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Several nucleoporins in the nuclear pore complex (NPC) have been reported to be involved in abiotic stress responses in plants. However, the molecular mechanism of how NPC regulates abiotic stress responses, especially the expression of stress responsive genes remains poorly understood. From a forward genetics screen using an abiotic stress-responsive luciferase reporter (RD29A-LUC) in the sickle-1 (sic-1) mutant background, we identified a suppressor caused by a mutation in NUCLEOPORIN 85 (NUP85), which exhibited reduced expression of RD29A-LUC in response to ABA and salt stress. Consistently, the ABA and salinity induced expression of several stress responsive genes such as RD29A, COR15A and COR47 was significantly compromised in nup85 mutants and other nucleoporin mutants such as nup160 and hos1. Subsequently, Immunoprecipitation and mass spectrometry analysis revealed that NUP85 is potentially associated with HOS1 and other nucleoporins within the nup107-160 complex, along with several mediator subunits. We further showed that there is a direct physical interaction between MED18 and NUP85. Similar to NUP85 mutations, MED18 mutation was also found to attenuate expression of stress responsive genes. Taken together, we not only revealed the involvement of NUP85 and other nucleoporins in regulating ABA and salt stress responses, but also uncovered a potential relation between NPC and mediator complex in modulating the gene expression in plants. [ABSTRACT FROM AUTHOR]

The phytohormone abscisic acid (ABA) regulates plant growth, development and responses to biotic and abiotic stresses. The core ABA signaling pathway consists of three major components: ABA receptor (PYR1/PYLs), type 2C Protein Phosphatase (PP2C) and F1-elated protein inase 2 (SnRK2). Nevertheless, the complexity of ABA signaling remains to be explored. To uncover new components of ABA signal transduction pathways, we performed a yeast two-hybrid screen for SnRK2-interacting proteins. We found that ype ne rotein hosphatase 1 (TOPP1) and its regulatory protein, nhibitor-2 (AtI-2), physically interact with SnRK2s and also with PYLs. TOPP1 inhibited the kinase activity of SnRK2.6, and this inhibition could be enhanced by AtI-2. Transactivation assays showed that TOPP1 and AtI-2 negatively regulated the SnRK2.2/3/6-mediated activation of the ABA responsive reporter gene RD29B, supporting a negative role of TOPP1 and AtI-2 in ABA signaling. Consistent with these findings, topp1 and ati-2 mutant plants displayed hypersensitivities to ABA and salt treatments, and transcriptome analysis of TOPP1 and AtI-2 knockout plants revealed an increased expression of multiple ABA-responsive genes in the mutants. Taken together, our results uncover TOPP1 and AtI-2 as negative regulators of ABA signaling. [ABSTRACT FROM AUTHOR]

Summary: The control of flowering time in maize is crucial for reproductive success and yield, and it can be influenced by environmental stresses. Using the approaches of Ac/Ds transposon and transposable element amplicon sequencing techniques, we identified a Ds insertion mutant in the ZmPRR37 gene. The Ds insertion showed a significant correlation with days to anthesis. Further research indicated that ZmPRR37‐CR knockout mutants exhibited early flowering, whereas ZmPRR37‐overexpression lines displayed delayed flowering compared to WT under long‐day (LD) conditions. We demonstrated that ZmPRR37 repressed the expression of ZmNF‐YC2 and ZmNF‐YA3 to delay flowering. Association analysis revealed a significant correlation between flowering time and a SNP2071‐C/T located upstream of ZmPRR37. The SNP2071‐C/T impacted the binding capacity of ZmELF6 to the promoter of ZmPRR37. ZmELF6 also acted as a flowering suppressor in maize under LD conditions. Notably, our study unveiled that ZmPRR37 can enhance salt stress tolerance in maize by directly regulating the expression of ABA‐responsive gene ZmDhn1. ZmDhn1 negatively regulated maize salt stress resistance. In summary, our findings proposed a novel pathway for regulating photoperiodic flowering and responding to salt stress based on ZmPRR37 in maize, providing novel insights into the integration of abiotic stress signals into floral pathways. [ABSTRACT FROM AUTHOR]

Drought stress adversely impacts crop development and yield. Maize frequently encounters drought stress during its life cycle. Improvement of drought tolerance is a priority of maize breeding programs. Here, we identified a novel transcription factor encoding gene, APETALA2 (AP2)/Ethylene response factor (ERF), which is tightly associated with drought tolerance in maize seedlings. ZmERF21 is mainly expressed in the root and leaf and it can be highly induced by polyethylene glycol treatment. Genetic analysis showed that the zmerf21 mutant plants displayed a reduced drought tolerance phenotype, accompanied by phenotypical and physiological changes that are commonly observed in drought conditions. Overexpression of ZmERF21 in maize significantly increased the chlorophyll content and activities of antioxidant enzymes under drought conditions. RNA‐Seq and DNA affinity purification sequencing analysis further revealed that ZmERF21 may directly regulate the expression of genes related to hormone (ethylene, abscisic acid) and Ca signaling as well as other stress‐response genes through binding to the promoters of potential target genes. Our results thereby provided molecular evidence of ZmERF21 is involved in the drought stress response of maize. Summary Statement: Drought stress adversely destroys maize development during the whole life cycle, finally reducing its yield and quality. Thus, improving the performance of maize against drought tolerance is a priority of breeding programs. Here, we identified a novel transcription factor ZmERF21 that is tightly associated with drought tolerance in maize seedlings. ZmERF21 is mainly expressed in root and leaf. Mechanistic analysis demonstrated that ZmERF21 could directly bind to the genes involved in hormone (ethylene, abscisic acid) and Ca signaling pathways. Furthermore, overexpression of ZmERF21 in maize significantly increased drought tolerance, evidenced by chlorophyll content and the activities of antioxidant enzymes. Taken together, our results revealed that ZmERF21 is a positive regulator in response to drought stress in maize. [ABSTRACT FROM AUTHOR]