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<jats:title>SUMMARY</jats:title><jats:p>Verticillium wilt (VW) is a devasting disease affecting various plants, including upland cotton, a crucial fiber crop. Despite its impact, the genetic basis underlying cotton's susceptibility or defense against VW remains unclear. Here, we conducted a genome‐wide association study on VW phenotyping in upland cotton and identified a locus on A13 that is significantly associated with VW resistance. We then identified a cystathionine β‐synthase domain gene at A13 locus, <jats:italic>GhCBSX3A</jats:italic>, which was induced by <jats:italic>Verticillium dahliae</jats:italic>. Functional analysis, including expression silencing in cotton and overexpression in <jats:italic>Arabidopsis thaliana</jats:italic>, confirmed that <jats:italic>GhCBSX3A</jats:italic> is a causal gene at the A13 locus, enhancing SAR‐RBOHs‐mediated apoplastic oxidative burst. We found allelic variation on the TATA‐box of <jats:italic>GhCBSX3A</jats:italic> promoter attenuated its expression in upland cotton, thereby weakening VW resistance. Interestingly, we discovered that altered artificial selection of <jats:italic>GhCBSX3A_R</jats:italic> (an elite allele for VW) under different VW pressures during domestication and other improved processes allows specific human needs to be met. Our findings underscore the importance of <jats:italic>GhCBSX3A</jats:italic> in response to VW, and we propose a model for defense‐associated genes being selected depending on the pathogen's pressure. The identified locus and gene serve as promising targets for VW resistance enhancement in cotton through genetic engineering.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>Genome‐wide association studies (GWAS) are an effective approach to identify new specialized metabolites and the genes involved in their biosynthesis and regulation. In this study, GWAS of <jats:italic>Arabidopsis thaliana</jats:italic> soluble leaf and stem metabolites identified alleles of an uncharacterized BAHD‐family acyltransferase (AT5G57840) associated with natural variation in three structurally related metabolites. These metabolites were esters of glucuronosylglycerol, with one metabolite containing phenylacetic acid as the acyl component of the ester. Knockout and overexpression of AT5G57840 in Arabidopsis and heterologous overexpression in <jats:italic>Nicotiana benthamiana</jats:italic> and <jats:italic>Escherichia coli</jats:italic> demonstrated that it is capable of utilizing phenylacetyl‐CoA as an acyl donor and glucuronosylglycerol as an acyl acceptor. We, thus, named the protein Glucuronosylglycerol Ester Synthase (GGES). Additionally, phenylacetyl glucuronosylglycerol increased in Arabidopsis CYP79A2 mutants that overproduce phenylacetic acid and was lost in knockout mutants of UDP‐sulfoquinovosyl: diacylglycerol sulfoquinovosyl transferase, an enzyme required for glucuronosylglycerol biosynthesis and associated with glycerolipid metabolism under phosphate‐starvation stress. GGES is a member of a well‐supported clade of BAHD family acyltransferases that arose by duplication and neofunctionalized during the evolution of the Brassicales within a larger clade that includes HCT as well as enzymes that synthesize other plant‐specialized metabolites. Together, this work extends our understanding of the catalytic diversity of BAHD acyltransferases and uncovers a pathway that involves contributions from both phenylalanine and lipid metabolism.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>In angiosperms, cyclic electron transport around photosystem I (PSI) is mediated by two pathways that depend on the PROTON GRADIENT REGULATION 5 (PGR5) protein and the chloroplast NADH dehydrogenase‐like (NDH) complex, respectively. In the Arabidopsis double mutants defective in both pathways, plant growth and photosynthesis are impaired. The <jats:italic>pgr5‐1</jats:italic> mutant used in the original study is a missense allele and accumulates low levels of PGR5 protein. In this study, we generated two knockout (KO) alleles, designated as <jats:italic>pgr5‐5</jats:italic> and <jats:italic>pgr5‐6</jats:italic>, using the CRISPR‐Cas9 technology. Although both KO alleles showed a severe reduction in P700 similar to the <jats:italic>pgr5‐1</jats:italic> allele, NPQ induction was less severely impaired in the KO alleles than in the <jats:italic>pgr5‐1</jats:italic> allele. In the <jats:italic>pgr5‐1</jats:italic> allele, the second mutation affecting NPQ size was mapped to ~21 cM south of the <jats:italic>pgr5‐1</jats:italic> locus. Overexpression of the <jats:italic>pgr5‐1</jats:italic> allele, encoding the glycine130‐to‐serine change, complemented the <jats:italic>pgr5‐5</jats:italic> phenotype, suggesting that the <jats:italic>pgr5‐1</jats:italic> mutation destabilizes PGR5 but that the mutant protein retains partial functionality. Using two KO alleles, we created the double mutants with two <jats:italic>chlororespiratory reduction</jats:italic> (<jats:italic>crr</jats:italic>) mutants defective in the NDH complex. The growth of the double mutants was notably impaired. In the double mutant seedlings that survived on the medium containing sucrose, PSI activity evaluated by the P700 oxidation was severely impaired, whereas PSII activity was only mildly impaired. Cyclic electron transport around PSI is required to maintain PSI activity.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>The Arabidopsis endoplasmic reticulum‐localized heat shock protein HSP90.7 modulates tissue differentiation and stress responses; however, complete knockout lines have not been previously reported. In this study, we identified and analyzed a mutant allele, <jats:italic>hsp90.7‐1</jats:italic>, which was unable to accumulate the HSP90.7 full‐length protein and showed seedling lethality. Microscopic analyses revealed its essential role in male and female fertility, trichomes and root hair development, proper chloroplast function, and apical meristem maintenance and differentiation. Comparative transcriptome and proteome analyses also revealed the role of the protein in a multitude of cellular processes. Particularly, the auxin‐responsive pathway was specifically downregulated in the <jats:italic>hsp90.7‐1</jats:italic> mutant seedlings. We measured a much‐reduced auxin content in both root and shoot tissues. Through comprehensive histological and molecular analyses, we confirmed PIN1 and PIN5 accumulations were dependent on the HSP90 function, and the TAA‐YUCCA primary auxin biosynthesis pathway was also downregulated in the mutant seedlings. This study therefore not only fulfilled a gap in understanding the essential role of HSP90 paralogs in eukaryotes but also provided a mechanistic insight on the ER‐localized chaperone in regulating plant growth and development via modulating cellular auxin homeostasis.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>Monoterpene synthases (MTSs) catalyze the first committed step in the biosynthesis of monoterpenoids, a class of specialized metabolites with particularly high chemical diversity in angiosperms. In addition to accomplishing a rate enhancement, these enzymes manage the formation and turnover of highly reactive carbocation intermediates formed from a prenyl diphosphate substrate. At each step along the reaction path, a cationic intermediate can be subject to cyclization, migration of a proton, hydride, or alkyl group, or quenching to terminate the sequence. However, enzymatic control of ligand folding, stabilization of specific intermediates, and defined quenching chemistry can maintain the specificity for forming a signature product. This review article will discuss our current understanding of how angiosperm MTSs control the reaction environment. Such knowledge allows inferences about the origin and regulation of chemical diversity, which is pertinent for appreciating the role of monoterpenoids in plant ecology but also for aiding commercial efforts that harness the accumulation of these specialized metabolites for the food, cosmetic, and pharmaceutical industries.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>Poor management and excess fertilization of apple (<jats:italic>Malus domestica</jats:italic> Borkh.) orchards are causing increasingly serious soil acidification, resulting in Al toxicity and direct poisoning of roots. Strigolactones (SLs) are reported to be involved in plant responses to abiotic stress, but their role and mechanism under AlCl<jats:sub>3</jats:sub> stress remain unknown. Here, we found that applying 1 μ<jats:sc>m</jats:sc> GR24 (an SL analoge) significantly alleviated AlCl<jats:sub>3</jats:sub> stress of M26 apple rootstock, mainly by blocking the movement of Al through cell wall and by vacuolar compartmentalization of Al. RNA‐seq analysis identified the core transcription factor gene <jats:italic>MdWRKY53</jats:italic>, and overexpressing <jats:italic>MdWRKY53</jats:italic> enhanced AlCl<jats:sub>3</jats:sub> tolerance in transgenic apple plants through the same mechanism as GR24. Subsequently, we identified <jats:italic>MdPMEI45</jats:italic> (encoding pectin methylesterase inhibitor) and <jats:italic>MdALS3</jats:italic> (encoding an Al transporter) as downstream target genes of MdWRKY53 using chromatin immunoprecipitation followed by sequencing (ChIP‐seq). GR24 enhanced the interaction between MdWRKY53 and the transcription factor MdTCP15, further increasing the binding of MdWRKY53 to the <jats:italic>MdPMEI45</jats:italic> promoter and inducing <jats:italic>MdPMEI45</jats:italic> expression to prevent Al from crossing cell wall. MdWRKY53 also bound to the promoter of <jats:italic>MdALS3</jats:italic> and enhanced its transcription to compartmentalize Al in vacuoles under AlCl<jats:sub>3</jats:sub> stress. We therefore identified two modules involved in alleviating AlCl<jats:sub>3</jats:sub> stress in woody plant apple: the SL‐WRKY+TCP‐PMEI module required for excluding external Al by blocking the entry of Al<jats:sup>3+</jats:sup> into cells and the SL‐WRKY‐ALS module allowing internal detoxification of Al through vacuolar compartmentalization. These findings lay a foundation for the practical application of SLs in agriculture.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>MicroRNAs are known to play a crucial role in plant development and physiology and become a target for investigating the regulatory mechanism underlying plant low phosphate tolerance. ZmmiR528 has been shown to display significantly different expression levels between wild‐type and low Pi‐tolerant maize mutants. However, its functional role in maize low Pi tolerance remains unknown. In the present study, we studied the role and underlying molecular mechanism of miR528 in maize with low Pi tolerance. Overexpression of ZmmiR528 in maize resulted in impaired root growth, reduced Pi uptake capacity and compromised resistance to Pi deficiency. By contrast, transgenic maize plants suppressing ZmmiR528 expression showed enhanced low Pi tolerance. Furthermore, <jats:italic>ZmLac3</jats:italic> and <jats:italic>ZmLac5</jats:italic> which encode laccase were identified and verified as targets of ZmmiR528. <jats:italic>ZmLac3</jats:italic> transgenic plants were subsequently generated and were also found to play key roles in regulating maize root growth, Pi uptake and low Pi tolerance. Furthermore, auxin transport was found to be potentially involved in <jats:italic>ZmLac3‐</jats:italic>mediated root growth. Moreover, we conducted genetic complementary analysis through the hybridization of ZmmiR528 and <jats:italic>ZmLac3</jats:italic> transgenic plants and found a favorable combination with breeding potential, namely anti‐miR528:<jats:italic>ZmLac3OE</jats:italic> hybrid maize, which exhibited significantly increased low Pi tolerance and markedly alleviated yield loss caused by low Pi stress. Our study has thus identified a ZmmiR528‐<jats:italic>ZmLac3</jats:italic> module regulating auxin transport and hence root growth, thereby determining Pi uptake and ultimately low Pi tolerance, providing an effective approach for low Pi tolerance improvement through manipulating the expression of miRNA and its target in maize.</jats:p>

<jats:title>SUMMARY</jats:title><jats:p>Stomata are pores at the leaf surface that enable gas exchange and transpiration. The signaling pathways that regulate the differentiation of stomatal guard cells and the mechanisms of stomatal pore formation have been characterized in <jats:italic>Arabidopsis thaliana</jats:italic>. However, the process by which stomatal complexes develop after pore formation into fully mature complexes is poorly understood. We tracked the morphogenesis of young stomatal complexes over time to establish characteristic geometric milestones along the path of stomatal maturation. Using 3D‐nanoindentation coupled with finite element modeling of young and mature stomata, we found that despite having thicker cell walls than young guard cells, mature guard cells are more energy efficient with respect to stomatal opening, potentially attributable to the increased mechanical anisotropy of their cell walls and smaller changes in turgor pressure between the closed and open states. Comparing geometric changes in young and mature guard cells of wild‐type and cellulose‐deficient plants revealed that although cellulose is required for normal stomatal maturation, mechanical anisotropy appears to be achieved by the collective influence of cellulose and additional wall components. Together, these data elucidate the dynamic geometric and biomechanical mechanisms underlying the development process of stomatal maturation.</jats:p>