Search Results (49)

As an endogenous hormone, auxin plays a crucial role in regulating plants’ growth and development, and also in the responses to abiotic stresses. However, the effects and mechanism of auxin and its inhibitors on plant growth and mineral nutrient absorption in citrus have not been thoroughly studied. Therefore, we used trifoliate orange (citrus’s rootstock, Poncirus trifoliata) as the experimental material to supplement the research content in this area. The trifoliate orange seedlings were treated with exogenous auxin (indolebutyric acid, IBA) and auxin inhibitor (2-naphthoxyacetic acid, 2-NOA) in a sand culture system. The results showed that compared to the control, exogenous auxin (1.0 µmol L⁻¹ IBA) significantly enhanced the taproot length, lateral root length, and lateral root number by 17.56%, 123.07%, and 88.89%, respectively, while also markedly elevating the levels of nitrogen (N), phosphorus (P), potassium (K), copper (Cu), and zinc (Zn) by 14.29%, 45.61%, 23.28%, 42.86%, and 59.80%, respectively. Again compared to the control, the auxin inhibitor (50.0 µmol L⁻¹ 2-NOA) dramatically reduced the taproot length, lateral root length, and lateral root number by 21.37%, 10.25%, and 43.33%, respectively, while also markedly decreasing the levels of N, magnesium (Mg), iron (Fe), Cu, and Zn by 7.94%, 10.42%, 24.65%, 39.25%, and 18.76%, respectively. Furthermore, IBA increased auxin accumulation in the root hair, stele, and epidermal tissues of citrus taproots, and promoted the up-regulation of auxin synthesis genes (TAR2, YUC3, YUC4, YUC6, YUC8) and transport genes (ABCB1, ABCB19, AUX1, LAX1, LAX2, PIN1, PIN3, PIN4). In contrast, 2-NOA decreased auxin levels in the root hair, stele, and epidermal tissues of citrus taproots, and was involved in the down-regulation of auxin synthesis genes (TAR2, YUC3, YUC4, YUC6) and transport genes (ABCB1, AUX1, LAX1, LAX2, LAX3, PIN3). Interestingly, 2-NOA dramatically elevated auxin level specifically in the root tip of citrus taproot. Therefore, 2-NOA disrupts auxin reflux from the root tip to root hair and epidermal tissues in citrus taproot through down-regulation of auxin transport genes, thereby creating localized (i.e., root hair zone and epidermal tissues) auxin deficiencies that compromise root system architecture and nutrient acquisition capacity. According to the results of this study, exogenous auxin analogs could regulate citrus growth and mineral nutrient absorption through the auxin synthesis and transport pathways. Full article

The embryogenic transition of plant somatic cells to produce somatic embryos requires extensive reprogramming of the cell transcriptome. The prominent role of transcription factors (TFs) and miRNAs in controlling somatic embryogenesis (SE) induction in plants was documented. The profiling of MIRNA expression in the embryogenic culture of Arabidopsis implied the contribution of the miR156 and miR169 to the embryogenic induction. In the present study, the function of miR156 and miR169 and the candidate targets, SPL and NF-YA genes, were investigated in Arabidopsis SE. The results showed that misexpression of MIRNA156 and candidate SPL target genes (SPL2, 3, 4, 5, 9, 10, 11, 13, 15) negatively affected the embryogenic potential of transgenic explants, suggesting that specific fine-tuning of the miR156 and target genes expression levels seems essential for efficient SE induction. The results revealed that SPL11 under the control of miR156 might contribute to SE induction by regulating the master regulators of SE, the LEC (LEAFY COTYLEDON) genes (LEC1, LEC2, FUS3). Moreover, the role of miR169 and its candidate NF-YA targets in SE induction was demonstrated. The results showed that several miR169 targets, including NF-YA1, 3, 5, 8, and 10, positively regulated SE. We found, that miR169 via NF-YA5 seems to modulate the expression of a master SE regulator LEC1/NF-YA and other auxin-related genes: YUCCA (YUC4, 10) and PIN1 in SE induction. The study provided new insights into miR156-SPL and miR169-NF-YA functions in the auxin-related and LEC-controlled regulatory network of SE. Full article

The research is aimed to elucidate the role of plant hormones in regulating the development of hybrid embryos in Hydrangea macrophylla. Fruits from the intraspecific cross of H. macrophylla ‘Otaksa’ × ‘Coerulea’ were selected at the globular, heart, and torpedo stages of embryo development. Transcriptome sequencing and differential gene expression analysis were conducted. The results showed that fruit growth followed a single “S-shaped growth curve, with globular, heart, and torpedo embryos appearing at 30, 40, and 50 d post-pollination, respectively, and the embryo maintaining the torpedo shape from 60 to 90 d. A total of 12,933 genes was quantified across the three developmental stages, with 3359, 3803, and 3106 DEGs in the S1_vs_S2, S1_vs_S3, and S2_vs_S3 comparisons, respectively. Among these, 133 genes related to plant hormone biosynthesis and metabolism were differentially expressed, regulating the synthesis and metabolism of eight types of plant hormones, including cytokinin, auxin, gibberellin, abscisic acid, and jasmonic acid. The pathways with the most differentially expressed genes were cytokinin, auxin, and gibberellin, suggesting these hormones may play crucial roles in embryo development. In the cytokinin pathway, CKX (Hma1.2p1_0579F.1_g182670.gene, Hma1.2p1_1194F.1_g265700.gene, and NewGene_12164) genes were highly expressed during the globular embryo stage, promoting rapid cell division in the embryo. In the auxin pathway, YUC (Hma1.2p1_0271F.1_g109005.gene and Hma1.2p1_0271F.1_g109020.gene) genes were progressively up-regulated during embryo growth; the early response factor AUX/IAA (Hma1.2p1_0760F.1_g214260.gene) was down-regulated, while the later transcriptional activator ARF (NewGene_21460, NewGene_21461, and Hma1.2p1_0209F.1_g089090.gene) was up-regulated, sustaining auxin synthesis and possibly preventing the embryo from transitioning to maturity. In the gibberellin pathway, GA3ox (Hma1.2p1_0129F.1_g060100.gene) expression peaked during the heart embryo stage and then declined, while the negative regulator GA2ox (Hma1.2p1_0020F.1_g013915.gene) showed the opposite trend; and the gibberellin signaling repressor DELLA (Hma1.2p1_1054F.1_g252590.gene) increased over time, potentially inhibiting embryo development and maintaining the torpedo shape until fruit maturity. These findings preliminarily uncover the factors affecting the development of hybrid H. macrophylla embryos, laying a foundation for further research into the regulatory mechanisms of H. macrophylla hybrid embryo development. Full article

Lateral roots (LRs) receive signals from the inter-root environment and absorb water and nutrients from the soil. Auxin regulates LR formation, but the mechanism in tomato remains largely unknown. In this study, ‘Ailsa Craig‘ tomato LRs appeared on the third day and were unevenly distributed in primary roots. According to the location of LR occurrence, roots were divided into three equal parts: the shootward part of the root (RB), the middle part of the root (RM), and the tip part of the root (RT). Transverse sections of roots from days 1 to 6 revealed that the number of RB cells and the root diameter were significantly increased compared with RM and RT. Using roots from days 1 to 3, we carried out transcriptome sequencing analysis. Identified genes were classified into 16 co-expression clusters based on K-means, and genes in four associated clusters were highly expressed in RB. These four clusters (3, 5, 8, and 16) were enriched in cellulose metabolism, microtubule, and peptide metabolism pathways, all closely related to LR development. The four clusters contain numerous transcription factors linked to LR development including transcription factors of LATERAL ORGAN BOUNDRIES (LOB) and MADS-box families. Additionally, auxin-related genes GATA23, ARF7, LBD16, EXP, IAA4, IAA7, PIN1, PIN2, YUC3, and YUC4 were highly expressed in RB tissue. Free IAA content in 3 d RB was notably higher, reaching 3.3–5.5 ng/g, relative to RB in 1 d and 2 d. The LR number was promoted by 0.1 μM of exogenous IAA and inhibited by exogenous NPA. We analyzed the root cell state and auxin signaling module during LR formation. At a certain stage of pericycle cell development, LR initiation is regulated by auxin signaling modules IAA14-ARF7/ARF19-LBD16-CDKA1 and IAA14-ARF7/ARF19-MUS/MUL-XTR6/EXP. Furthermore, as a key regulatory factor, auxin regulates the process of LR initiation and LR primordia (LRP) through different auxin signaling pathway modules. Full article

Tomato (Solanum lycopersicum) breeding for improved fruit quality emphasizes selecting for desirable taste and characteristics, as well as enhancing disease resistance and yield. Seed germination is the initial step in the plant life cycle and directly affects crop productivity and yield. ERECTA (ER) is a receptor-like kinase (RLK) family protein known for its involvement in diverse developmental processes. We characterized a Micro-Tom EMS mutant designated as a knock-out mutant of sler. Our research reveals that SlER plays a central role in controlling critical traits such as inflorescence development, seed number, and seed germination. The elevation in auxin levels and alterations in the expression of ABSCISIC ACID INSENSITIVE 3 (ABI3) and ABI5 in sler seeds compared to the WT indicate that SlER modulates seed germination via auxin and abscisic acid (ABA) signaling. Additionally, we detected an increase in auxin content in the sler ovary and changes in the expression of auxin synthesis genes YUCCA flavin monooxygenases 1 (YUC1), YUC4, YUC5, and YUC6 as well as auxin response genes AUXIN RESPONSE FACTOR 5 (ARF5) and ARF7, suggesting that SlER regulates fruit development via auxin signaling. Full article

Arbuscular mycorrhizal fungi (AMF) are known to enhance plant growth via stimulation of root system development. However, the extent of their effects and underlying mechanisms across different citrus genotypes remain to be fully elucidated. This study investigates the impact of Funneliformis mosseae (F. mosseae) inoculation on plant growth performance, root morphology, phosphorus (P), and indole-3-acetic acid (IAA) concentrations, as well as the expression of related synthesis and transporter genes in three citrus genotypes: red tangerine (Citrus tangerine ex. Tanaka), kumquat (Fortunella margarita L. Swingle), and fragrant citrus (Citrus junos Sieb. ex. Tanaka). Following 12 weeks of inoculation, significant improvements were observed in plant height, shoot and root biomass, total root length, average root diameter, second-order lateral root development, root hair density, and root hair length across all genotypes. Additionally, F. mosseae inoculation significantly increased root P and IAA concentrations in the three citrus genotypes. Notably, phosphatase activity was enhanced in F. margarita but reduced in C. tangerine and C. junos following inoculation. Gene expression analysis revealed a universal upregulation of the P transporter gene PT5, whereas expressions of the auxin synthesis gene YUC2, transporter gene LAX2, and phosphatase gene PAP1 were commonly downregulated. Specific to genotypes, expressions of YUC5, LAX5, PIN2, PIN3, PIN6, and expansin genes EXPA2 and EXPA4 were significantly upregulated in C. tangerine but downregulated in F. margarita and C. junos. Principal component analysis and correlation assessments highlighted a strong positive association between P concentration, P and auxin synthesis, and transporter gene expressions with most root morphology traits, except for root average diameter. Conversely, IAA content and phosphatase activities were negatively correlated with these root traits. These findings suggest that F. mosseae colonization notably enhances plant growth and root system architecture in citrus genotypes via modifications in P transport and IAA accumulation, indicating a complex interplay between mycorrhizal symbiosis and host plant physiology. Full article

Expansins (EXPs) loosen plant cell walls and are involved in diverse developmental processes through modifying cell-walls; however, little is known about the role of PpEXPs in peach fruit. In this study, 26 PpEXP genes were identified in the peach genome and grouped into four subfamilies, with 20 PpEXPAs, three PpEXPBs, one PpEXPLA and two PpEXPLBs. The 26 PpEXPs were mapped on eight chromosomes. The primary mode of gene duplication of the PpEXPs was dispersed gene duplication (DSD, 50%). Notably, cis-elements involved in light responsiveness and MeJA-responsiveness were detected in the promoter regions of all PpEXPs, while ethylene responsive elements were observed in 12 PpEXPs. Transcript profiling of PpEXPs in the peach fruit varieties of MF (melting), NMF (non-melting) and SH (stony hard) at different stages showed that PpEXPs displayed distinct expression patterns. Among the 26 PpEXPs, 15 PpEXPs were expressed in the fruit. Combining the expressing patterns of PpEXPs in fruits with different flesh textures, PpEXPA7, PpEXPA13 and PpEXPA15 were selected as candidate genes, as they were highly consistent with the patterns of previous reported key genes (PpPGM, PpPGF and PpYUC11) in regard to peach fruit texture. The genes with different expression patterns between MF and NMF were divided into 16 modules, of which one module, with pink and midnightblue, negatively correlated with the phenotype of fruit firmness and was identified as PpEXPA1 and PpEXPA7, while the other module was identified as PpERF in the pink module, which might potentially effect fruit texture development by regulating PpEXPs. These results provide a foundation for the functional characterization of PpEXPs in peach. Full article

Auxin amino acid conjugates are considered to be storage forms of auxins. Previous research has shown that indole-3-acetyl-L-alanine (IAA-Ala), indole-3-propionyl-L-alanine (IPA-Ala) and indole-3-butyryl-L-alanine (IBA-Ala) affect the root growth of Brassica rapa seedlings. To elucidate the potential mechanism of action of the conjugates, we treated B. rapa seedlings with 0.01 mM IAA-, IPA- and IBA-Ala and investigated their effects on the auxin metabolome and transcriptome. IBA-Ala and IPA-Ala caused a significant inhibition of root growth and a decrease in free IAA compared to the control and IAA-Ala treatments. The identification of free auxins IBA and IPA after feeding experiments with IBA-Ala and IPA-Ala, respectively, confirms their hydrolysis in vivo and indicates active auxins responsible for a stronger inhibition of root growth. IBA-Ala caused the induction of most DEGs (807) compared to IPA-Ala (417) and IAA-Ala (371). All treatments caused similar trends in transcription profile changes when compared to control treatments. The majority of auxin-related DEGs were found after IBA-Ala treatment, followed by IPA-Ala and IAA-Ala, which is consistent with the apparent root morphology. In addition to most YUC genes, which showed a tendency to be downregulated, transcripts of auxin-related DEGs that were identified (UGT74E2, GH3.2, SAUR, IAA2, etc.) were more highly expressed after all treatments. Our results are consistent with the hypothesis that the hydrolysis of conjugates and the release of free auxins are responsible for the effects of conjugate treatments. In conclusion, free auxins released by the hydrolysis of all auxin conjugates applied affect gene regulation, auxin homeostasis and ultimately root growth inhibition. Full article

Cotton growth and yield are severely affected by abiotic stress worldwide. Mepiquate chloride (MC) and melatonin (MT) enhance crop growth and yield by reducing the negative effects of abiotic stress on various crops. Numerous studies have shown the pivotal role of MC and MT in regulating agricultural growth and yield. Nevertheless, an in-depth review of the prominent performance of these two hormones in controlling plant morpho-physiological activity and yield in cotton under abiotic stress still needs to be documented. This review highlights the effects of MC and MT on cotton morpho-physiological and biochemical activities; their biosynthetic, signaling, and transduction pathways; and yield under abiotic stress. Furthermore, we also describe some genes whose expressions are affected by these hormones when cotton plants are exposed to abiotic stress. The present review demonstrates that MC and MT alleviate the negative effects of abiotic stress in cotton and increase yield by improving its morpho-physiological and biochemical activities, such as cell enlargement; net photosynthesis activity; cytokinin contents; and the expression of antioxidant enzymes such as catalase, peroxidase, and superoxide dismutase. MT delays the expression of NCED1 and NCED2 genes involved in leaf senescence by decreasing the expression of ABA-biosynthesis genes and increasing the expression of the GhYUC5, GhGA3ox2, and GhIPT2 genes involved in indole-3-acetic acid, gibberellin, and cytokinin biosynthesis. Likewise, MC promotes lateral root formation by activating GA20x genes involved in gibberellin catabolism. Overall, MC and MT improve cotton’s physiological activity and antioxidant capacity and, as a result, improve the ability of the plant to resist abiotic stress. The main purpose of this review is to present an in-depth analysis of the performance of MC and MT under abiotic stress, which might help to better understand how these two hormones regulate cotton growth and productivity. Full article

Significant progress has been made in the functions of auxin efflux transporter PIN-FORMED (PIN) genes for the regulation of growth and development in rice. However, knowledge on the roles of OsPIN genes in abiotic stresses is limited. We previously reported that the mutation of OsPIN1b alters rice architecture and root gravitropism, while the role of OsPIN1b in the regulation of rice abiotic stress adaptations is still largely elusive. In the present study, two homozygous ospin1b mutants (C1b-1 and C1b-2) were employed to investigate the roles of OsPIN1b in regulating abiotic stress adaptations. Low temperature gradually suppressed OsPIN1b expression, while osmotic stress treatment firstly induced and then inhibited OsPIN1b expression. Most OsPIN genes and auxin biosynthesis key genes OsYUC were up-regulated in ospin1b leaves, implying that auxin homeostasis is probably disturbed in ospin1b mutants. The loss of function of OsPIN1b significantly decreased rice chilling tolerance, which was evidenced by decreased survival rate, increased death cells and ion leakage under chilling conditions. Compared with the wild-type (WT), ospin1b mutants accumulated more hydrogen peroxide (H₂O₂) and less superoxide anion radicals $\left({\mathrm{O}}_2^{-}\right)$ after chilling treatment, indicating that reactive oxygen species (ROS) homeostasis is disrupted in ospin1b mutants. Consistently, C-repeat binding factor (CBF)/dehydration-responsive element binding factor (DREB) genes were downregulated in ospin1b mutants, implying that OsDREB genes are implicated in OsPIN1b-mediated chilling impairment. Additionally, the mutation of OsPIN1b led to decreased sensitivity to abscisic acid (ABA) treatment in seed germination, impaired drought tolerance in the seedlings and changed expression of ABA-associated genes in rice roots. Taken together, our investigations revealed that OsPIN1b is implicated in chilling and drought tolerance in rice and provide new insight for improving abiotic stress tolerance in rice. Full article

Although recent research progress on the abundant C-to-U RNA editing events in plant chloroplasts and mitochondria has uncovered many recognition factors and their molecular mechanisms, the intrinsic regulation of RNA editing within plants remains largely unknown. This study aimed to establish a regulatory relationship in Arabidopsis between the plant hormone auxin and chloroplast RNA editing. We first analyzed auxin response elements (AuxREs) present within promoters of chloroplast editing factors reported to date. We found that each has more than one AuxRE, suggesting a potential regulatory role of auxin in their expression. Further investigation unveiled that the depletion of auxin synthesis gene YUC2 reduces the expression of several editing factors. However, in yuc2 mutants, only the expression of CRR4, DYW1, ISE2, and ECD1 editing factors and the editing efficiency of their corresponding editing sites, ndhD-2 and rps14-149, were simultaneously suppressed. In addition, exogenous IAA and the overexpression of YUC2 enhanced the expression of these editing factors and the editing efficiency at the ndhD-2 and rps14-149 sites. These results suggested a direct effect of auxin upon the editing of the ndhD-2 and rps14-149 sites through the modulation of the expression of the editing factors. We further demonstrated that ARF1, a downstream transcription factor in the auxin-signaling pathway, could directly bind to and inactivate the promoters of CRR4, DYW1, and ISE2 in a dual-luciferase reporter system, thereby inhibiting their expression. Moreover, the overexpression of ARF1 in Arabidopsis significantly reduced the expression of the three editing factors and the editing efficiency at the ndhD-2 and rps14-149 sites. These data suggest that YUC2-mediated auxin biosynthesis governs the RNA-editing process through the ARF1-dependent signal transduction pathway. Full article

In common with other plant species, the garden pea (Pisum sativum) produces the auxin indole-3-acetic acid (IAA) from tryptophan via a single intermediate, indole-3-pyruvic acid (IPyA). IPyA is converted to IAA by PsYUC1, also known as Crispoid (Crd). Here, we extend our understanding of the developmental processes affected by the Crd gene by examining the phenotypic effects of crd gene mutations on leaves, flowers, and roots. We show that in pea, Crd/PsYUC1 is important for the initiation and identity of leaflets and tendrils, stamens, and lateral roots. We also report on aspects of auxin deactivation in pea. Full article

Plant tissue regeneration is a key process for genetic transformation and genome editing. The exploration of regulatory mechanisms in plant regeneration would improve regeneration efficiency. In comparison to some model plants, the genomic heterozygosity is much higher in forest trees, increasing the complexity of transcriptional regulation. Here, we report the allele-specific transcriptional analysis in hybrid poplar 84K (Populus alba × P. tremula var. glandulosa cv. 84K) during the shoot regeneration process. Firstly, 180 regeneration-related genes (REGs) and 2446 REG-homologous genes (REGHs) were identified in hybrid poplar. The expression patterns of REGs exhibited that about half of them were positively correlated between poplar and Arabidopsis at the locus level. The expression levels of REGHs vary among the gene family at different stages during callus and shoot induction. Among the gene clusters with similar expression patterns, the distribution of gene families in poplar and Arabidopsis also exhibits large variations. At the allele level, most of the allele pairs of REGs were positively correlated in expression. The expression patterns of genes in auxin synthesis, transport, and signaling pathways agree with the general patterns. Due to the presence/absence of variations between two subgenomes, two YUC alleles and two IAA alleles are present only in one subgenome, and the expression patterns of the two alleles are greatly different. Our analysis indicates the conservativeness and diversity of transcriptional regulation during shoot regeneration in poplar and Arabidopsis. The complexity in allele expression contributed by heterozygosity suggests the importance of genotyping in the screening of explants for plant regeneration. Full article

The tea plant is a perennial leaf-used economical crop and cultivated all over the world. Indole-3-acetic acid (IAA) plays key roles in plant development and environmental stress. YUCCA (YUC) flavin monooxygenases are the rate-limiting enzymes of the TAA/YUC pathway, which is the most important IAA biosynthetic pathway in plants. The YUC gene family in tea plants has not been systematically studied so far. A total of 17 CsYUC members were identified from a tea plant genome database and phylogenetically classified into three subfamilies. Phylogenetic analysis showed that the CsYUC gene family is evolutionarily conserved. The physical and chemical properties, gene structures, and conserved domains were analyzed. The expression profiles of CsYUCs were analyzed on the basis of open available RNA-seq data, as well as by RNA-seq and qRT-PCR assays. Combined with previous studies, it can be concluded that YUC10 may play key roles in seed development. The results also showed that CsYUC2.1 may play important roles in the coordinated regulation of the growth of leaf buds and flower buds induced by pruning. Low temperature markedly induced the expression of CsYUC2.2, -11.8, and -11.9. Furthermore, CsYUC genes that might play key roles in the specific development stages and involve enhancing the resistance to drought and NaCl stress were screened, respectively. This study could provide a research basis for deeply studying the gene functions of the CsYUC family in the tea plant. Full article

Panicle development and grain production in crop species are essential breeding characteristics affected by the synthesis of auxin, which is influenced by flavin monooxygenase-encoding genes such as YUC (YUCCA) family members. In this trial, fourteen YUCs were identified and named uniformly in foxtail millet, an ancient crop species cultivated across the world. The phylogenetic analysis revealed that the SiYUCs were clustered into four subgroups; protein motif and gene structure analyses suggested that the closely clustered SiYUC genes were relatively conserved within each subgroup; while genome mapping analysis indicated that the SiYUC genes were unevenly distributed on foxtail millet chromosomes and colinear with other grass species. Transcription analysis revealed that the SiYUC genes differed greatly in expression pattern in different tissues and contained hormonal/light/stress-responding cis-elements. The haplotype characterization of SiYUC genes indicated many superior haplotypes of SiYUCs correlated with higher panicle and grain weight could be favorably selected by breeding. These results will be useful for the further study of the functional characteristics of SiYUC genes, particularly with regard to the marker-assisted pyramiding of beneficial haplotypes in foxtail millet breeding programs. Full article