression of the SsDHN gene in tobacco can effectively reduce the degree of photoinhibition and chloroplast damage caused by salt stress. Moreover, the SsDHN-overexpressing transgenic tobacco plants exhibited a decrease in oxidative damage and protected membrane structures related to photosynthesis by increasing antioxidant enzyme activity and antioxidant substance content. It was further found that the expression levels of photosynthetic and antioxidant-related genes Rubisco, SBPase, POD7, CAT3, APX2, and SOD3 were significantly up-regulated by overexpressing the SsDHN gene in tobacco seedlings under salt stress. In conclusion, the SsDHN gene might improve the salt stress resistance of tobacco seedlings and be involved in regulating photosynthesis and antioxidant activity under salt stress. Full article

Tomato yellow leaf curl virus (TYLCV) poses a significant threat to tomato production, leading to severe yield losses. The current control strategies primarily rely on the use of pesticides, which are often nonselective and costly. Therefore, there is an urgent need to identify more environmentally friendly alternatives. Dufulin, a novel compound that has been effective in controlling viral diseases in tobacco and rice, has not yet been tested against TYLCV. This study assessed the efficacy of dufulin in controlling TYLCV over a three-year span from 2021 to 2023 through field trials, by monitoring disease symptoms and viral titers. Additionally, this study assessed the expression levels of genes associated with systemic acquired resistance (SAR), specifically proteinase inhibitor II (PI II) and non-expressor of pathogenesis-related genes 1 (NPR1), using real-time qRT-PCR. The chlorophyll and nitrogen content in the leaves were also measured. Plants treated with dufulin showed reduced symptomatology and lower viral titers compared to the controls. Analysis of gene expression revealed that NPR1 was upregulated in the dufulin-treated plants, whereas PI II expression was consistently downregulated in the TYLCV-infected plants. Interestingly, PI II expression increased in the healthy plants following a seven-day post-treatment with dufulin. Moreover, the treated plants exhibited a higher chlorophyll content than the controls, though no significant differences in the nitrogen levels were observed between the dufulin-treated and water-treated plants. Overall, the application of dufulin significantly bolstered the plant’s defense response, effectively reducing TYLCV symptoms and enhancing resistance. Full article

Low temperature, as a major abiotic stress, impacts the formation of high-quality tobacco seedlings. It is urgent to take appropriate measures to improve the low-temperature tolerance of tobacco seedlings. A hydroponics experiment was conducted with a tobacco cv. Y2001 under 25 °C (control temperature) and 10 °C (low-temperature stress). Three phosphorus (P) levels including the traditional P concentration (2 mM PO₄³⁻) and higher P levels (3 mM PO₄³⁻ and 4 mM PO₄³⁻) were applied to investigate their effects on antioxidant metabolism and carbohydrate metabolism in low-temperature-stressed tobacco seedlings. The results showed that the low temperature decreased plant height, stem diameter, and biomass of shoots and roots, while the higher P levels promoted plant height and shoot biomass of low-temperature-stressed tobacco seedlings compared to the traditional P level. The leaf net photosynthetic rate (A_N) was decreased by the low temperature, while the A_N of low-temperature-stressed tobacco leaves was increased by 38.6–61.3% for the higher P levels than the traditional P level. Higher O₂⁻ and H₂O₂ were observed in tobacco leaves exposed to low-temperature stress, damaging the A_N, although the low temperature upregulated the expression of encoding superoxide dismutase (NtSOD), peroxidase (NtPOD), and catalase (NtCAT). However, compared with the traditional P level, the higher P levels further upregulated the expression of NtSOD and NtCAT in low-temperature-stressed tobacco leaves to accelerate O₂⁻ and H₂O₂ removal. Higher leaf sucrose content was detected since the low temperature significantly downregulated the expression of NtSuSy, NtCWINV, and NtNINV encoding sucrose synthase, the cell wall, and alkaline invertases, respectively, inhibiting sucrose hydrolysis. Compared with the traditional P level, higher P levels downregulated the expression of NtCWINV in low-temperature-stressed tobacco leaves, further promoting leaf sucrose content. The low temperature downregulated the expression of NtAGP encoding ADP-glucose pyrophosphorylase, NtSSS encoding soluble starch synthase, and NtGBSS encoding granule-bound starch synthase, thereby restricting starch biosynthesis. Additionally, the low temperature upregulated the expression of α-amylase and β-amylase, accelerating starch hydrolysis. These led to a lower starch content in low-temperature-stressed tobacco leaves. The higher P levels further upregulated the expression of α-amylase in low-temperature-stressed tobacco leaves than the traditional P level, further lowering the starch content. Moreover, the leaf soluble sugar content was higher under the low temperature than the control temperature, which helped the tobacco plants resist low-temperature stress. And higher P levels further promoted the soluble sugar content in low-temperature-stressed tobacco leaves compared with the traditional P level, further improving tobacco seedlings’ low-temperature tolerance. Therefore, these results indicated that increasing the P application level can alleviate the adverse impacts of cold stress on antioxidant metabolism and carbohydrate metabolism in tobacco seedlings. Full article

The ability of a cold-shock protein CspD from Bacillus thuringiensis to protect both dicots and monocots against various pathogens is well confirmed under both greenhouse and field conditions; however, the molecular basis of this phenomenon at the transcriptomic level still remains unexplored. Expression profiles of some marker genes associated with SAR/ISR nonspecific resistance pathways and ROS scavengers were examined in CspD-treated Nicotiana tabacum plants, and the RNA-seq analysis of CspD-treated plants was first carried out. The ISR markers PDF1.2 and PR4 were overexpressed locally in treated tobacco leaves with the maximum 2.4- and 5.7-fold change, respectively, reached 12 h after the leaf treatment with CspD; PDF1.2 was also up-regulated 4.8-fold four days after the inoculation of treated plants with TMV. The ROS scavenger analysis demonstrated overexpression of Cu-Zn superoxide dismutase in both treated (with the maximum 5.4-fold change observed 6 h after the treatment) leaves and leaves from the upper tier (“system” leaves, 6.5-fold change observed 4 days after the treatment). The ROS assay confirmed endogenous accumulation of superoxide in CspD-treated leaves 6 and 24 h after the treatment. An in silico comparative study of Arabidopsis orthologs of highly up-regulated tobacco genes induced by CspD with Arabidopsis genes activated by some other molecular patterns revealed the specific CspD-induced expression of Cu-Zn superoxide dismutase and some other genes associated with light and cold responses. This study may contribute to a better understanding of cross-talking between abiotic stress and nonspecific immunity in plants. Full article