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Summary: Cold stress affects crop growth and productivity worldwide. Understanding the genetic basis of cold tolerance in germplasms is critical for crop improvement. Plants can coordinate environmental stimuli of light and temperature to regulate cold tolerance. However, it remains unknown which gene in germplasms could have such function. Here, we utilized genome‐wide association study (GWAS) to investigate the cold tolerance of wild and cultivated tomato accessions and discovered that increased cold tolerance is accompanied with tomato domestication. We further identified a 27‐bp InDel in the promoter of the CONSTANS‐like transcription factor (TF) SlBBX31 is significantly linked with cold tolerance. Coincidentally, a key regulator of light signalling, SlHY5, can directly bind to the SlBBX31 promoter to activate SlBBX31 transcription while the 27‐bp InDel can prevent S1HY5 from transactivating SlBBX31. Parallel to these findings, we observed that the loss of function of SlBBX31 results in impaired tomato cold tolerance. SlBBX31 can also modulate the cold‐induced expression of several ERF TFs including CBF2 and DREBs. Therefore, our study has uncovered that SlBBX31 is possibly selected during tomato domestication for cold tolerance regulation, providing valuable insights for the development of hardy tomato varieties. [ABSTRACT FROM AUTHOR]

Summary: CDK8 is a key subunit of Mediator complex, a large multiprotein complex that is a fundamental part of the conserved eukaryotic transcriptional machinery. However, the biological functions of CDK8 in plant abiotic stress responses remain largely unexplored.Here, we demonstrated CDK8 as a critical regulator in the abscisic acid (ABA) signaling and drought response pathways in Arabidopsis. Compared to wild‐type, cdk8 mutants showed reduced sensitivity to ABA, impaired stomatal apertures and hypersensitivity to drought stress. Transcriptomic and chromatin immunoprecipitation analysis revealed that CDK8 positively regulates the transcription of several ABA‐responsive genes, probably through promoting the recruitment of RNA polymerase II to their promoters.We discovered that both CDK8 and SnRK2.6 interact physically with an ERF/AP2 transcription factor RAP2.6, which can directly bind to the promoters of RD29A and COLD‐REGULATED 15A (COR15A) with GCC or DRE elements, thereby promoting their expression. Importantly, we also showed that CDK8 is essential for the ABA‐induced expression of RAP2.6 and RAP2.6‐mediated upregulation of ABA‐responsive genes, indicating that CDK8 could link the SnRK2.6‐mediated ABA signaling to RNA polymerase II to promote immediate transcriptional response to ABA and drought signals.Overall, our data provide new insights into the roles of CDK8 in modulating ABA signaling and drought responses. [ABSTRACT FROM AUTHOR]

CLAVATA1 ( CLV1) is a receptor protein expressed in the shoot apical meristem ( SAM) that translates perception of a non-cell-autonomous CLAVATA3 ( CLV3) peptide signal into altered stem cell fate. CLV3 reduces expression of WUSCHEL ( WUS) and FANTASTIC FOUR 2 ( FAF2) in the SAM. Expression of WUS and FAF2 leads to maintenance of undifferentiated stem cells in the SAM. CLV3 binding to CLV1 inhibits expression of these genes and controls stem cell fate in the SAM through an unidentified signaling pathway. Cytosolic Ca2+ elevations, cyclic nucleotide ( cGMP)-activated Ca2+ channels, and cGMP have been linked to signaling downstream of receptors similar to CLV1. Hence, we hypothesized that cytosolic Ca2+ elevation mediates the CLV3 ligand/ CLV1 receptor signaling that controls meristem stem cell fate. CLV3 application to Arabidopsis seedlings results in elevation of cytosolic Ca2+ and cGMP. CLV3 control of WUS was prevented in a genotype lacking a functional cGMP-activated Ca2+ channel. In wild-type plants, CLV3 inhibition of WUS and FAF2 expression was impaired by treatment with either a Ca2+ channel blocker or a guanylyl cyclase inhibitor. When CLV3-dependent repression of WUS is blocked, altered control of stem cell fate leads to an increase in SAM size; we observed a larger SAM size in seedlings treated with the Ca2+ channel blocker. These results suggest that the CLV3 ligand/ CLV1 receptor system initiates a signaling cascade that elevates cytosolic Ca2+, and that this cytosolic secondary messenger is involved in the signal transduction cascade linking CLV3/ CLV1 to control of gene expression and stem cell fate in the SAM. [ABSTRACT FROM AUTHOR]

SUMMARY: Uncovering the function of phytopathogen effectors is crucial for understanding mechanisms of pathogen pathogenicity and for improving our ability to protect plants from diseases. An increasing number of effectors have been predicted in various plant pathogens. Functional characterization of these effectors has become a major focus in the study of plant–pathogen interactions. In this study, we designed a novel screening system that combines the TMV (tobacco mosaic virus)‐GFP vector and Agrobacterium‐mediated transient expression in the model plant Nicotiana benthamiana. This system enables the rapid identification of effectors that interfere with plant immunity. The biological function of these effectors can be easily evaluated by observing the GFP fluorescence signal using a UV lamp within just a few days. To evaluate the TMV‐GFP system, we initially tested it with well‐described virulence and avirulence type III effectors from the bacterial pathogen Ralstonia solanacearum. After proving the accuracy and efficiency of the TMV‐GFP system, we successfully screened a novel virulence effector, RipS1, using this approach. Furthermore, using the TMV‐GFP system, we reproduced consistent results with previously known cytoplasmic effectors from a diverse array of pathogens. Additionally, we demonstrated the effectiveness of the TMV‐GFP system in identifying apoplastic effectors. The easy operation, time‐saving nature, broad effectiveness, and low technical requirements of the TMV‐GFP system make it a promising approach for high‐throughput screening of effectors with immune interference activity from various pathogens. Significance Statement: The development of a robust high‐throughput functional screening assay for pathogen effectors will facilitate the study in plant‐pathogen interactions. We established a novel screening system using the TMV‐GFP vector, enabling the rapid identification of effectors that interfere with plant immunity by observing GFP fluorescence under a UV lamp within a few days. The TMV‐GFP system is a promising approach for high‐throughput screening of effectors from diverse pathogens. [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 is a major abiotic stress that limits maize production worldwide. Therefore, it is of great importance to improve drought tolerance in crop plants for sustainable agriculture. In this study, we examined the roles of Cys2/His2 zinc‐finger‐proteins (C2H2‐ZFPs) in maize's drought tolerance as C2H2‐ZFPs have been implicated for plant stress tolerance. By subjecting 150 Ac/Ds mutant lines to drought stress, we successfully identified a Ds‐insertion mutant, zmc2h2‐149, which shows increased tolerance to drought stress. Overexpression of ZmC2H2‐149 in maize led to a decrease in both drought tolerance and crop yield. DAP‐Seq, RNA‐Seq, Y1H and LUC assays additionally showed that ZmC2H2‐149 directly suppresses the expression of a positive drought tolerance regulator, ZmHSD1 (hydroxysteroid dehydrogenase 1). Consistently, the zmhsd1 mutants exhibited decreased drought tolerance and grain yield under water deficit conditions compared to their respective wild‐type plants. Our findings thus demonstrated that ZmC2H2‐149 can regulate ZmHSD1 for drought stress tolerance in maize, offering valuable theoretical and genetic resources for maize breeding programmes that aim for improving drought tolerance. [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]

Summary: The domestication gene Q is largely responsible for the widespread cultivation of wheat because it confers multiple domestication traits. However, the underlying molecular mechanisms of how Q regulates these domestication traits remain unclear.In this study, we identify a Q‐interacting protein TaLAX1, a basic helix–loop–helix transcription factor, through yeast two‐hybrid assays. Using biochemical and genetic approaches, we explore the roles of TaLAX1 in regulating wheat domestication traits.Overexpression of TaLAX1 produces phenotypes, reminiscent of the q allele; loss‐of‐function Talax1 mutations confer compact spikes, largely similar to the Q‐overexpression wheat lines. The two transcription factors TaLAX1 and Q disturb each other's activity to antagonistically regulate the expression of the lignin biosynthesis‐related gene TaKNAT7‐4D. More interestingly, a natural variation (InDel, +/− TATA), which occurs in the promoter of TaLAX1, is associated with the promoter activity difference between the D subgenome of bread wheat and its ancestor Aegilops tauschii accession T093.This study reveals that the transcription factor TaLAX1 physically interacts with Q to antagonistically regulate wheat domestication traits and a natural variation (InDel, +/− TATA) is associated with the diversification of TaLAX1 promoter activity. [ABSTRACT FROM AUTHOR]

MED25 has been implicated as a negative regulator of the abscisic acid (ABA) signaling pathway. However, it is unclear whether other Mediator subunits could associate with MED25 to participate in the ABA response. Here, we used affinity purification followed by mass spectrometry to uncover Mediator subunits that associate with MED25 in transgenic plants. We found that at least 26 Mediator subunits, belonging to the head, middle, tail, and CDK8 kinase modules, were co‐purified with MED25 in vivo. Interestingly, the tail module subunit MED16 was identified to associate with MED25 under both mock and ABA treatments. We further showed that the disruption of MED16 led to reduced ABA sensitivity compared to the wild type. Transcriptomic analysis revealed that the expression of several ABA‐responsive genes was significantly lower in med16 than those in wild type. Furthermore, we discovered that MED16 may possibly compete with MED25 to interact with the key transcription factor ABA INSENSITIVE 5 (ABI5) to positively regulate ABA signaling. Consistently, med16 and med25 mutants displayed opposite phenotypes in ABA response, cuticle permeability, and differential ABI5‐mediated EM1 and EM6 expression. Together, our data indicate that MED16 and MED25 differentially regulate ABA signaling by antagonistically affecting ABI5‐mediated transcription in Arabidopsis. [ABSTRACT FROM AUTHOR]

Domestication has resulted in reduced salt tolerance in tomato. To identify the genetic components causing this deficiency, we performed a genome‐wide association study (GWAS) for root Na+/K+ ratio in a population consisting of 369 tomato accessions with large natural variations. The most significant variations associated with root Na+/K+ ratio were identified within the gene SlHAK20 encoding a member of the clade IV HAK/KUP/KT transporters. We further found that SlHAK20 transports Na+ and K+ and regulates Na+ and K+ homeostasis under salt stress conditions. A variation in the coding sequence of SlHAK20 was found to be the causative variant associated with Na+/K+ ratio and confer salt tolerance in tomato. Knockout mutations in tomato SlHAK20 and the rice homologous genes resulted in hypersensitivity to salt stress. Together, our study uncovered a previously unknown molecular mechanism of salt tolerance responsible for the deficiency in salt tolerance in cultivated tomato varieties. Our findings provide critical information for molecular breeding to improve salt tolerance in tomato and other crops. Synopsis: Selection of large fruits in domesticated tomato is linked to a reduction in salt tolerance. This study links domestication‐associated variation in the Na+/K+ transporter‐coding gene SlHAK20 to reduced salt tolerance in cultivated plants. Root Na+/K+ ratios show a strong positive correlation with fruit weight during tomato domestication.A variation in SlHAK20 is associated with Na+/K+ ratio modulation in tomato roots under salt stress conditions.The SlHAK20Hap1 haplotype is more effective than SlHAK20Hap2 in conferring Na+ homeostasis and salt tolerance.The role of SlHAK20 in regulation of salt tolerance is conserved in rice. [ABSTRACT FROM AUTHOR]

* Systemin (SYS), an octadecapeptide hormone processed from a 200-amino-acid precursor (prosystemin, PS), plays a central role in the systemic activation of defense genes in tomato in response to herbivore and pathogen attacks. However, whether PS mRNA is transferable and its role in systemic defense responses remain unknown. * We created the transgenic tomato PS gene tagged with the green fluorescent protein (PS-GFP) using a shoot- or root-specific promoter, and the constitutive 35S promoter in Arabidopsis. Subcellular localization of PS-/SYS-GFP was observed using confocal laser scanning microscopy and gene transcripts were determined using quantitative real-time PCR. * In Arabidopsis, PS protein can be processed and SYS is secreted. Shoot-/root-specific expression of PS-GFP in Arabidopsis, and grafting experiments, revealed that the PS mRNA moves in a bi-directional manner. We also found that ectopic expression of PS improves Arabidopsis resistance to the necrotrophic fungus Botrytis cinerea, consistent with substantial upregulation of the transcript levels of specific pathogen-responsive genes. * Our results provide novel insights into the multifaceted mechanism of SYS signaling transport and its potential application in genetic engineering for increasing pathogen resistance across diverse plant families. [ABSTRACT FROM AUTHOR]

Arabidopsis hypersensitive-induced reaction (At HIR) proteins function in plant innate immunity. However, the underlying mechanisms by which At HIRs participate in plant immunity remain elusive. Here, using VA- TIRFM and FLIM- FRET, we revealed that At HIR1 is present in membrane microdomains and co-localizes with the membrane microdomain marker REM1.3. Single-particle tracking analysis revealed that membrane microdomains and the cytoskeleton, especially microtubules, restrict the lateral mobility of At HIR1 at the plasma membrane and facilitate its oligomerization. Furthermore, protein proximity index measurements, fluorescence cross-correlation spectroscopy, and biochemical experiments demonstrated that the formation of the At HIR1 complex upon pathogen perception requires intact microdomains and cytoskeleton. Taken together, these findings suggest that microdomains and the cytoskeleton constrain At HIR1 dynamics, promote At HIR1 oligomerization, and increase the efficiency of the interactions of At HIR1 with components of the At HIR1 complex in response to pathogens, thus providing valuable insight into the mechanisms of defense-related responses in plants. [ABSTRACT FROM AUTHOR]