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Summary: Cold stress is a major abiotic stress that threatens maize (Zea mays L.) production worldwide. Understanding the molecular mechanisms underlying cold tolerance is crucial for breeding resilient maize varieties. Tonoplast intrinsic proteins (TIPs) are a subfamily of aquaporins in plants. Here, we report that TIP family proteins are involved in maize cold tolerance. The expression of most TIP genes was responsive to cold stress. Overexpressing TIP2;1, TIP3;2 or TIP4;3 reduced the cold tolerance of maize seedlings, while loss‐of‐function mutants of TIP4;3 exhibited enhanced cold tolerance. Candidate gene‐based association analysis revealed that a 328‐bp transposon insertion in the promoter region of TIP4;3 was strongly associated with maize cold tolerance. This transposon insertion conferred cold tolerance by repressing TIP4;3 expression through increased methylation of its promoter region. Moreover, TIP4;3 was found to suppress stomatal closure and facilitate reactive oxygen species (ROS) accumulation under cold stress, thereby inhibiting the expression of cold‐responsive genes, including DEHYDRATION‐RESPONSIVE ELEMENT BINDING FACTOR 1 (DREB1) genes and a subset of peroxidase genes, ultimately attenuating maize cold tolerance. This study thus elucidates the mechanism underlying TIP‐mediated cold tolerance and identifies a favourable TIP4;3 allele as a potential genetic resource for breeding cold‐tolerant maize varieties. [ABSTRACT FROM AUTHOR]

Drought has a significant, negative impact on crop production; and these effects are poised to increase with climate change. Plants acclimate to drought and water stress through diverse physiological responses, primarily mediated by the hormone abscisic acid (ABA). Because plants lose the majority of their water through stomatal pores on aerial surfaces of plants, stomatal closure is one of the rapid responses mediated by ABA to reduce transpirational water loss. The dynamic changes in the transcriptome of stomatal guard cells in response to ABA have been investigated in the model plant Arabidopsis thaliana. However, guard cell transcriptomes have not been analyzed in agronomically valuable crops such as a major oilseed crop, rapeseed. In this study, we investigated the dynamics of ABA-regulated transcriptomes in stomatal guard cells of Brassica napus and conducted comparison analysis with the transcriptomes of A. thaliana. We discovered changes in gene expression indicating alterations in a host of physiological processes, including stomatal movement, metabolic reprogramming, and light responses. Our results suggest the existence of both immediate and delayed responses to ABA in Brassica guard cells. Furthermore, the transcription factors and regulatory networks mediating these responses are compared to those identified in Arabidopsis. Our results imply the continuing evolution of ABA responses in Brassica since its divergence from a common ancestor, involving both protein-coding and non-coding nucleotide sequences. Together, our results will provide a basis for developing strategies for molecular manipulation of drought tolerance in crop plants. [ABSTRACT FROM AUTHOR]

Copyright of Biology Teaching is the property of East China Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Drought has a significant, negative impact on crop production; and these effects are poised to increase with climate change. Plants acclimate to drought and water stress through diverse physiological responses, primarily mediated by the hormone abscisic acid (ABA). Because plants lose the majority of their water through stomatal pores on aerial surfaces of plants, stomatal closure is one of the rapid responses mediated by ABA to reduce transpirational water loss. The dynamic changes in the transcriptome of stomatal guard cells in response to ABA have been investigated in the model plant Arabidopsis thaliana. However, guard cell transcriptomes have not been analyzed in agronomically valuable crops such as a major oilseed crop, rapeseed. In this study, we investigated the dynamics of ABA-regulated transcriptomes in stomatal guard cells of Brassica napus and conducted comparison analysis with the transcriptomes of A. thaliana. We discovered changes in gene expression indicating alterations in a host of physiological processes, including stomatal movement, metabolic reprogramming, and light responses. Our results suggest the existence of both immediate and delayed responses to ABA in Brassica guard cells. Furthermore, the transcription factors and regulatory networks mediating these responses are compared to those identified in Arabidopsis. Our results imply the continuing evolution of ABA responses in Brassica since its divergence from a common ancestor, involving both protein-coding and non-coding nucleotide sequences. Together, our results will provide a basis for developing strategies for molecular manipulation of drought tolerance in crop plants.

Calcium oscillations are induced by different stresses. Calcium‐dependent protein kinases (CDPKs/CPKs) are one major group of the plant calcium decoders that are involved in various processes including drought response. Some CPKs are calcium‐independent. Here, we identified ZmCPK2 as a negative regulator of drought resistance by screening an overexpression transgenic maize pool. We found that ZmCPK2 does not bind calcium, and its activity is mainly inhibited during short term abscisic acid (ABA) treatment, and dynamically changed in prolonged treatment. Interestingly, ZmCPK2 interacts with and is inhibited by calcium‐dependent ZmCPK17, a positive regulator of drought resistance, which is activated by ABA. ZmCPK17 could prevent the nuclear localization of ZmCPK2 through phosphorylation of ZmCPK2T60. ZmCPK2 interacts with and phosphorylates and activates ZmYAB15, a negative transcriptional factor for drought resistance. Our results suggest that drought stress‐induced Ca2+ can be decoded directly by ZmCPK17 that inhibits ZmCPK2, thereby promoting plant adaptation to water deficit. [ABSTRACT FROM AUTHOR]

Cucumber (Cucumis sativus L.) is a globally prevalent and extensively cultivated vegetable whose yield is significantly influenced by various abiotic stresses, including drought, heat, and salinity. Transcription factors, such as zinc finger-homeodomain proteins (ZHDs), a plant-specific subgroup of Homeobox, play a crucial regulatory role in stress resistance. In this study, we identified 13 CsZHDs distributed across all six cucumber chromosomes except chromosome 7. Phylogenetic analysis classified these genes into five clades (ZHDI-IV and MIF) with different gene structures but similar conserved motifs. Collinearity analysis revealed that members of clades ZHD III, IV, and MIF experienced amplification through segmental duplication events. Additionally, a closer evolutionary relationship was observed between the ZHDs in Cucumis sativus (C. sativus) and Arabidopsis thaliana (A. thaliana) compared to Oryza sativa (O. sativa). Quantitative real-time PCR (qRT-PCR) analysis demonstrated the general expression of CsZHD genes across all tissues, with notable expression in leaf and flower buds. Moreover, most of the CsZHDs, particularly CsZHD9-11, exhibited varying responses to drought, heat, and salt stresses. Virus-induced gene silencing (VIGS) experiments highlighted the potential functions of CsZHD9 and CsZHD10, suggesting their positive regulation of stomatal movement and responsiveness to drought stress. In summary, these findings provide a valuable resource for future analysis of potential mechanisms underlying CsZHD genes in response to stresses. [ABSTRACT FROM AUTHOR]

Background: Vicia faba L. is a significant grain legume that is rich in protein and nutrients. It is widely cultivated for human consumption and animal feed in temperate regions. As a signaling molecule, fructose is involved in many metabolic and developmental processes. The objective of this study was to demonstrate whether fructose may increase reactive oxygen species (ROS) production in guard cells inducing stomatal closure and examine whether the exogenous application of fructose may regulate photosynthesis and chlorophyll fluorescence characteristics. Methods: After approximately 4 weeks of sowing the treated broad bean seeds, the fully inflated leaves were used for experimental data collection including stomatal movement, gas exchange, chlorophyll fluorescence and ROS production in guard cells. Result: Fructose reduced stomatal conductance (Gs), transpiration rate (Tr) and stomatal aperture of intact leaves, indicating that fructose can trigger stomatal closure in a dose- and time-dependent manner in the epidermal peels of the broad bean plant (Vicia faba L.). Meanwhile, fructose increased the photochemical efficiency, photosynthetic rate (Pn) and water use efficiency (WUE). Fructose-induced stomatal closure was associated with nitric oxide (NO), calcium ion (Ca2+), aquaporin and ROS. [ABSTRACT FROM AUTHOR]

The regulation of stomatal aperture opening and closure represents an evolutionary battle between plants and pathogens, characterized by adaptive strategies that influence both plant resistance and pathogen virulence. The ongoing climate change introduces further complexity, affecting pathogen invasion and host immunity. This review delves into recent advances on our understanding of the mechanisms governing immunity-related stomatal movement and patterning with an emphasis on the regulation of stomatal opening and closure dynamics by pathogen patterns and host phytocytokines. In addition, the review explores how climate changes impact plant–pathogen interactions by modulating stomatal behavior. In light of the pressing challenges associated with food security and the unpredictable nature of climate changes, future research in this field, which includes the investigation of spatiotemporal regulation and engineering of stomatal immunity, emerges as a promising avenue for enhancing crop resilience and contributing to climate control strategies. Precise regulation of stomatal movement ensures plant resilience against pathogen infections and ever-fluctuating dynamics of the environment. This review navigates recent progress in revealing the intricate signaling mechanisms governing stomatal movement dynamics and patterning in plants upon pathogen infections under the shifting climate paradigms. [ABSTRACT FROM AUTHOR]

Hyperosmotic stress caused by drought is a detrimental threat to plant growth and agricultural productivity due to limited water availability. Stomata are gateways of transpiration and gas exchange, the swift adjustment of stomatal aperture has a strong influence on plant drought resistance. Despite intensive investigations of stomatal closure during drought stress in past decades, little is known about how sequential signals are integrated during complete processes. Here, we discovered that the rapid Ca2+ signaling and subsequent abscisic acid (ABA) signaling contribute to the kinetics of both F-actin reorganizations and stomatal closure in Arabidopsis thaliana, while STOMATAL CLOSURE-RELATED ACTIN BINDING PROTEIN1 (SCAB1) is the molecular switch for this entire process. During the early stage of osmotic shock responses, swift elevated calcium signaling promotes SCAB1 phosphorylation through calcium sensors CALCIUM DEPENDENT PROTEIN KINASE3 (CPK3) and CPK6. The phosphorylation restrained the microfilament binding affinity of SCAB1, which bring about the F-actin disassembly and stomatal closure initiation. As the osmotic stress signal continued, both the kinase activity of CPK3 and the phosphorylation level of SCAB1 attenuated significantly. We further found that ABA signaling is indispensable for these attenuations, which presumably contributed to the actin filament reassembly process as well as completion of stomatal closure. Notably, the dynamic changes of SCAB1 phosphorylation status are crucial for the kinetics of stomatal closure. Taken together, our results support a model in which SCAB1 works as a molecular switch, and directs the microfilament rearrangement through integrating the sequentially generated Ca2+ and ABA signals during osmotic stress induced stomatal closure. [ABSTRACT FROM AUTHOR]

Abstract Background Astragalus grows mainly in drought areas. Cycloastragenol (CAG) is a tetracyclic triterpenoid allelochemical extracted from traditional Chinese medicine Astragalus root. Phospholipase C (PLC) and Gα-submit of the heterotrimeric G-protein (GPA1) are involved in many biotic or abiotic stresses. Nitric oxide (NO) is a crucial gas signal molecule in plants. Results In this study, using the seedlings of Arabidopsis thaliana (A. thaliana), the results showed that low concentrations of CAG induced stomatal closure, and high concentrations inhibited stomatal closure. 30 µmol·L−1 CAG significantly increased the relative expression levels of PLC1 and GPA1 and the activities of PLC and GTP hydrolysis. The stomatal aperture of plc1, gpa1, and plc1/gpa1 was higher than that of WT under CAG treatment. CAG increased the fluorescence intensity of NO in guard cells. Exogenous application of c-PTIO to WT significantly induced stomatal aperture under CAG treatment. CAG significantly increased the relative expression levels of NIA1 and NOA1. Mutants of noa1, nia1, and nia2 showed that NO production was mainly from NOA1 and NIA1 by CAG treatment. The fluorescence intensity of NO in guard cells of plc1, gpa1, and plc1/gpa1 was lower than WT, indicating that PLC1 and GPA1 were involved in the NO production in guard cells. There was no significant difference in the gene expression of PLC1 in WT, nia1, and noa1 under CAG treatment. The gene expression levels of NIA1 and NOA1 in plc1, gpa1, and plc1/gpa1 were significantly lower than WT, indicating that PLC1 and GPA1 were positively regulating NO production by regulating the expression of NIA1 and NOA1 under CAG treatment. Conclusions These results suggested that the NO accumulation was essential to induce stomatal closure under CAG treatment, and GPA1 and PLC1 acted upstream of NO.

Introduction: Drought is the principal abiotic stress that severely impacts cotton (Gossypium hirsutum) growth and productivity. Upon sensing drought, plants activate stress-related signal transduction pathways, including ABA signal and mitogen-activated protein kinase (MAPK) cascade. However, as the key components with the fewest members in the MAPK cascade, the function and regulation of GhMKKs need to be elucidated. In addition, the relationship between MAPK module and the ABA core signaling pathway remains incompletely understood. Objective: Here we aim to elucidate the molecular mechanism of cotton response to drought, with a focus on mitogen-activated protein kinase (MAPK) cascades activating ABA signaling. Methods: Biochemical, molecular and genetic analysis were used to study the GhMAP3K62-GhMKK16-GhMPK32-GhEDT1 pathway genes. Results: A nucleus- and membrane-localized MAPK cascade pathway GhMAP3K62-GhMKK16-GhMPK32, which targets and phosphorylates the nuclear-localized transcription factor GhEDT1, to activate downstream GhNCED3 to mediate ABA-induced stomatal closure and drought response was characterized in cotton. Overexpression of GhMKK16 promotes ABA accumulation, and enhances drought tolerance via regulating stomatal closure under drought stress. Conversely, RNAi-mediated knockdown of GhMKK16 expression inhibits ABA accumulation, and reduces drought tolerance. Virus-induced gene silencing (VIGS)-mediated knockdown of either GhMAP3K62, GhMPK32 or GhEDT1 expression represses ABA accumulation and reduces drought tolerance through inhibiting stomatal closure. Expression knockdown of GhMPK32 or GhEDT1 in GhMKK16-overexpressing cotton reinstates ABA content and stomatal opening-dependent drought sensitivity to wild type levels. GhEDT1 could bind to the HD boxes in the promoter of GhNCED3 to activate its expression, resulting in ABA accumulation. We propose that the MAPK cascade GhMAP3K62-GhMKK16-GhMPK32 pathway functions on drought response through ABA-dependent stomatal movement in cotton.

Copyright of Biology Teaching is the property of East China Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The natural variation between Arabidopsis (Arabidopsis thaliana) ecotypes Columbia (Col) and Landsberg erecta (Ler) strongly affects abscisic acid (ABA) signalling and drought tolerance. Here, we report that the cysteine‐rich receptor‐like protein kinase CRK4 is involved in regulating ABA signalling, which contributes to the differences in drought stress tolerance between Col‐0 and Ler‐0. Loss‐of‐function crk4 mutants in the Col‐0 background were less drought tolerant than Col‐0, whereas overexpressing CRK4 in the Ler‐0 background partially to completely restored the drought‐sensitive phenotype of Ler‐0. F1 plants derived from a cross between the crk4 mutant and Ler‐0 showed an ABA‐insensitive phenotype with respect to stomatal movement, along with reduced drought tolerance like Ler‐0. We demonstrate that CRK4 interacts with the U‐box E3 ligase PUB13 and enhances its abundance, thus promoting the degradation of ABA‐INSENSITIVE 1 (ABI1), a negative regulator of ABA signalling. Together, these findings reveal an important regulatory mechanism for modulating ABI1 levels by the CRK4‐PUB13 module to fine‐tune drought tolerance in Arabidopsis. Summary statement: CRK4, contributing to the drought stress difference between Col‐0 and Ler, interacts with and enhances the protein levels of the U‐box E3 ligase PUB13, which promotes the degradation of ABI1 (ABA‐INSENSITIVE 1), thus positively regulating ABA‐mediated stomatal movements and drought stress tolerance. [ABSTRACT FROM AUTHOR]

Summary: Plant transpiration is controlled by stomata, with S‐ and R‐type anion channels playing key roles in guard cell action. Arabidopsis mutants lacking the ALMT12/QUAC1 R‐type anion channel function in guard cells show only a partial reduction in R‐type channel currents. The molecular nature of these remaining R‐type anion currents is still unclear.To further elucidate this, patch clamp, transcript and gas‐exchange measurements were performed with wild‐type (WT) and different almt mutant plants.The R‐type current fraction in the almt12 mutant exhibited the same voltage dependence, susceptibility to ATP block and lacked a chloride permeability as the WT. Therefore, we asked whether the R‐type anion currents in the ALMT12/QUAC1‐free mutant are caused by additional ALMT isoforms. In WT guard cells, ALMT12, ALMT13 and ALMT14 transcripts were detected, whereas only ALMT13 was found expressed in the almt12 mutant. Substantial R‐type anion currents still remained active in the almt12/13 and almt12/14 double mutants as well as the almt12/13/14 triple mutant. In good agreement, CO2‐triggered stomatal closure required the activity of ALMT12 but not ALMT13 or ALMT14.The results suggest that, with the exception of ALMT12, channel species other than ALMTs carry the guard cell R‐type anion currents. [ABSTRACT FROM AUTHOR]

5-Aminolevulinic acid (ALA), as a new natural plant growth regulator, has been proved to regulate protein phosphatase 2A (PP2A) activity to promote stomatal opening in apple (Malus domestica) leaves. However, the molecular mechanisms underlying remain unclear. Here, we cloned and transformed MdPTPA, MdPP2AC, and MdSnRK2.6 of apple into tobaccos (Nicotiana tabacum) and found that over-expression (OE)-MdPTPA or OE-MdPP2AC promoted stomatal aperture while OE-MdSnRK2.6 induced stomatal closure under normal or drought condition. The Ca2+ and H2O2 levels in the guard cells of OE-MdPTPA and OE-MdPP2AC was decreased but flavonols increased, and the results in OESnRK2.6 was contrary. Exogenous ALA stimulated PP2A activity but depressed SnRK2.6 activity in transgenic tobaccos, leading to less Ca2+, H2O2 and more flavonols in guard cells, and consequently stomatal opening. OE-MdPTPA improved stomatal opening and plant growth but impaired drought tolerance, while OE-MdSnRK2.6 improved drought tolerance but depressed the leaf Pn. Only OE-MdPP2AC improved stomatal opening, leaf Pn, plant growth, as well as drought tolerance. These suggest that the three genes involved in ALAregulating stomatal movement have their respective unique biological functions. Yeast two-hybrid (Y2H) assays showed that MdPP2AC interacted with MdPTPA or MdSnRK2.6, respectively, but no interaction of MdPTPA with MdSnRK2.6 was found. Yeast three-hybrid (Y3H) assay showed that MdPTPA promoted the interactions between MdPP2AC and MdSnRK2.6. Therefore, we propose a regulatory module of PTPA-PP2AC-SnRK2.6 that may be involved in mediating the ALA-inducing stomatal aperture in green plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cotton GhMKK16 is functionally identified to promotes ABA accumulation, and enhances drought tolerance via regulating stomatal closure under drought stress. • GhMKK16 mediated stomatal closure and drought tolerance depend on GhMPK32 or GhEDT1. • GhMKK16 interacts with GhMAP3K62 and GhMPK32 to form a MAPK cascade pathway GhMAP3K62-GhMKK16-GhMPK32. • GhEDT1 was identified as a downstream transcription factor target of MAPK cascade pathway GhMAP3K62-GhMKK16-GhMPK32.GhEDT1 was found to bind to the promoter of GhNCED3 and to activate its expression, resulting in ABA accumulation. • It was proposed that the MAPK cascade GhMAP3K62-GhMKK16-GhMPK32 pathway functions in the cotton drought response through ABA-dependent stomatal movement. Drought is the principal abiotic stress that severely impacts cotton (Gossypium hirsutum) growth and productivity. Upon sensing drought, plants activate stress-related signal transduction pathways, including ABA signal and mitogen-activated protein kinase (MAPK) cascade. However, as the key components with the fewest members in the MAPK cascade, the function and regulation of GhMKKs need to be elucidated. In addition, the relationship between MAPK module and the ABA core signaling pathway remains incompletely understood. Here we aim to elucidate the molecular mechanism of cotton response to drought, with a focus on mitogen-activated protein kinase (MAPK) cascades activating ABA signaling. Biochemical, molecular and genetic analysis were used to study the GhMAP3K62-GhMKK16-GhMPK32-GhEDT1 pathway genes. A nucleus- and membrane-localized MAPK cascade pathway GhMAP3K62-GhMKK16-GhMPK32, which targets and phosphorylates the nuclear-localized transcription factor GhEDT1 , to activate downstream GhNCED3 to mediate ABA-induced stomatal closure and drought response was characterized in cotton. Overexpression of GhMKK16 promotes ABA accumulation, and enhances drought tolerance via regulating stomatal closure under drought stress. Conversely, RNAi-mediated knockdown of GhMKK16 expression inhibits ABA accumulation, and reduces drought tolerance. Virus-induced gene silencing (VIGS)-mediated knockdown of either GhMAP3K62 , GhMPK32 or GhEDT1 expression represses ABA accumulation and reduces drought tolerance through inhibiting stomatal closure. Expression knockdown of GhMPK32 or GhEDT1 in GhMKK16 -overexpressing cotton reinstates ABA content and stomatal opening-dependent drought sensitivity to wild type levels. GhEDT1 could bind to the HD boxes in the promoter of GhNCED3 to activate its expression, resulting in ABA accumulation. We propose that the MAPK cascade GhMAP3K62-GhMKK16-GhMPK32 pathway functions on drought response through ABA-dependent stomatal movement in cotton. [ABSTRACT FROM AUTHOR]

Cucumber (Cucumis sativus L.) is a globally prevalent and extensively cultivated vegetable whose yield is significantly influenced by various abiotic stresses, including drought, heat, and salinity. Transcription factors, such as zinc finger-homeodomain proteins (ZHDs), a plant-specific subgroup of Homeobox, play a crucial regulatory role in stress resistance. In this study, we identified 13 CsZHDs distributed across all six cucumber chromosomes except chromosome 7. Phylogenetic analysis classified these genes into five clades (ZHDI-IV and MIF) with different gene structures but similar conserved motifs. Collinearity analysis revealed that members of clades ZHD III, IV, and MIF experienced amplification through segmental duplication events. Additionally, a closer evolutionary relationship was observed between the ZHDs in Cucumis sativus (C. sativus) and Arabidopsis thaliana (A. thaliana) compared to Oryza sativa (O. sativa). Quantitative real-time PCR (qRT-PCR) analysis demonstrated the general expression of CsZHD genes across all tissues, with notable expression in leaf and flower buds. Moreover, most of the CsZHDs, particularly CsZHD9-11, exhibited varying responses to drought, heat, and salt stresses. Virus-induced gene silencing (VIGS) experiments highlighted the potential functions of CsZHD9 and CsZHD10, suggesting their positive regulation of stomatal movement and responsiveness to drought stress. In summary, these findings provide a valuable resource for future analysis of potential mechanisms underlying CsZHD genes in response to stresses.

Susceptibility of plants to salinity stress is a looming threat to crop productivity worldwide, thereby warranting the strategies to counter stress. We investigated the effects of combined foliar treatment with salicylic acid (SA) and methyl jasmonate (MeJA) on the growth and development of two elite varieties of potato under salinity stress. The salinity stress manifested membrane damage, electrolyte leakage, and production of H2O2 and free radical superoxide anion. Application of SA or MeJA individually could not significantly improve the performance of potato plants exposed to salinity stress. However, treatment with combinations of SA and MeJA synergistically mitigated the adverse effects of salinity, as reflected by reduced membrane damage and electrolyte leakage and lower accumulation of H2O2 and free radical superoxide anion. Moreover, plants treated with the combination treatment had higher relative water content and redox pools of ascorbate and glutathione under salinity stress. The treatment promoted the accumulation of K+ and lowered the Na+ content. SA and MeJA synergistically enhanced the activities of the antioxidant enzymes in the Halliwell-Asada pathway and modulated the photosynthetic and transpiration rates. Overall, our results indicate that the combined foliar treatments with SA and MeJA have positive effects on the growth, development, and yield of potato through maintenance of ion homeostasis and photosynthetic traits. [ABSTRACT FROM AUTHOR]

Significance: Hydrogen sulfide (H2S) is a multitasking potent regulator that facilitates plant growth, development, and responses to environmental stimuli. Recent Advances: The important beneficial effects of H2S in various aspects of plant physiology aroused the interest of this chemical for agriculture. Protein cysteine persulfidation has been recognized as the main reduction–oxidation (redox) regulatory mechanism of H2S signaling. An increasing number of studies, including large-scale proteomic analyses and functional characterizations, have revealed that H2S-mediated persulfidations directly regulate protein functions, altering downstream signaling in plants. To date, the importance of H2S-mediated persulfidation in several abscisic acid signaling-controlling key proteins has been assessed as well as their role in stomatal movements, largely contributing to the understanding of the plant H2S-regulatory mechanism. Critical Issues: The molecular mechanisms of the H2S sensing and transduction in plants remain elusive. The correlations of H2S-mediated persulfidation with other oxidative post-translational modifications of cysteines are still to be explored. Future Directions: Implementation of advanced detection approaches for the spatiotemporal monitoring of H2S levels in cells and the current proteomic profiling strategies for the identification and quantification of the cysteine site-specific persulfidation will provide insight into the H2S signaling in plants. Antioxid. Redox Signal. 39, 40–58. [ABSTRACT FROM AUTHOR]

Summary: Hydrogen sulfide is a signaling molecule in plants that regulates essential biological processes through protein persulfidation. However, little is known about sulfide‐mediated regulation in relation to photorespiration.Here, we performed label‐free quantitative proteomic analysis and observed a high impact on protein persulfidation levels when plants grown under nonphotorespiratory conditions were transferred to air, with 98.7% of the identified proteins being more persulfidated under suppressed photorespiration. Interestingly, a higher level of reactive oxygen species (ROS) was detected under nonphotorespiratory conditions.Analysis of the effect of sulfide on aspects associated with non‐ or photorespiratory growth conditions has demonstrated that it protects plants grown under suppressed photorespiration. Thus, sulfide amends the imbalance of carbon/nitrogen and restores ATP levels to concentrations like those of air‐grown plants; balances the high level of ROS in plants under nonphotorespiratory conditions to reach a cellular redox state similar to that in air‐grown plants; and regulates stomatal closure, to decrease the high guard cell ROS levels and induce stomatal aperture. In this way, sulfide signals the CO2‐dependent stomata movement, in the opposite direction of the established abscisic acid‐dependent movement.Our findings suggest that the high persulfidation level under suppressed photorespiration reveals an essential role of sulfide signaling under these conditions. [ABSTRACT FROM AUTHOR]

Summary: Drought is a major environmental stress that threatens crop production. Therefore, identification of genes involved in drought stress response is of vital importance to decipher the molecular mechanism of stress signal transduction and breed drought tolerance crops, especially for maize.Clade A PP2C phosphatases are core abscisic acid (ABA) signaling components, regulating ABA signal transduction and drought response. However, the roles of other clade PP2Cs in drought resistance remain largely unknown. Here, we discovered a clade F PP2C, ZmPP84, that negatively regulates drought tolerance by screening a transgenic overexpression maize library.Quantitative RT‐PCR indicates that the transcription of ZmPP84 is suppressed by drought stress. We identified that ZmMEK1, a member of the MAPKK family, interacts with ZmPP84 by immunoprecipitation and mass spectrometry analysis. Additionally, we found that ZmPP84 can dephosphorylate ZmMEK1 and repress its kinase activity on the downstream substrate kinase ZmSIMK1, while ZmSIMK1 is able to phosphorylate S‐type anion channel ZmSLAC1 at S146 and T520 in vitro. Mutations of S146 and T520 to phosphomimetic aspartate could activate ZmSLAC1 currents in Xenopus oocytes.Taken together, our study suggests that ZmPP84 is a negative regulator of drought stress response that inhibits stomatal closure through dephosphorylating ZmMEK1, thereby repressing ZmMEK1–ZmSIMK1 signaling pathway. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Salmonella enterica is one of the most common pathogens associated with produce outbreaks worldwide; nonetheless, the mechanisms uncovering their interaction with plants are elusive. Previous reports demonstrate that S. enterica ser. Typhimurium (STm), similar to the phytopathogen Pseudomonas syringae pv. tomato (Pst) DC3000, triggers a transient stomatal closure suggesting its ability to overcome this plant defense and colonize the leaf apoplast. In order to discover new molecular players that function in the stomatal reopening by STm and Pst DC3000, we performed an Arabidopsis mutant screening using thermal imaging. Further stomatal bioassay confirmed that the mutant plants exo70h4-3, sce1-3, bbe8, stp1, and lsu2 have smaller stomatal aperture widths than the wild type Col-0 in response to STm 14028s. The mutants bbe8, stp1 and lsu2 have impaired stomatal movement in response to Pst DC3000. These findings indicate that EXO70H4 and SCE1 are involved in bacterial-specific responses, while BBE8, STP1, and LSU2 may be required for stomatal response to a broad range of bacteria. The identification of new molecular components of the guard cell movement induced by bacteria will enable a better understanding of the initial stages of plant colonization and facilitate targeted prevention of leaf contamination with harmful pathogens.

Abstract Stomata are a pivotal adaptation of land plants and control gas exchange. While most plants present solitary stomata, some plant species experiencing chronic water deficiency display clustered stomata on their epidermis; for instance, limestone‐grown begonias. Moreover, the membrane receptor TOO MANY MOUTHS (TMM) plays a major role in spacing stomata on the epidermis in Arabidopsis, but the function of its Begonia orthologs is unknown. We used two Asian begonias, Begonia formosana (single stomata) and B. hernandioides (clustered stomata), to explore the physiological function of stomatal clustering. We also introduced the Begonia TMMs into Arabidopsis tmm mutants to study the function of Begonia TMMs. B. hernandioides showed higher water use efficiency under high light intensity, smaller stomata, and faster pore opening than B. formosana. The short distance between stomata in a cluster may facilitate cell‐to‐cell interactions to achieve synchronicity in stomatal movement. Begonia TMMs function similarly to Arabidopsis TMM to inhibit stomatal formation, although complementation by TMM from the clustered species was only partial. Stomatal clustering in begonias may represent a developmental strategy to build small and closer stomata to achieve fast responses to light which provides tight support between stomatal development and environmental adaption.

Summary: Glutaredoxins (GRXs) are essential for reactive oxygen species (ROS) homeostasis in responses of plants to environment changes. We previously identified several drought‐responsive CC‐type GRXs in cassava, an important tropical crop. However, how CC‐type GRX regulates ROS homeostasis of cassava under drought stress remained largely unknown. Here, we report that a drought‐responsive CC‐type GRX, namely MeGRXC3, was associated with activity of catalase in the leaves of 100 cultivars (or unique unnamed genotypes) of cassava under drought stress. MeGRXC3 negatively regulated drought tolerance by modulating drought‐ and abscisic acid‐induced stomatal closure in transgenic cassava. It antagonistically regulated hydrogen peroxide (H2O2) accumulation in epidermal cells and guard cells. Moreover, MeGRXC3 interacted with two catalases of cassava, MeCAT1 and MeCAT2, and regulated their activity in vivo. Additionally, MeGRXC3 interacts with a cassava TGA transcription factor, MeTGA2, in the nucleus, and regulates the expression of MeCAT7 through a MeTGA2‐MeMYB63 pathway. Overall, we demonstrated the roles of MeGRXC3 in regulating activity of catalase at both transcriptional and post‐translational levels, therefore involving in ROS homeostasis and stomatal movement in responses of cassava to drought stress. Our study provides the first insights into how MeGRXC3 may be used in molecular breeding of cassava crops. [ABSTRACT FROM AUTHOR]

[Display omitted] • GhTULP30 transcription in cotton was induced by drought and salt stress. • Ectopic GhTULP30 expression significantly improved yeast cell tolerance to drought and salt. • GhTULP30 overexpression increased the tolerance of Arabidopsis to drought and salt stress. • Silencing GhTULP30 affected stomatal movement and decreased tolerance to drought stress. • Protein experiments exhibited the interaction of GhTULP30 with GhSKP1B and GhXERICO. Cotton is a vital industrial crop that is gradually shifting to planting in arid areas. However, tubby-like proteins (TULPs) involved in plant response to various stresses are rarely reported in cotton. The present study exhibited that GhTULP30 transcription in cotton was induced by drought stress. The present study demonstrated the improvement of plant tolerance to drought stress by GhTULP30 through regulation of stomatal movement. GhTULP30 response to drought and salt stress was preliminarily confirmed by qRT-PCR and yeast stress experiments. Ectopic expression in Arabidopsis and endogenous gene silencing in cotton were used to determine stomatal movement. Yeast two-hybrid and spilt-luciferase were used to screen the interacting proteins. Ectopic expression of GhTULP30 in yeast markedly improved yeast cell tolerance to salt and drought. Overexpression of GhTULP30 made Arabidopsis seeds more resistant to drought and salt stress during seed germination and increased the stomata closing speed of the plant under drought stress conditions. Silencing of GhTULP30 in cotton by virus-induced gene silencing (VIGS) technology slowed down the closure speed of stomata under drought stress and decreased the length and width of the stomata. The trypan blue and diaminobenzidine staining exhibited the severity of leaf cell necrosis of GhTULP30 -silenced plants. Additionally, the contents of proline, malondialdehyde, and catalase of GhTULP30 -silenced plants exhibited significant variations, with obvious leaf wilting. Protein interaction experiments exhibited the interaction of GhTULP30 with GhSKP1B and GhXERICO. GhTULP30 participates in plant response to drought stress. The present study provides a reference and direction for further exploration of TULP functions in cotton plants. [ABSTRACT FROM AUTHOR]

With abnormal global climate change and the frequent occurrence of extreme weather, low-temperature stress poses an increasingly serious threat to the diversity of plants. Low temperatures accompanied by limitations in nitrogen cause a series of morphological, physiological, and molecular changes in plants. Nitrogen dioxide (NO 2) is a gas that is considered to be a toxic air pollutant. However, NO 2 in the atmosphere can be absorbed by plants and participate in nitrogen metabolism. In this study, tobacco (Nicotiana tabacum L.) seedlings were fumigated with a concentration of 4 µL·L−1 NO 2 at 4 ℃ for 10 days. NO 2 promoted the glutamine synthetase-glutamate synthase (GS/GOGAT) pathway in the leaves at low temperatures, which transforms more organic nitrogen that can be directly utilized by the plants, and improves the skeleton for carbon metabolism. Moreover, gamma-aminobutyric acid (GABA) was generated through the ornithine and glutamate pathways, and the biosynthesis of proline was also enhanced after treatment with NO 2. Together, these compounds regulate the osmotic balance of tobacco leaf cells under low-temperature stress. NO 2 activated the ascorbate-glutathione (AsA-GSH) cycle in the leaves under low-temperature stress, and this antioxidant enzyme system synergistically removed the intracellular free radicals that result from reactive oxygen species. Additionally, NO 2 significantly increased the content of nitric oxide (NO) in the leaves under low-temperature stress and enhanced the opening of stomata, thus, improving photosynthesis in the leaves. The biosynthesis of chlorophyll in the leaves was inhibited by low-temperature stress, but NO 2 promotes the biosynthesis of chlorophyll directly or through the nitric acid signaling pathway and improves the ability of plants to capture light energy. NO 2 also alleviates the photoinhibition induced by cold stress by regulating photosynthetic electron transfer and absorbing more energy for the assimilation of photosynthetic carbon. This improves the photochemical efficiency of tobacco leaves. In conclusion, NO 2 enhanced the tolerance of tobacco seedlings to low temperature by regulating nitrogen metabolism, the osmotic balance, antioxidant system, and photosynthesis. [Display omitted] • NO 2 promotes stomatal opening and chlorophyll synthesis to enhance the photosynthetic function. • NO 2 promotes the GS/GOGAT cycle in leaves at low temperatures and enhances N metabolism ability. • NO 2 regulates the osmotic balance of tobacco leaf cells under low temperature stress. • NO 2 activates the non-enzymatic antioxidant system in tobacco leaves under low temperature stress [ABSTRACT FROM AUTHOR]

Increases in CO2 concentration in plant leaves due to respiration in the dark and the continuing atmospheric [CO2] rise cause closing of stomatal pores, thus affecting plant-water relations globally. However, the underlying CO2/bicarbonate (CO2/HCO3-) sensing mechanisms remain unknown. [CO2] elevation in leaves triggers stomatal closure by anion efflux mediated via the SLAC1 anion channel localized in the plasma membrane of guard cells. Previous reconstitution analysis has suggested that intracellular bicarbonate ions might directly up-regulate SLAC1 channel activity. However, whether such a CO2/HCO3- regulation of SLAC1 is relevant for CO2 control of stomatal movements in planta remains unknown. Here, we computationally probe for candidate bicarbonate-interacting sites within the SLAC1 anion channel via long-timescale Gaussian accelerated molecular dynamics (GaMD) simulations. Mutations of two putative bicarbonate-interacting residues, R256 and R321, impaired the enhancement of the SLAC1 anion channel activity by CO2/HCO3- in Xenopus oocytes. Mutations of the neighboring charged amino acid K255 and residue R432 and the predicted gate residue F450 did not affect HCO3- regulation of SLAC1. Notably, gas-exchange experiments with slac1-transformed plants expressing mutated SLAC1 proteins revealed that the SLAC1 residue R256 is required for CO2 regulation of stomatal movements in planta, but not for abscisic acid (ABA)-induced stomatal closing. Patch clamp analyses of guard cells show that activation of S-type anion channels by CO2/HCO3-, but not by ABA, was impaired, indicating the relevance of R256 for CO2 signal transduction. Together, these analyses suggest that the SLAC1 anion channel is one of the physiologically relevant CO2/HCO3- sensors in guard cells.

SUMMARY: Drought is a major environmental factor that limits the production of alfalfa (Medicago sativa). In the present study, M. sativa NUCLEAR TRANSPORT FACTOR 2‐LIKE (MsNTF2L) was identified as a nucleus‐, cytoplasm‐, and plasma membrane‐localized protein. Its transcriptional expression was highly induced by ABA and drought stress. Overexpression of MsNTF2L in Arabidopsis resulted in hypersensitivity to ABA during both the seed germination and seedling growth stages. However, transgenic Arabidopsis plants exhibited enhanced tolerance to drought stress by reducing the levels of reactive oxygen species (ROS) and increasing the expression of stress/ABA‐inducible genes. Consistently, analysis of MsNTF2L overexpression (OE) and RNA interference (RNAi) alfalfa plants revealed that MsNTF2L confers drought tolerance through promoting ROS scavenging, a decrease in stomatal density, ABA‐induced stomatal closure, and epicuticular wax crystal accumulation. MsNTF2L highly affected epicuticular wax deposition, as a large group of wax biosynthesis and transport genes were influenced in the alfalfa OE and RNAi lines. Furthermore, transcript profiling of drought‐treated alfalfa WT, OE, and RNAi plants showed a differential drought response for genes related to stress/ABA signaling, antioxidant defense, and photosynthesis. Taken together, these results reveal that MsNTF2L confers drought tolerance in alfalfa via modulation of leaf water loss (by regulating both stomata and wax deposition), antioxidant defense, and photosynthesis. Significance Statement: By studying the drought‐inducible genes of alfalfa (Medicago sativa), we discovered that the nucleus‐, cytoplasm‐, and plasma membrane‐localized protein NUCLEAR TRANSPORT FACTOR 2‐LIKE improves drought tolerance by modulating leaf water loss (by regulating both stomata and wax deposition), antioxidant defense, and photosynthesis. This gene might be targeted in future breeding programs to improve drought tolerance in alfalfa. [ABSTRACT FROM AUTHOR]

There are numerous studies on enhancing plant resistance to stress using melatonin, but few studies about its effect on photosynthesis. Herein, we summarized the role of melatonin in photosynthesis. Melatonin regulates chlorophyll synthesis and degradation through the transcription of related genes and hormone signals. It protects photosynthetic proteins and maintains the photosynthetic process through improving the transcription of photosystem genes, activating the antioxidant system, and promoting the xanthophyll cycle. Melatonin potentially regulates plant stomatal movement through CAND2/PMTR1. Finally, it controls the photosynthetic carbon cycle by regulating the metabolism of sugar, the gluconeogenesis pathway, and the degradation and transport of transient starch. [ABSTRACT FROM AUTHOR]

Calcium-dependent protein kinases (CDPKs/CPKs) are members of the Ca 2+ -sensitive Ser/Thr protein kinase family and play a crucial role in plant growth and development and responses to abiotic stress. CDPKs are capable of rapidly sensing changes in intracellular Ca 2+ signals and recognizing and phosphorylating specific substrates, thereby transmitting and amplifying Ca 2+ signal cascades downstream. They are involved in plant responses to stress conditions such as drought, saline-alkali stress, and injuries and regulate plant growth and development, gene expression, ion channel activity, and stomatal movement. The autophosphorylation of CDPKs can affect their activities and substrate specificity. CDPKs have the ability to bind to and phosphorylate multiple substrates. In addition to participating in respiratory burst oxidase homolog (RBOH), mitogen-activated protein kinase (MAPK), and plant hormone signaling pathways, CDPKs can also bind to 14-3-3 proteins, which enables the regulation of plant responses to stress and promotes plant growth and development. This paper summarized the research findings on the discovery, structure, classification, and roles of CDPKs in plant responses to stress and proposed the future research directions, aiming to provide the genetic resources and a theoretical basis for improving the stress tolerance of crops.

Transient stimulus-specific increases in the cytosolic Ca 2+ concentration ("calcium signatures") of guard cells have been proposed to regulate the opening and closure of stomatal pores on plant leaves. However, the mechanism by which these Ca 2+ signatures are generated and translated into stomatal movement is still largely unresolved. We used a light-gated, Ca 2+ -permeable variant of ChannelRhodopsin 2 (ChR2-XXM2.0) that was stimulated by tailored light pulses to investigate this phenomenon. We found that activation of the ChR2-XXM2.0 channel provoked characteristic increases in the cytosolic concentration of Ca 2+ . We also demonstrated that the endoplasmic reticulum (ER) was involved in the generation of these calcium signatures. Using ChR2-XXM2.0 technology, we showed that transient increases in Ca 2+ activated S-type anion channels and determined the extent and speed of stomatal closure with their number and frequency. Our data reveal that guard cells are capable of counting Ca 2+ transients in order to optimize stomatal aperture in the prevailing environmental conditions., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Stomata are a pivotal adaptation of land plants and control gas exchange. While most plants present solitary stomata, some plant species experiencing chronic water deficiency display clustered stomata on their epidermis; for instance, limestone‐grown begonias. Moreover, the membrane receptor TOO MANY MOUTHS (TMM) plays a major role in spacing stomata on the epidermis in Arabidopsis, but the function of its Begonia orthologs is unknown. We used two Asian begonias, Begonia formosana (single stomata) and B. hernandioides (clustered stomata), to explore the physiological function of stomatal clustering. We also introduced the Begonia TMMs into Arabidopsis tmm mutants to study the function of Begonia TMMs. B. hernandioides showed higher water use efficiency under high light intensity, smaller stomata, and faster pore opening than B. formosana. The short distance between stomata in a cluster may facilitate cell‐to‐cell interactions to achieve synchronicity in stomatal movement. Begonia TMMs function similarly to Arabidopsis TMM to inhibit stomatal formation, although complementation by TMM from the clustered species was only partial. Stomatal clustering in begonias may represent a developmental strategy to build small and closer stomata to achieve fast responses to light which provides tight support between stomatal development and environmental adaption. [ABSTRACT FROM AUTHOR]

SUMMARY: The phytohormone abscisic acid (ABA) regulates ion channel activity and stomatal movement in response to drought stress. Cellular ABA levels change depending on cellular and environmental conditions via modulation of its biosynthesis, catabolism and transport. Although factors involved in ABA biosynthesis and degradation have been studied extensively, how ABA transporters are modulated to fine‐tune ABA levels, especially under drought stress, remains elusive. Here, we show that Arabidopsis thaliana SORTING NEXIN 2 (SNX2) proteins play a critical role in endosomal trafficking of the ABA exporter ATP BINDING CASETTE G25 (ABCG25) via direct interaction at endosomes, leading to its degradation in the vacuole. In agreement, snx2a and snx2b mutant plants showed enhanced recycling of GFP‐ABCG25 from early endosomes to the plasma membrane and higher accumulation of GFP‐ABCG25. Phenotypically, snx2a and snx2b plants were highly sensitive to exogenous ABA and displayed enhanced ABA‐mediated inhibition of inward K+ currents and ABA‐mediated activation of slow anion currents in guard cells, resulting in an increased tolerance to drought stress. Based on these results, we propose that SNX2 proteins play a crucial role in stomatal movement and tolerance to drought stress by modulating the endosomal trafficking of ABCG25 and thus cellular ABA levels. Significance Statement: Increasing evidence supports a role for sorting nexins (SNXs) in intracellular trafficking of membrane proteins; however, the role of SNX2 proteins in endomembrane protein trafficking remains elusive, and it is not clear whether and how they might function in response to abiotic stress. Here, we show that Arabidopsis SNX2a and SNX2b play a crucial role in stomatal movement and tolerance to drought stress via direct interaction with the abscisic acid exporter ABCG25 and modulation of its endosomal trafficking. [ABSTRACT FROM AUTHOR]

The calcium-sensing receptor (CAS), as a chloroplast thylakoid membrane protein, is involved in the process of external Ca2+-induced cytosolic Ca2+ increase in plants. However, the underlying mechanism regulating this process is lacking. Furthermore, recent evidence suggests that CAS may perform additional roles in plants. Here, we provided an update covering the multiple roles of CAS in stomatal movement regulation and Ca2+ signaling in plants. We also analyzed the possible phosphorylation mechanism of CAS by light and discuss the role of CAS in abiotic stress (drought, salt stress) and biotic stresses (plant immune signaling). Finally, we proposed a perspective for future experiments that are required to fill gaps in our understanding of the biological function of CAS in plants. • Calcium-sensing receptor (CAS) is a photoregulated phosphorylated protein located on chloroplast thylakoid membrane. • CAS involved in the process of external Ca2+-induced cytosolic Ca2+ increase in plants. • CAS involved in light signal transduction, stomatal movement regulation and drought tolerance. • CAS-modulated MAPK signaling involved plastid-nucleus communication. • CAS-modulated SA signaling mediated plant immune signaling. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO2) has long been viewed as toxic gas and air pollutant, but now is being verified as a signaling molecule in mammalian cells. SO2 can be endogenously produced and rapidly transformed into sulfur-containing compounds (e.g., hydrogen sulfide, cysteine, methionine, glutathione, glucosinolate, and phytochelatin) to maintain its homeostasis in plant cells. Exogenous application of SO2 in the form of gas or solution can trigger the expression of thousands of genes. The physiological functions of these genes are involved in the antioxidant defense, osmotic adjustment, and synthesis of stress proteins, secondary metabolites, and plant hormones, thus modulating numerous plant physiological processes. The modulated physiological processes by SO2 are implicated in seed germination, stomatal action, postharvest physiology, and plant response to environmental stresses. However, the review on the signaling role of SO2 in plants is little. In this review, the anabolism and catabolism of SO2 in plants were summarized. In addition, the signaling role of SO2 in seed germination, stomatal movement, fruit fresh-keeping, and plant response to environmental stresses (including drought, cold, heavy metal, and pathogen stresses) was discussed. Finally, the research direction of SO2 in plants is also proposed. [ABSTRACT FROM AUTHOR]

Sulfur, widely present in the soil and atmosphere, is one of the essential elements for plants. Sulfate is a dominant form of sulfur in soils taken up by plant roots. In addition to the assimilation into sulfur compounds essential for plant growth and development, it has been reported recently that sulfate as well as other sulfur containing compounds can also induce stomatal movement. Here, we first summarized the uptake and transport of sulfate and atmospheric sulfur, including H2O and SO2, and then, focused on the effects of inorganic and organic sulfur on stomatal movement. We concluded all the transporters for different sulfur compounds, and compared the expression level of those transporters in guard cells and mesophyll cells. The relationship between abscisic acid and sulfur compounds in regulation of stomatal movement were also discussed. [ABSTRACT FROM AUTHOR]

Stomatal movements are essential for plants to regulate photosynthesis rate, water status, and immunity. Upon stress stimulation, the production of hydrogen peroxide (H 2 O 2) in the apoplasts and its accumulation within the guard cells are among key determinatives for stomatal closure. The regulatory mechanisms of H 2 O 2 production and transport under plant–pathogen interaction and drought stress response in stomata are important fields of research. Specifically, the regulation of NADPH oxidases and aquaporins appears to be crucial in H 2 O 2 -controlled stomatal closure. In this review, we summarize how the calcium-dependent and calcium-independent mechanisms activate RESPIRATORY BURST OXIDASE HOMOLOG (RBOH)D/F NADPH oxidases and the aquaporin PIP2;1 to induce stomatal closure, and highlight how the H 2 O 2 production is targeted by pathogen toxins and effectors to counteract plant immunity. Stomatal opening and closure are essential for plants to regulate photosynthesis rate, water status, and immunity. Stress-induced H 2 O 2 burst in apoplasts and its accumulation within the guard cells have a central role in inducing stomatal closure. H 2 O 2 production by NADPH oxidases and its transport by aquaporins are crucial points in regulating stomatal closure in response to drought and pathogen stresses. Pathogens target the accumulation of H 2 O 2 and counteract plant stomatal closure in immunity. Manipulation of the H 2 O 2 signaling improves drought tolerance through increased stomata closure. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO2) has long been viewed as toxic gas and air pollutant, but now is being verified as a signaling molecule in mammalian cells. SO2 can be endogenously produced and rapidly transformed into sulfur-containing compounds (e.g., hydrogen sulfide, cysteine, methionine, glutathione, glucosinolate, and phytochelatin) to maintain its homeostasis in plant cells. Exogenous application of SO2 in the form of gas or solution can trigger the expression of thousands of genes. The physiological functions of these genes are involved in the antioxidant defense, osmotic adjustment, and synthesis of stress proteins, secondary metabolites, and plant hormones, thus modulating numerous plant physiological processes. The modulated physiological processes by SO2 are implicated in seed germination, stomatal action, postharvest physiology, and plant response to environmental stresses. However, the review on the signaling role of SO2 in plants is little. In this review, the anabolism and catabolism of SO2 in plants were summarized. In addition, the signaling role of SO2 in seed germination, stomatal movement, fruit fresh-keeping, and plant response to environmental stresses (including drought, cold, heavy metal, and pathogen stresses) was discussed. Finally, the research direction of SO2 in plants is also proposed.

Sulfur, widely present in the soil and atmosphere, is one of the essential elements for plants. Sulfate is a dominant form of sulfur in soils taken up by plant roots. In addition to the assimilation into sulfur compounds essential for plant growth and development, it has been reported recently that sulfate as well as other sulfur containing compounds can also induce stomatal movement. Here, we first summarized the uptake and transport of sulfate and atmospheric sulfur, including H2O and SO2, and then, focused on the effects of inorganic and organic sulfur on stomatal movement. We concluded all the transporters for different sulfur compounds, and compared the expression level of those transporters in guard cells and mesophyll cells. The relationship between abscisic acid and sulfur compounds in regulation of stomatal movement were also discussed.

Stomata are specialized epidermal structures composed of two guard cells and are involved in gas and water exchange between plants and the environment and pathogen entry into the plant interior. Stomatal movement is a response to many internal and external stimuli to increase adaptability to environmental change. The cytoskeleton, including actin filaments and microtubules, is highly dynamic in guard cells during stomatal movement, and the destruction of the cytoskeleton interferes with stomatal movement. In this review, we discuss recent progress on the organization and dynamics of actin filaments and microtubule network in guard cells, and we pay special attention to cytoskeletal-associated protein-mediated cytoskeletal rearrangements during stomatal movement. We also discuss the potential mechanisms of stomatal movement in relation to the cytoskeleton and attempt to provide a foundation for further research in this field. [ABSTRACT FROM AUTHOR]

We studied the allelopathic stress of C. ambrosioides volatile oil using the epidermal strip bioassay, microscopy and histochemical techniques on stomatal movement in leaves from broad beans (Vicia faba L.), peanuts (Arachis hypogaea L.) and peas (Pisum sativum L.). We also studied the changes in vacuoles, microfilaments and signalling molecules ROS, NO and Ca2+ in guard cells. The stomatal aperture of 3-test legume species decreased significantly (P < 0.05) in volatile oil concentration-dependent manner. Compared with control, the applied volatile oil increased the numbers of vacuoles but decreased their volume in guard cells of all 3-test crops. Aggregation of microfilament skeletons, increased the in ROS, NO and Ca2+ concentrations. These effects could be alleviated, when related inhibitors (Cytochalasin B, AS, LaCl3 and L-NAME) were used with volatile oil. It is speculated that the dynamic changes in guard cell microfilaments caused by volatile oil of C. ambrosioides could lead to increased ROS and NO levels by activating the related enzymes, which increased the cytoplasmic free Ca2+ levels in guard cells. Thereby the ion channels in plasma membrane and vacuolar membrane were affected. The bigger vacuoles in guard cells were divided into smaller ones, turgor pressure was decreased and stomata were closed. The stomatal movement of broad bean was most sensitive to volatile oil of C. ambrosioides, which showed strong allelopathy. [ABSTRACT FROM AUTHOR]

Essential macronutrient potassium (K) and environmental signal light regulate a number of vital plant biological processes related to growth, development, and stress response. Recent research has shown connections between the perception of light and the regulation of K in plants. Photoreceptors-mediated wavelength-specific light perception activates signaling cascades which mediate stomatal movement by altering K+influx/efflux via K+ channels in the guard cells. The quality, intensity, and duration of light affect the regulation of K nutrition and crop quality. Blue/red illumination or red combined blue light treatment increases the expression levels of K transporter genes, K uptake and accumulation, leading to increased lycopene synthesis and improved fruit color in tomato. Despite the commonalities of light and K in multiple functions, our understanding of light regulation of K and associated physiological and molecular processes is fragmentary. In this review, we take a look at the light-controlled K uptake and utilization in plants and propose working models to show potential mechanisms. We discuss major light signaling components, their possible involvement in K nutrition, stomatal movement and crop quality by linking the perception of light signal and subsequent regulation of K. We also pose some outstanding questions to guide future research. Our analysis suggests that the enhancement of K utilization efficiency by manipulation of light quality and light signaling components can be a promising strategy for K management in crop production. • Light quality, intensity and duration affect K uptake, accumulation and crop quality. • Blue and red light signals merge to induce stomatal opening by K+influx in guard cell. • Light induces lycopene synthesis in tomatoes by modulating HAK expression in roots. • Photoreceptors coordinately function to regulate K uptake and accumulation in plants. • K utilization efficiency can be enhanced by manipulating light singling components. [ABSTRACT FROM AUTHOR]

Drought and salt are two major abiotic stresses that severely impact plant growth and development, as well as crop production. A previous study showed that OsOSCA1.4, one of eleven rice OSCAs (OsOSCAs), complements hyperosmolality-induced [Ca2+]cyt increases (OICIcyt), salt stress-induced [Ca2+]cyt increases (SICIcyt) and the associated growth phenotype in Arabidopsis osca1 (reduced hyperosmolality-induced [Ca2+]cyt increase 1). In this study, Except for OsOSCA2.3 and OsOSCA4.1, we generated independent transgenic lines overexpressing eight other OsOSCAs in the osca1 to explore their functions in osmotic Ca2+ signalling, stomatal movement, leaf water loss, and root growth in response to hyperosmolality and salt stress. Similar to OsOSCA1.4, overexpression of OsOSCA1.1 or OsOSCA2.2 in osca1 complemented OICIcyt and SICIcyt, as well as stomatal closure and root growth in response to hyperosmolality and salt stress treatments, and drought-related leaf water loss. In addition, overexpression of OsOSCA1.2, OsOSCA1.3 or OsOSCA2.1 in osca1 restored OICIcyt and SICIcyt, whereas overexpression of OsOSCA2.5 or OsOSCA3.1 did not. Moreover, osca1 overexpressing these five OsOSCAs exhibited various abiotic stress-associated growth phenotypes. However, overexpression of OsOSCA2.4 did not have any of these effects. These results indicated that multiple members of the OsOSCA family have redundant functions in osmotic sensing and diverse roles in stress adaption. [ABSTRACT FROM AUTHOR]