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<jats:title>Abstract</jats:title><jats:p>Reactive oxygen species (ROS) are important signaling molecules in stomatal closure. In a previous report, we demonstrated that ROS generated through photosynthetic electron transport (PET) act as signaling molecules in abscisic acid (ABA)‐induced stomatal closure. However, the mechanism by which ABA induces ROS generation through PET remains unclear. Here, we assessed the possibility that chloroplast K<jats:sup>+</jats:sup>/H<jats:sup>+</jats:sup> EXCHANGE ANTIPORTER 3 (KEA3) functions in ABA‐induced ROS generation in guard cells, resulting in stomatal closure. KEA3 localizes to a thylakoid membrane and allows proton efflux from the thylakoid lumen by K<jats:sup>+</jats:sup>/H<jats:sup>+</jats:sup> antiport, regulating photosynthesis by proton motive force. KEA3 loss‐of‐function mutants (<jats:italic>kea3‐1</jats:italic> and <jats:italic>kea3‐2</jats:italic>) were impaired in ABA‐induced ROS generation of guard cells and stomatal closure. The small molecule electroneutral K<jats:sup>+</jats:sup>/H<jats:sup>+</jats:sup> antiporter nigericin induced ROS generation in guard cells and stomatal closures in the <jats:italic>kea3</jats:italic> mutants. This study demonstrates that KEA3 is an important factor for ABA‐induced ROS generation in guard cells and stomatal closure.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Heat shock transcription factor (Hsf) plays a pivotal role in promoting rapid heat‐induced transcriptional reprogramming in plants. The thermotolerance regulatory function of Hsfs is influenced by their own alternative splicing. In this study, we found that <jats:italic>ZmHsf17‐II</jats:italic>, an intron retention isoform of subclass A2 gene <jats:italic>ZmHsf17</jats:italic> of maize (<jats:italic>Zea mays</jats:italic>), accumulated in large amounts as a result of severe or sustained heat stress. It was confirmed by expression and purification that <jats:italic>ZmHsf17‐II</jats:italic> encodes a small truncated peptide with 115 amino acids. ZmHsf17‐II was found to be located in the nucleus and have no transcriptional activity. Overexpressing <jats:italic>ZmHsf17‐I</jats:italic> in Arabidopsis could enhance plants' thermotolerance, while overexpressing <jats:italic>ZmHsf17‐II</jats:italic> does not. Based on the results of molecular docking, Y2H and split LUC experiments, we found that ZmHsf17‐II could bind to DBD region of ZmHsf17‐I through the hydrogen bond interaction between the truncated DBD of ZmHsf17‐II and three amino acid residues (Arg105, Thr109 and Lys142) of ZmHsf17‐I DBD region. Further experiments showed that ZmHsf17‐I could bind to its own promoter and exhibited transcriptional activation activity, while ZmHsf17‐I interaction with ZmHsf17‐II, transcriptional activation activity was interfered. Those findings indicate that ZmHsf17 can negatively regulate its own transcription by producing more intron retention isoforms via alternative splicing under heat stress.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Due to the increasing impact of worldwide environmental changes, temperature stress has become a major factor resulting in crop yield losses. The discovery of temperature‐stress‐responsive protein‐coding genes has made significant progress in understanding plants' complex stress response systems involving microRNAs (miRNAs). The miRNAs are triggered by heat or cold, thus confirming their significant functional role in cold or heat tolerance. Such dependable recommendations significantly broaden our understanding of the regulatory role of miRNAs in plant stress responses. This article presents novel perspectives on the substantial roles of plant miRNAs in responding to and acclimatizing to heat and cold stress. It comprehensively elaborates on miRNAs responsive to temperature stress, their regulatory mechanisms, and their targeted functions in plants. Additionally, the article investigates how miRNAs contribute to safeguarding plant reproductive tissues, mitigating damage caused by reactive oxygen species, modulating heat shock proteins, transcription factors, and phytohormones in the context of temperature stress. The conclusion outlines potential avenues for future research, highlighting the utilization of miRNAs and their regulatory functions to develop economically vital crops with enhanced tolerance to temperature stress, thereby ensuring future food security.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Cotton (Gossypium spp.) is an economically important crop, but its productivity is often hindered by the soil‐borne pathogen <jats:italic>Verticillium dahliae</jats:italic>. This study aimed to investigate the response of cotton roots to <jats:italic>V. dahliae</jats:italic> infection by analysing the proteome of <jats:italic>Gossypium thurberi</jats:italic> (resistant) and <jats:italic>Gossypium raimondii</jats:italic> (susceptible) at 0 h, 24 h, and 48 h post‐infection. Through weighted protein coexpression network analysis, fifteen hub proteins crucial for defense against <jats:italic>V. dahliae</jats:italic> were identified. Expression analysis revealed the pivotal role of <jats:italic>GthGAPC2</jats:italic>, encoding GLYCERALDEHYDE‐3‐PHOSPHATE DEHYDROGENASE 2, in conferring resistance to <jats:italic>V. dahliae</jats:italic> in cotton. Virus‐induced gene Silencing (VIGS) of <jats:italic>GthGAPC2</jats:italic> increased susceptibility to <jats:italic>V. dahliae</jats:italic>, which was supported by oxidant and antioxidant enzyme activities. Furthermore, <jats:italic>GthGAPC2</jats:italic> silencing influenced lignin content, indicating its involvement in lignin biosynthesis regulation. Transient overexpression of <jats:italic>GthGAPC2</jats:italic> in tobacco supported its role in cell death processes. Subcellular localization studies showed predominant nuclear localization of <jats:italic>GthGAPC2</jats:italic>. Overexpression of <jats:italic>GthGAPC2</jats:italic> in Arabidopsis also confirms its significant role in <jats:italic>V. dahliae</jats:italic> resistance. These findings shed light on the molecular mechanisms of disease resistance in <jats:italic>Gossypium thurberi</jats:italic>. Identification of <jats:italic>GthGAPC2,</jats:italic> as a key protein involved in <jats:italic>V. dahliae</jats:italic> resistance, and its functional implications can aid breeding strategies for enhancing cotton's disease resistance.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Land‐plant transglycosylases ‘cut‐and‐paste’ cell‐wall polysaccharides by endo‐transglycosylation (transglycanases) and exo‐transglycosylation (transglycosidases). Such enzymes may remodel the wall, adjusting extensibility and adhesion. Charophytes have cell‐wall polysaccharides that broadly resemble, but appreciably differ from land‐plants'. We investigated whether <jats:italic>Chara vulgaris</jats:italic> has wall‐restructuring enzymes mirroring those of land‐plants.</jats:p><jats:p>Wall enzymes extracted from <jats:italic>Chara</jats:italic> were assayed <jats:italic>in vitro</jats:italic> for transglycosylase activities on various donor substrates — β‐(1→4)‐glucan‐based [xyloglucan and mixed‐linkage glucans (MLGs)], β‐(1→4)‐xylans and β‐(1→4)‐mannans — plus related acceptor substrates (tritium‐labelled oligosaccharides, XXXGol, Xyl<jats:sub>6</jats:sub>‐ol and Man<jats:sub>6</jats:sub>‐ol), thus 12 donor:acceptor permutations. Also, fluorescent oligosaccharides were incubated <jats:italic>in situ</jats:italic> with <jats:italic>Chara</jats:italic>, revealing endogenous enzyme action on endogenous (potentially novel) polysaccharides.</jats:p><jats:p><jats:italic>Chara</jats:italic> enzymes acted on the glucan‐based polysaccharides with [<jats:sup>3</jats:sup>H]XXXGol as acceptor substrate, demonstrating ‘glucan:glucan‐type’ transglucanases. Such activities were unexpected because <jats:italic>Chara</jats:italic> lacks biochemically detectable xyloglucan and MLG. With xylans as donor and [<jats:sup>3</jats:sup>H]Xyl<jats:sub>6</jats:sub>‐ol (but not [<jats:sup>3</jats:sup>H]Man<jats:sub>6</jats:sub>‐ol) as acceptor, high trans‐β‐xylanase activity was detected. With mannans as donor and either [<jats:sup>3</jats:sup>H]Man<jats:sub>6</jats:sub>‐ol or [<jats:sup>3</jats:sup>H]Xyl<jats:sub>6</jats:sub>‐ol as acceptor, we detected high levels of both mannan:mannan homo‐trans‐β‐mannanase and mannan:xylan hetero‐trans‐β‐mannanase activity, showing that <jats:italic>Chara</jats:italic> can not only ‘cut/paste’ these hemicelluloses by homo‐transglycosylation but also <jats:styled-content>hetero</jats:styled-content>‐transglycosylate them, forming mannan→xylan (but not xylan→mannan) hybrid hemicelluloses. In <jats:italic>in‐situ</jats:italic> assays, <jats:italic>Chara</jats:italic> walls attached endogenous polysaccharides to exogenous sulphorhodamine‐labelled Man<jats:sub>6</jats:sub>‐ol, indicating transglycanase (possibly trans‐mannanase) action on endogenous polysaccharides.</jats:p><jats:p>In conclusion, cell‐wall transglycosylases, comparable to but different from those of land‐plants, pre‐dated the divergence of the Charophyceae from its sister clade (Coleochaetophyceae/Zygnematophyceae/land‐plants). Thus, the ability to ‘cut/paste’ wall polysaccharides is an evolutionarily ancient streptophytic trait.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Sorghum (<jats:italic>Sorghum bicolor</jats:italic> L. Moench) is the world's fifth most‐produced cereal. The wall‐associated kinases (WAKs) gene family plays a crucial regulatory role in various aspects of plant biology, including the response to environmental stress and pathogens. Therefore, we aimed to characterize the members of the WAK gene family in sorghum using bioinformatics tools and to determine their functional roles in heat stress by detecting transcript levels using RT‐qPCR. A total of 98 SbWAK/SbWAKL proteins were identified and classified into six phylogenetic groups. The <jats:italic>SbWAKs/SbWAKL</jats:italic> genes were unevenly distributed across ten chromosomes, and 33 duplications were observed on nine chromosomes. The number of amino acids and molecular weight of SbWAKs/SbWAKLs ranged from 496 to 1149 aa and 55.38 to 124.89 kDa, respectively. Forty‐eight SbWAK/SbWAKL were unstable, with an instability index greater than 40. The synteny analyses revealed sixteen <jats:italic>SbWAK/SbWAKL</jats:italic> genes similar in foxtail millet, thirteen in maize, and seven in the rice genome. Additionally, 107 miRNAs, including cell wall‐related miRNAs, targeted 85 <jats:italic>SbWAK/SbWAKL</jats:italic> genes. The <jats:italic>cis</jats:italic>‐acting elements in <jats:italic>SbWAK/SbWAKL</jats:italic> genes pointed out that these genes may be associated with light, hormone, development, and environmental stress responses. RT‐qPCR analysis of 13 <jats:italic>SbWAK/SbWAKL</jats:italic> genes revealed a relatively high transcript fold change in 6 <jats:italic>SbWAK/SbWAKL</jats:italic> under high‐temperature conditions. In conclusion, <jats:italic>cis</jats:italic>‐acting elements, protein–protein and miRNA interactions, and higher gene expression levels at high temperatures may indicate the existence of candidate <jats:italic>SbWAKs/SbWAKLs</jats:italic> genes with functions in abiotic and biotic stress response and their usage in future gene editing for breeding purposes.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Gamma‐aminobutyric acid (GABA), a ubiquitously present non‐proteinogenic amino acid, has recently emerged as a key regulator of growth and development in plants during normal as well as challenging environmental conditions. GABA biosynthesis has been reported at multiple stages of plant development, particularly during vegetative and reproductive stages and in response to stress conditions. Accumulating evidence has highlighted the crucial roles of various cell cycle regulators such as type‐D cyclins and CDK;A1, transcription factors such as E2Fa, as well as Ca<jats:sup>2+/</jats:sup>Calmodulin proteins in GABA biosynthesis in plants. GABA is known to improve stress tolerance by improving photosynthetic activity, C/N metabolism, stomatal conductance, and stress‐induced reactive oxygen species (ROS) detoxification. Here, we have reviewed recent studies that have explored the novel roles of GABA in plants with a focus on plant development and stress resilience.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Phycobiliproteins (PBPs) play a vital role in light harvesting by cyanobacteria, which enables efficient utilization of photon energy for oxygenic photosynthesis. The PBPs carry phycobilins, open‐chain tetrapyrrole chromophores derived from heme. The structure and chromophore composition of PBPs is dependent on the organism's ecological niche. In cyanobacteria, these holo‐proteins typically form large, macromolecular antenna complexes called phycobilisomes (PBSs). The PBS of <jats:italic>Synechocystis</jats:italic> sp. PCC 6803 (hereafter <jats:italic>Synechocystis</jats:italic>) consists of allophycocyanin (APC) and phycocyanin (PC), which exclusively harbor phycocyanobilin (PCB) as a chromophore. Investigations into heterologous PBP biosynthesis in <jats:italic>E. coli</jats:italic> have proven limiting with respect to PBP assembly and their functional characterization. Consequently, we wanted to engineer a platform for the investigation of heterologously produced PBPs, focusing on unusual, phycoerythrobilin (PEB)‐containing light‐harvesting proteins called phycoerythrins (PEs) in <jats:italic>Synechocystis</jats:italic>. As a first step, a gene encoding for the synthesis of the natural cyanobacterial chromophore, PEB, was introduced into <jats:italic>Synechocystis</jats:italic>. We provide spectroscopic evidence for heterologous PEB formation and show covalent attachment of PEB to the α‐subunit of PC, CpcA, by HPLC and LC–MS/MS analyses. Fluorescence microscopy and PBS isolation demonstrate a cellular dispersal of PBPs with modified phycobilin content. However, these modifications have minor effects on physiological responses, as demonstrated by growth rates, oxygen evolution, nutrient accumulation, and PBP content analyses. As a result, <jats:italic>Synechocystis</jats:italic> demonstrates the capacity to efficiently manage PEB biosynthesis and therefore reflects a promising platform for both biochemical and physiological investigations of foreign and unusual PEs.</jats:p>