Abscisic Acid Signaling Pathway Research Articles

Wheat TaPYL9-involved signalling pathway impacts plant drought response through regulating distinct osmotic stress-associated physiological indices.

The abscisic acid (ABA) signalling pathway plays a crucial role in plants' response to drought stress. In this study, we aimed to characterize the impact of an ABA signalling module, which consisted of TaPYL9 and its downstream partners in Triticum aestivum, on plant drought adaptation. Our results showed that TaPYL9 protein contains conserved motifs and targets plasma membrane and nucleus after being sorted by the endoplasmic reticulum. In addition, TaPYL9 transcripts in both roots and leaves were significantly upregulated in response to drought stress. We conducted glucuronidase (GUS) histochemical staining analysis for transgenic plants carrying a truncated TaPYL9 promoter, which suggested that cis-elements associate with ABA and drought response, such as ABRE, DRE and recognition sites MYB and MYC, regulating the gene transcription under drought conditions. Using protein interaction assays (i.e., yeast two-hybrid, bimolecular fluorescence complementation (BiFC), co-immunoprecipitation (Co-IP) and in vitro pull-down), we demonstrated interactions between the intermediate segment of TaPYL9, the intermediate segment of TaPP2C6, the N-terminus of TaSnRK2.8 and the C-terminus of the transcription factor TabZIP1 in wheat, indicating the involvement of TaPYL9 in the constitution of an ABA signalling module, namely TaPYL9/TaPP2C6/TaSnRK2.8/TabZIP1. Transgene analysis revealed that TaPYL9, TaSnRK2.8 and TabZIP1 positively regulated drought response, while TaPP2C6 negatively regulated it, and that these genes were closely associated with the regulation of stomata movement, osmolyte accumulation and ROS homeostasis. Electrophoretic mobility shift (EMSA) and transcriptioal activation assays indicated that TabZIP1 interacted promoters of TaP5CS2, TaSLAC1-1 and TaCAT2 and activated transcription of these genes, which regulated proline biosynthesis, stomata movement and ROS scavenging upon drought signalling, respectively. Furthermore, we found that the transcripts of TaPYL9 and stress-responsive genes were positively correlated with yields in wheat cultivars under field drought conditions. Altogether, our findings suggest that the TaPYL9-involved signalling pathway significantly regulates drought response by modulating osmotic stress-associated physiological processes in T. aestivum.

A pearl millet plasma membrane protein, PgPM19, facilitates seed germination through the negative regulation of abscisic acid-associated genes under salinity stress in Arabidopsis thaliana.

The pearl millet gene PgPM19 inhibits seed dormancy by negatively regulating the ABA biosynthesis and ABA signaling pathways in response to salinity stress in Arabidopsis. Abscisic acid (ABA) plays a pivotal role in orchestrating plant stress responses and development. However, how the ABA signal is transmitted in response to stresses remains primarily uncertain, particularly in monocotyledonous plants. In this study, PgPM19, a gene whose expression is induced by drought, salinity, heat, and ABA in both leaf and root tissues, was isolated from pearl millet. The expression of PgPM19 in yeast cells did not influence their growth when subjected to mannitol, sorbitol, or NaCl stress. However, Arabidopsis plants overexpressing PgPM19 (PgPM19_OE plants) exhibited increased germination rates, greater fresh weights and longer roots under salinity stress during germination, compared to wild-type (WT) plants. Conversely, the pm19L1 (SALK_075435) mutant, featuring a transfer DNA insertion in a closely related PgPM19 homolog (AT1G04560) in Arabidopsis, demonstrated reduced germination rates and smaller fresh weights under salinity-stressed condition than did WT and PgPM19_OE plants. A pivotal ABA biosynthesis gene, NCED3, ABA signaling pathway genes, such as PYL6 and SnRK2.7, alongside downstream ABI genes and stress-responsive genes RAB28 and RD29, were downregulated in PgPM19_OE plants, as evidenced by both transcriptome analysis and quantitative reverse transcription-PCR. These findings raise the possibility that PgPM19 is involved in regulating seed germination by mediating ABA biosynthesis and signaling pathway in response to salinity stress in Arabidopsis. This study contributes to a better understanding of PgPM19 in response to salinity stress and establishes a foundation for unraveling the crosstalk of stress responses and ABA in Arabidopsis and other plant species.

Ubiquitin-Specific Protease 15 Plays an Important Role in Controlling the Tolerance to Salt, Drought and Abscisic Acid in Arabidopsis thaliana

Ubiquitin-specific proteases (UBPs), the largest subfamily of deubiquitinating enzymes (DUBs), are critical for plant growth and development as well as abiotic-stress responses. In this study, we discovered that the expression of the ubiquitin-specific protease 15 (UBP15) gene of the gene ubiquitin-specific protease 15 (UBP15) was induced by salt, mannitol and abscisic acid (ABA) treatments. Further research revealed that UBP15 is involved in modulation of salt, drought tolerance and ABA signaling during seed germination, early seedling development, post-germination root growth or adult-plant stage. Enrichment analysis showed that many genes related to abiotic stresses and metabolic pathways were altered in the ubp15-1 mutant. Through the joint analysis of the quantitative real-time polymerase chain reaction (qRT-PCR) and differentially-expressed gene relationship network, we found that UBP15 may mainly regulate salt-stress tolerance by modulating the dwarf and delayed flowering 1 (DDF1) pathway through a cascade reaction. In the regulation of drought-stress responses, ring domain ligase1 (RGLG1) may be a direct substrate of UBP15. Moreover, we cannot exclude the possibility that UBP15 acts in a feed-forward loop mechanism in the regulation of drought-stress responses via ethylene response factor 53 (ERF53) and its ubiquitin (Ub) ligase RGLG1. In ABA signal transduction, UBP15 may play a role in at least three aspects of the ABA signaling pathway: ABA synthesis, stomatal closure regulated by ABA signaling, and transcription factors in the ABA pathway. Taken together, our results suggest that UBP15 is involved in salt, osmotic, and drought-stress tolerance and the ABA signaling pathway by directly regulating the stability of key substrates or indirectly affecting the expression of genes related to abiotic stresses in Arabidopsis thaliana. Our research provides new germplasm resources for stress-resistant crops cultivation. These results demonstrate that UBP15 is a key regulator of salt, drought and ABA tolerance in Arabidopsis.

The transcription factor TaFDL2-1A functions in auxin metabolism mediated by abscisic acid to regulate shoot growth in wheat.

Genetic strategies can be effective in improving wheat (Triticum aestivum L.) drought stress tolerance, but accumulating evidence suggests that overexpressing drought-resistance genes, especially genes related to the abscisic acid (ABA) signaling pathway, can retard plant growth. We previously characterized the positive roles of the wheat bZIP transcription factor TaFD-Like2-1A (TaFDL2-1A) in drought stress tolerance and ABA biosynthesis and response, whereas a dwarfing shoot exhibited under normal conditions. This study determined the underlying mechanisms that allow TaFDL2-1A to affect shoot growth. Overexpressing TaFDL2-1A decreased cell length, cell width, leaf size, shoot length, and biomass in wheat. The results of RNA-seq showed that multiple differently expressed transcripts are enriched in the auxin signaling pathway. Further analysis indicated higher expression levels of Gretchen Hagen3 (GH3) genes and lower indole-3-acetic acid (IAA) concentrations in the TaFDL2-1A overexpression lines. Exogenous IAA treatment restored the phenotypes of the TaFDL2-1A overexpression lines to wild-type levels. Transcriptional regulation analysis suggested that TaFDL2-1A enhances the expression of auxin metabolism genes, such as TaGH3.2-3A, TaGH3.2-3B, TaGH3.8-2A, and TaGH3.8-2D, by directly binding to ACGT core cis-elements. Furthermore, tafdl2 knock-out plants had lower expression levels of these GH3 genes and higher IAA levels than Fielder wheat. These GH3 gene expression and IAA levels were induced and reduced in Fielder wheat and tafdl2 knock-out plants treated with exogenous ABA. Our findings elucidate mechanisms underlying the functional redundancy of TaFDL2-1A in the crosstalk between ABA and IAA to affect shoot growth and provide insights into the balance between drought resistance and yield in wheat.

OsPP2C49, a Negative Regulatory Factor in the Abscisic Acid Signaling Pathway, Positively Regulates Grain Yield in Rice

Clade A type 2C protein phosphatases (PP2Cs) are crucial components of the abscisic acid (ABA) signaling pathway. Research on clade A PP2Cs has focused more on their roles related to ABA signaling and stress responses than on the molecular mechanisms mediating their effects on plant growth and grain yield. Rice (Oryza sativa L.) is an important food crop worldwide. We previously determined that OsPP2C49, which encodes a rice clade A PP2C family member, negatively controls rice responses to drought, salt, and high-temperature stresses. In this study, we investigated the regulatory effects of OsPP2C49 on ABA responses and rice grain yield. By analyzing potential interactions with core ABA components, including pyrabactin resistance 1 (PYR1)/PYR1-like (PYL)/regulatory component of the ABA receptor (RCAR) and stress-activated protein kinases (SAPKs), we confirmed that OsPP2C49 is involved in the ABA signaling pathway. OsPP2C49 overexpression led to decreased ABA sensitivity and increased rice grain yield; the opposite phenotypes were observed in the ospp2c49 knockout mutants. Therefore, OsPP2C49 negatively regulates ABA responses, but positively modulates rice grain yield. Furthermore, we found that OsPP2C49 can interact with and dephosphorylate five OsSAPKs in vitro. Unlike OsPP2C49, these OsSAPKs positively modulate ABA responsiveness, but negatively affect rice yield. These findings indicate that OsPP2C49 may partially regulate ABA responses and rice grain production by dephosphorylating OsSAPKs. This study preliminarily explored the molecular basis of the regulatory effects of OsPP2C49 on rice plant growth and grain yield.

A Positive Role for CaMEKK17 in Response to Drought Stress, Modulated by Clade A PP2Cs.

The abscisic acid (ABA) signaling pathway is essential for plant response to abiotic stresses and can be modulated positively or negatively by MAPKKK proteins. This study focuses on the functional characterization of CaMEKK17, a MAPKKK previously recognized for its rapid induction under drought stress. Functional analyses demonstrated that CaMEKK17 is an active serine/threonine kinase with a conserved catalytic domain that is crucial for its kinase activity. CaMEKK17 silencing in pepper plants resulted in reduced drought tolerance, characterized by increased transpirational water loss and impaired ABA-mediated stomatal closure. Conversely, CaMEKK17 overexpression in Arabidopsis increased kinase activity, enhancing ABA sensitivity and drought tolerance. Further investigation revealed that CaMEKK17 interacts with pepper group A type 2C protein phosphatases (PP2Cs), particularly CaAITP1 and CaAIPP1, which inhibit its kinase activity. Protein-protein interactions mediated inhibition by CaAITP1, whereas CaAIPP1 relied on its phosphatase activity. Double gene silencing of CaMEKK17 and CaAITP1 demonstrated that CaMEKK17 functions downstream of CaAITP1 in ABA-mediated drought tolerance. Taken together, our findings suggest that CaMEKK17 positively modulates drought tolerance in pepper plants but may be inhibited by PP2Cs.

Development and drought escape response in Arabidopsis thaliana are regulated by AtPLC1 in response to abscisic acid.

AtPLC1 plays a critical role in plant growth, development, and response to drought stress. Phosphoinositide-specific phospholipase C (PI-PLC) hydrolyzes substrates to generate secondary messengers crucial for plant growth, development, and stress responses. Drought escape (DE) response is an adaptive strategy that plants employ under drought conditions. The expression levels of the flower meristem-specific gene APETALA 1 and flowering regulatory genes FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 were downregulated in plc1, and FLOWERING LOCUS C was upregulated. The flowering time of the plc1flc double mutant was earlier than that of the wild type. Transcriptome analysis revealed that the Gene Ontology of differentially expressed genes (DEGs) was enriched in abscisic acid (ABA) response signaling, and Kyoto Encyclopedia of Genes and Genomes analysis revealed differential gene expression annotated to plant hormone signaling pathways. Our experiments show that AtPLC1 is upregulated by ABA in Arabidopsis. Under ABA induction and water stress, wild-type plants exhibit a DE response, and the DE response in plc1 disappears. Expression levels of ABA signaling pathway transcription factors ABA-responsive element-binding factors 3 (ABF3) and ABF4 were downregulated in plc1. In conclusion, our study suggests that AtPLC1 participates in regulating plant growth and development and participates in the DE response through the regulation of ABA signaling pathway transcription factors ABF3/ABF4. The study enhances our comprehension of the role of AtPLC1 in plant development and drought stress, providing a theoretical foundation for further investigation into DE responses.

Transcription Factor OsMYB2 Triggers Amino Acid Transporter OsANT1 expression to Regulate Rice Growth and Salt Tolerance.

Amino acid transporters play important roles in plant growth and stress tolerance; however, whether the abscisic acid signaling pathway regulates their transcription in rice (Oryza sativa) under salt stress remains unclear. In this study, we report that the transcription factor OsMYB2 (MYB transcription factor 2) of the abscisic acid signaling pathway mediates the expression of the gene encoding the amino acid transporter OsANT1 (aromatic and neutral amino acid transporter 1), which positively regulates growth and salt tolerance in rice. OsANT1 was mainly expressed in the leaf blade and panicle under normal conditions and transports leucine, phenylalanine, tyrosine and proline, positively regulating tillering and yield in rice. Nevertheless, salt stress induced the accumulation of abscisic acid and strongly increased the expression level of OsANT1 in the root, resulting in enhanced salt tolerance of rice seedlings, as evidenced by higher proline concentration and antioxidant-like enzyme activities and lower malondialdehyde and hydrogen peroxide concentrations. Moreover, we showed that OsMYB2 interacts with the promoter of OsANT1 and promotes its expression. Overexpression of OsMYB2 also improved tillering, yield, and salt tolerance in rice. In conclusion, our results suggest that the transcription factor OsMYB2 triggers OsANT1 expression and regulates growth and salt tolerance in rice, providing insights into the role of the abscisic acid signaling pathway in the regulatory mechanism of amino acid transporters in response to salt stress.

The ubiquitin E3 ligase RZFP1 affects drought tolerance in poplar by mediating the degradation of the protein phosphatase PP2C-9.

Abscisic acid signaling has been implicated in plant responses to water deficit-induced osmotic stress. However, the underlying molecular mechanism remains unelucidated. This study identified the RING-type E3 ubiquitin ligase RING ZINC FINGER PROTEIN1 (PtrRZFP1) in poplar (Populus trichocarpa), a woody model plant. PtrRZFP1 encodes a ubiquitin E3 ligase that participates in protein ubiquitination. PtrRZFP1 mainly functions in the nucleus and endoplasmic reticulum and is activated by drought and abscisic acid. PtrRZFP1-overexpressing transgenic poplars (35S:PtrRZFP1) showed greater tolerance to drought, whereas PtrRZFP1-knockdown lines (KD-PtrRZFP1) showed greater sensitivity to drought. Under treatment with polyethylene glycol and abscisic acid, PtrRZFP1 promoted the production of NO and H2O2 in stomatal guard cells, ultimately enhancing stomatal closure and improving drought tolerance. Additionally, PtrRZFP1 physically interacted with the clade A Protein Phosphatase 2C protein PtrPP2C-9, a core regulator of abscisic acid signaling, and mediated its ubiquitination and eventual degradation through the ubiquitination-26S proteasome system, indicating that PtrRZFP1 positively regulates the abscisic acid signaling pathway. Furthermore, the PtrPP2C-9-overexpression line was insensitive to abscisic acid and more sensitive to drought than the wild-type plants, whereas the opposite phenotype was observed in 35S:PtrRZFP1 plants. In general, PtrRZFP1 negatively regulates the stability of PtrPP2C-9 to mediate poplar drought tolerance. The results of this study provide a theoretical framework for the targeted breeding of drought-tolerant traits in perennial woody plants.

Biosynthesis and Signaling of Strigolactones Act Synergistically With That of ABA and JA to Enhance Verticillium dahliae Resistance in Cotton (Gossypium hirsutum L.).

Verticillium wilt (VW) caused by the soil-borne fungal pathogen Verticillium dahliae reduces cotton productivity and quality. Numerous studies have explored the genetic and molecular mechanisms regulating VW resistance in cotton, but the role and mechanism of strigolactone (SL) is still elusive. We investigated the function of SL in cotton's immune response to V. dahliae infection by exogenously applying SL analog, blocking or enhancing biosynthesis of endogenous SLs in combination with comparative transcriptome analysis and by exploring cross-talk between SL and other phytohormones. Silencing GhDWARF27 and applying the SL analog GR24 or overexpressing GhDWARF27 decreased and enhanced V. dahliae resistance, respectively. Transcriptome analysis revealed SL-mediated activation of abscisic acid (ABA) and jasmonic acid (JA) biosynthesis and signaling pathways. Enhanced ABA biosynthesis and signaling led to increased activity of antioxidant enzymes and reduced buildup of excess reactive oxygen species. Enhanced JA biosynthesis and signaling facilitated transcription of JA-dependent disease resistance genes. One of the components of the SL signal transduction pathway, GhD53, was found to interact with GhNCED5 and GhLOX2, the key enzymes of ABA and JA biosynthesis, respectively. We revealed the molecular mechanism underlying SL-enabled V. dahliae resistance and provided potential solutions for improving VW resistance in cotton.

Identification of VvAGL Genes Reveals Their Network's Involvement in the Modulation of Seed Abortion via Responding Multi-Hormone Signals in Grapevines.

The formation of seedless traits is regulated by multiple factors. AGLs, which belong to the MADS-box family, were reported to be important regulators in this process; however, the underlying mechanism remains elusive. Here, we identified the VvAGL sub-family genes during the seed abortion process in seedless grapevine cv. 'JingkeJing' and found 40 differentially expressed VvAGL members and 1069 interacting proteins in this process. Interestingly, almost all members and their interacting proteins involved in the tryptophan metabolic pathway (K14486) and participated in the phytohormone signalling (KO04075) pathway, including the growth hormone (IAA), salicylic acid (SA), abscisic acid (ABA), cytokinin (CTK), and ethylene signalling pathways. The promoters of AGL sub-family genes contain cis-elements in response to hormones such as IAA, ABA, CTK, SA, and ETH, implying that they might respond to multi-hormone signals and involve in hormone signal transductions. Further expression analysis revealed VvAGL6-2, VvAGL11, VvAGL62-11, and VvAGL15 had the highest expression at the critical period of seed abortion, and there were positive correlations between ETH-VvAGL15-VvAGL6-2, ABA-VvAGL80, and SA-VvAGL62 in promoting seed abortion but negative feedback between IAA-VvAGL15-VvAGL6-2 and CTK-VvAGL11. Furthermore, many genes in the IAA, ABA, SA, CTK, and ETH pathways had a special expressional pattern in the seed, whereby we developed a regulatory network mediated by VvAGLs by responding to multihormonal crosstalk during grape seed abortion. Our findings provide new insights into the regulatory network of VvAGLs in multi-hormone signalling to regulate grape seed abortion, which could be helpful in the molecular breeding of high-quality seedless grapes.

Comparative physiological and transcriptomic analyses reveal genotype specific response to drought stress in Siberian wildrye (Elymus sibiricus)

Siberian wildrye (Elymus sibiricus) is a xero-mesophytic forage grass with high nutritional quality and stress tolerance. Among its numerous germplasm resources, some possess superior drought resistance. In this study, we firstly investigated the physiological differences between the leaves of drought-tolerant (DT) and drought-sensitive (DS) genotypes under different field water contents (FWC) in soil culture. The results showed that, under drought stress, DT maintained a lower leaf water potential for water absorption, sustained higher photosynthetic efficiency, and reduced oxidative damage in leaves by efficiently maintaining the ascorbic acid-glutathione (ASA-GSH) cycle to scavenge reactive oxygen species (ROS) compared to DS. Secondly, using RNA sequencing (RNA-seq), we analyzed the gene expression profiles of DT and DS leaves under osmotic stress of hydroponics induced by PEG-6000. Through differential analysis, we identified 1226 candidate unigenes, from which we subsequently screened out 115/212 differentially expressed genes (DEGs) that were more quickly induced/reduced in DT than in DS under osmotic stress. Among them, Unigene0005863 (EsSnRK2), Unigene0053902 (EsLRK10) and Unigene0031985 (EsCIPK5) may be involved in stomatal closure induced by abscisic acid (ABA) signaling pathway. Unigene0047636 (EsCER1) may positively regulates the synthesis of very-long-chain (VLC) alkanes in cuticular wax biosynthesis, influencing plant responses to abiotic stresses. Finally, the contents of wax and cutin were measured by GC–MS under osmotic stress of hydroponics induced by PEG-6000. Corresponding to RNA-seq, contents of wax monomers, especially alkanes and alcohols, showed significant induction by osmotic stress in DT but not in DS. It is suggested that limiting stomatal and cuticle transpiration under drought stress to maintain higher photosynthetic efficiency and water use efficiency (WUE) is one of the critical mechanisms that confer stronger drought resistance to DT. This study provides some insights into the molecular mechanisms underlying drought tolerance in E. sibiricus. The identified genes may provide a foundation for the selection and breeding of drought-tolerant crops.

Analysis of expression characteristics and identification of interaction proteins of transcription factor BnaABI5 in Brassica napus.

Rapeseed is one important oil crop in China. However, its planting benefit is frequently affected by environmental stresses such as drought in the northwest region of China. The abscisic acid(ABA) signaling pathway plays an important role in plant abiotic stress response and tolerance, and ABFs/AREBs(ABA-responsive element binding factors/ABA-responsive element binding proteins) are the core transcription factors that regulate the expression of ABA-responsive genes. To dissect the key transcription factors mediated abiotic stress, we mainly characterized abscisic acid insensitive 5(BnaABI5) in rapeseed, including its subcellular localization, expression pattern in response to various stress and tissue-specific expression analysis, transcriptional activity analysis as well as interaction screening with BnaMPKs(mitogen-activated protein kinases). Our results showed that the BnaABI5-GFP fusion protein was localized in the nucleus, and its transcript level is induced by drought stress and was mainly expressed in the roots of rapeseed. Furthermore, BnaABI5 showed transcriptional activation activity through a yeast transactivation assay and it also activated the promoter activity of EM6 target gene in the transient expression system in tobacco leaves. Moreover, BnaABI5 interacted with BnaMPK6 and BnaMPK13 through BiFC and Y2H analysis. This study preliminarily explored the expression characteristics of transcription factor BnaABI5 and its interaction with BnaMPKs, which might help us for further understanding the function of BnaABI5.

Genome-wide analysis of HD-Zip genes in Sophora alopecuroides and their role in salt stress response.

We aimed to identify HD-Zip (homologous domain leucine zipper) family genes based on the complete Sophora alopecuroides genome sequence. Eighty-six Sophora alopecuroides HD-Zip family (SaHDZ) genes were identified and categorized into four subclasses using phylogenetic analysis. Chromosome localization analysis revealed that these genes were distributed across 18 chromosomes. Gene structure and conserved motif analysis showed high similarity among members of the SaHDZ genes. Prediction analysis revealed 71 cis-acting elements in SaHDZ genes. Transcriptome and quantitative real-time polymerase chain reaction analyses showed that under salt stress, SaHDZ responded positively in S. alopecuroides, and that SaHDZ22 was significantly upregulated afterward. Functional verification experiments revealed that SaHDZ22 overexpression increased the tolerance of Arabidopsis to salt and osmotic stress. Combined with cis-acting element prediction and expression level analysis, HD-Zip family transcription factors may be involved in regulating the balance between plant growth and stress resistance under salt stress by modulating the expression of auxin and abscisic acid signaling pathway genes. The Sophora alopecuroides adenylate kinase protein (SaAKI) and S. alopecuroides tetrapeptide-like repeat protein (SaTPR; pCAMBIA1300-SaTPR-cLUC) expression levels were consistent with those of SaHDZ22, indicating that SaHDZ22 may coordinate with SaAKI and SaTPR to regulate plant salt tolerance. These results lay a foundation in understanding the salt stress response mechanisms of S. alopecuroides and provide a reference for future studies oriented toward exploring plant stress resistance.

Integrative physiology and transcriptome sequencing reveal differences between G. hirsutum and G. barbadense in response to salt stress and the identification of key salt tolerance genes

BackgroundSoil salinity is one of the major abiotic stresses that threatens crop growth. Cotton has some degree of salt tolerance, known as the “pioneer crop” of saline-alkali land. Cultivation of cotton is of great significance to the utilization of saline-alkali land and the development of cotton industry. Gossypium hirsutum and G. barbadense, as two major cotton species, are widely cultivated worldwide. However, until recently, the regulatory mechanisms and specific differences of their responses to salt stress have rarely been reported.ResultsIn this study, we comprehensively compared the differences in the responses of G. hirsutum acc. TM-1 and G. barbadense cv. Hai7124 to salt stress. The results showed that Hai7124 exhibited better growth than did TM-1 under salt stress, with greater PRO content and antioxidant capability, whereas TM-1 only presented greater K+ content. Transcriptome analysis revealed significant molecular differences between the two cotton species in response to salt stress. The key pathways of TM-1 induced by salt are mainly related to growth and development, such as porphyrin metabolism, DNA replication, ribosome and photosynthesis. Conversely, the key pathways of Hai7124, such as plant hormone signal transduction, MAPK signaling pathway-plant, and phenylpropanoid biosynthesis, are mainly related to plant defense. Further comparative analyses of differentially expressed genes (DEGs) revealed that antioxidant metabolism, abscisic acid (ABA) and jasmonic acid (JA) signalling pathways were more strongly activated in Hai7124, whereas TM-1 was more active in K+ transporter-related genes and ethylene (ETH) signalling pathway. These differences underscore the various molecular strategies adopted by the two cotton species to navigate through salt stress, and Hai7124 responded more strongly to salt stress, which explains the potential reasons for the greater salt tolerance of Hai7124. Finally, we identified 217 potential salt tolerance-related genes, 167 of which overlapped with the confidence intervals of significant SNPs identified in previous genome-wide association studies (GWASs), indicating the high reliability of these genes.ConclusionsThese findings provide new insights into the differences in the regulatory mechanisms of salt tolerance between G. hirsutum and G. barbadense, and identify key candidate genes for salt tolerance molecular breeding in cotton.

A significant correlation between ABA-induced seed-germination delay and salt tolerance of seedling in Brassica napus

ABSTRACT Under abiotic stresses, such as salt stress, abscisic acid (ABA) production is induced and enhances stress tolerance. ABA is also an important plant hormone that regulates vital biological responses, including seed gemination delay. However, the interplay between stress conditions and biological responses is not well understood. Previously, we reported a wide salt tolerance variation among Brassica napus varieties. This range of salt tolerance makes B. napus ideal for exploring the relationship between salt tolerance and ABA-induced seed germination delay. First, we investigated the ABA-induced seed-germination delay of 22 B. napus varieties, each with different salt tolerances. We observed that highly salt-tolerant varieties exhibited significant seed-germination delays when exposed to increasing ABA concentrations. Additionally, among the varieties, exogenous ABA induced a range of different germination delays, suggesting a significant correlation between germination delay and salt tolerance at the seedling stage. Expression analysis, with and without ABA treatment, for several genes involved in the ABA signalling pathway and downstream was also performed at seed germination. The results suggest the potential involvement of ABI5 and SOS1 in both germination regulation and salt tolerance.

Arabidopsis Histone Variant H2A.X Functions in the DNA Damage-Coupling Abscisic Acid Signaling Pathway.

Environmental variations initiate chromatin modifications, leading to the exchange of histone subunits or the repositioning of nucleosomes. The phosphorylated histone variant H2A.X (γH2A.X) is recognized for the formation of foci that serve as established markers of DNA double-strand breaks (DSBs). Nevertheless, the precise roles of H2A.X in the cellular response to genotoxic stress and the impact of the plant hormone abscisic acid (ABA) remain incompletely understood. In this investigation, we implemented CRISPR/Cas9 technology to produce loss-of-function mutants of AtHTA3 and AtHTA5 in Arabidopsis. The phenotypes of the athta3 and athta5 single mutants were nearly identical to those of the wild-type Col-0. Nevertheless, the athta3 athta5 double mutants exhibited aberrant embryonic development, increased sensitivity to DNA damage, and higher sensitivity to ABA. The RT-qPCR analysis indicates that AtHTA3 and AtHTA5 negatively regulate the expression of AtABI3, a fundamental regulator in the ABA signaling pathway. Subsequent investigation demonstrated that AtABI3 participates in the genotoxic stress response by influencing the expression of DNA damage response genes, such as AtBRCA1, AtRAD51, and AtWEE1. Our research offers new insights into the role of H2A.X in the genotoxic and ABA responses of Arabidopsis.

Protein kinase MeSnRK2.3 positively regulates starch biosynthesis by interacting with the transcription factor MebHLH68 in cassava.

Starch biosynthesis involves numerous enzymes and is a crucial metabolic activity in plant storage organs. Sucrose non-fermenting related protein kinase 2 (SnRK2) is an abscisic acid (ABA)-dependent kinase and a significant regulatory enzyme in the ABA signaling pathway. However, whether SnRK2 kinases regulate starch biosynthesis is unclear. In this study, we identified that MeSnRK2.3, an ABA-dependent kinase, was highly expressed in the storage roots of cassava and was induced by ABA. Overexpression of MeSnRK2.3 in cassava significantly increased the starch content in the storage roots and promoted plant growth. MeSnRK2.3 was further found to interact with the cassava basic helix-loop-helix 68 (MebHLH68) transcription factor in vivo and in vitro. MebHLH68 directly bound to the promoters of sucrose synthase 1 (MeSUS1), granule-bound starch synthase I a (MeGBSSIa), and starch-branching enzyme 2.4 (MeSBE2.4), thereby upregulating their transcriptional activities. Additionally, MebHLH68 negatively regulated the transcriptional activity of sucrose phosphate synthase B (MeSPSB). Moreover, phosphorylated MebHLH68 by MeSnRK2.3 up-regulated the transcription activity of MeSBE2.4. These findings demonstrated that the MeSnRK2.3-MebHLH68 module connects the ABA signaling pathway and starch biosynthesis in cassava, thereby providing direct evidence of ABA-mediated participation in the sucrose metabolism and starch biosynthesis pathway.

Crosstalk between Ethylene, Jasmonate and ABA in Response to Salt Stress during Germination and Early Plant Growth in Cucurbita pepo.

The crosstalk of phytohormones in the regulation of growth and development and the response of plants to environmental stresses is a cutting-edge research topic, especially in crop species. In this paper, we study the role and crosstalk between abscisic acid (ABA), ethylene (ET), and jasmonate (JA) in the control of germination and seedling growth in water or in standard nutrient solution and under salt stress (supplemented with 100-200 mM NaCl). The roles of ET and JA were studied using squash ET- and JA-deficient mutants aco1a and lox3a, respectively, while the crosstalk between ET, JA, and ABA was determined by comparing the expression of the key ABA, JA, and ET genes in wild-type (WT) and mutant genotypes under standard conditions and salt stress. Data showed that ET and JA are positive regulators of squash germination, a function that was found to be mediated by downregulating the ABA biosynthesis and signaling pathways. Under salt stress, aco1a germinated earlier than WT, while lox3a showed the same germination rate as WT, indicating that ET, but not JA, restricts squash germination under unfavorable salinity conditions, a function that was also mediated by upregulation of ABA. ET and JA were found to be negative regulators of plant growth during seedling establishment, although ET inhibits both the aerial part and the root, while JA inhibits only the root. Both aco1a and lox3a mutant roots showed increased tolerance to salt stress, a phenotype that was found to be mainly mediated by JA, although we cannot exclude that it is also mediated by ABA.

The Concerted Function of a Novel Class of Transcription Factors, ZBFs, in Light, Jasmonate and Abscisic Acid Signaling Pathways.

Several classes of transcription factors have been investigated in light signaling pathways that bind to the Light Responsive Elements (LREs) present in the promoters of light regulatory genes for transcriptional regulation. Some of these transcription factors have been shown to be binding to numerous promoters through genome-wide ChIP-on-chip (ChIP-chip) studies. Furthermore, through the integration of ChIP-seq and RNA-seq techniques, it has been demonstrated that a transcription factor modifies the expression of numerous genes with which it interacts. However, the mode of action of these transcription factors and their dependency on other regulators in the pathway has just started to be unraveled. In this review article, we focus on a particular class of transcription factors, ZBF (Z-box Binding Factor), and their associated partners within the same or other classes of transcription factors and regulatory proteins during photomorphogenesis. Moreover, we have further made an attempt to summarize the cross talk of these transcription factors with jasmonic acid, abscisic acid and salicylic acid mediated defense signaling pathways. This review offers an in-depth insight into the manner in which ZBFs and their interactors reshape cellular functions and plant behavior. The underlying principles not only contribute to a comprehensive understanding but also establish a framework for analyzing the interplay between early developmental events and hormone signaling, a regulation orchestrated by the ZBF family.