Zahra Kahrizi, Christos Michailidis, Karel Raabe, Vinod Kumar, David Honys, Said Hafidh
Pollen germination and pollen tube (PT) growth are extremely sensitive to high temperatures. During heat stress (HS), global translation shuts down and favors the maintenance of the essential cellular proteome for cell viability and protection against protein misfolding. Here, we demonstrate that under normal conditions, the Arabidopsis (Arabidopsis thaliana) eukaryotic translation initiation factor subunit eif3m1/eif3m2 double mutant exhibits poor pollen germination, loss of PT integrity and an increased rate of aborted seeds. Surprisingly, under HS at 37 °C, eif3m1 pollen germination outperformed wild-type Col-0, showing enhanced PT integrity. We established that the improved thermotolerance of the eif3m1 PT was due to increased expression of its putative paralog eIF3M2, which in turn upregulated Heat Shock protein 70 (HSP70) mRNA and protein levels. Indeed, eIF3M2 overexpression upregulated HSP70 expression, whereas eif3m2 knockdown showed reduced HSP70.1 promoter activity and increased in PT burst under HS conditions. Moreover, we show that eIF3M2 coimmunoprecipitates with HSP70 in PTs and directly interacts with cytoplasmic HSP70.1/2/4 and eIF4G in Nicotiana benthamiana pavement cells. Collectively, our data revealed that plants employ the eIF3M2-HSP70 module as a regulator of thermotolerance to maintain PT membrane integrity and improve fertilization and seed set adaptation under high temperatures.
{"title":"The translation initiation factor eIF3M2 upregulates HEAT SHOCK PROTEIN 70 to maintain pollen tube membrane integrity during heat shock","authors":"Zahra Kahrizi, Christos Michailidis, Karel Raabe, Vinod Kumar, David Honys, Said Hafidh","doi":"10.1093/plphys/kiae643","DOIUrl":"https://doi.org/10.1093/plphys/kiae643","url":null,"abstract":"Pollen germination and pollen tube (PT) growth are extremely sensitive to high temperatures. During heat stress (HS), global translation shuts down and favors the maintenance of the essential cellular proteome for cell viability and protection against protein misfolding. Here, we demonstrate that under normal conditions, the Arabidopsis (Arabidopsis thaliana) eukaryotic translation initiation factor subunit eif3m1/eif3m2 double mutant exhibits poor pollen germination, loss of PT integrity and an increased rate of aborted seeds. Surprisingly, under HS at 37 °C, eif3m1 pollen germination outperformed wild-type Col-0, showing enhanced PT integrity. We established that the improved thermotolerance of the eif3m1 PT was due to increased expression of its putative paralog eIF3M2, which in turn upregulated Heat Shock protein 70 (HSP70) mRNA and protein levels. Indeed, eIF3M2 overexpression upregulated HSP70 expression, whereas eif3m2 knockdown showed reduced HSP70.1 promoter activity and increased in PT burst under HS conditions. Moreover, we show that eIF3M2 coimmunoprecipitates with HSP70 in PTs and directly interacts with cytoplasmic HSP70.1/2/4 and eIF4G in Nicotiana benthamiana pavement cells. Collectively, our data revealed that plants employ the eIF3M2-HSP70 module as a regulator of thermotolerance to maintain PT membrane integrity and improve fertilization and seed set adaptation under high temperatures.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"15 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143030734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fernanda A L Silva-Alvim, Jonas Chaves Alvim, Julian M Hibberd, Andrew R Harvey, Michael R Blatt
Accelerating stomatal kinetics through synthetic optogenetics and mutations that enhance guard cell K+ flux has proven a viable strategy to improve water use efficiency and biomass production. Stomata of the model C4 species Gynandropsis gynandra, a relative of the C3 plant Arabidopsis thaliana, are similarly fast to open and close. We identified and cloned the guard cell rectifying outward K+ channel (GROK) of Gynandropsis and showed that GROK is preferentially expressed in stomatal guard cells. GROK is homologous to the Arabidopsis guard cell K+ channel GORK and, expressed in oocytes, yields a K+ current consistent with that of Gynandropsis guard cells. Complementing the Arabidopsis gork mutant with GROK promoted K+ channel gating and K+ flux, increasing stomatal kinetics and yielding gains in water use efficiency and biomass with varying light, especially under water limitation. Our findings demonstrate the potential for engineering a C4 K+ channel into guard cells of a C3 species and they speak to the puzzle of how C4 species have evolved mechanisms that enhance water use efficiency and growth under stress.
{"title":"A C4 plant K+ channel accelerates stomata to enhance C3 photosynthesis and water use efficiency","authors":"Fernanda A L Silva-Alvim, Jonas Chaves Alvim, Julian M Hibberd, Andrew R Harvey, Michael R Blatt","doi":"10.1093/plphys/kiaf039","DOIUrl":"https://doi.org/10.1093/plphys/kiaf039","url":null,"abstract":"Accelerating stomatal kinetics through synthetic optogenetics and mutations that enhance guard cell K+ flux has proven a viable strategy to improve water use efficiency and biomass production. Stomata of the model C4 species Gynandropsis gynandra, a relative of the C3 plant Arabidopsis thaliana, are similarly fast to open and close. We identified and cloned the guard cell rectifying outward K+ channel (GROK) of Gynandropsis and showed that GROK is preferentially expressed in stomatal guard cells. GROK is homologous to the Arabidopsis guard cell K+ channel GORK and, expressed in oocytes, yields a K+ current consistent with that of Gynandropsis guard cells. Complementing the Arabidopsis gork mutant with GROK promoted K+ channel gating and K+ flux, increasing stomatal kinetics and yielding gains in water use efficiency and biomass with varying light, especially under water limitation. Our findings demonstrate the potential for engineering a C4 K+ channel into guard cells of a C3 species and they speak to the puzzle of how C4 species have evolved mechanisms that enhance water use efficiency and growth under stress.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"22 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143030736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kiwifruit bacterial canker, a highly destructive disease caused by Pseudomonas syringae pv. actinidiae (Psa), seriously affects kiwifruit (Actinidia spp.) production. Lignin deposition in infected cells serves as a defense mechanism, effectively suppressing pathogen growth. However, the underlying process remains unclear. In this study, we determined that Psa infection leads to a significant increase in S-lignin accumulation in kiwifruit. The S/G ratio in lignin was higher in a Psa-resistant cultivar than in a Psa-sensitive cultivar. Furthermore, kiwifruit laccase 35 (AcLac35), encoding an enzyme in the lignin biosynthesis pathway with characteristic laccase activity, showed tissue-specific expression in plants and was upregulated following infection by Psa. Overexpressing AcLac35 in kiwifruit leaves resulted in greater lignin content than in wild-type leaves, leading to the formation of thicker cell walls, and also activated plant-pathogen interactions and MAPK pathways, thereby enhancing resistance against Psa infection. Yeast one-hybrid assays, dual-LUC reporter assays, electrophoretic mobility shift assays, and transient injection experiments indicated that SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 9 (AcSPL9) can bind to the AcLac35 promoter, thereby positively regulating its expression. Moreover, overexpression of AcSPL9 increased lignin accumulation in kiwifruit leaves, enhancing resistance to Psa, while virus-induced gene silencing of AcSPL9 expression reduced this resistance. Our findings reveal the function of AsSPL9-AcLac35 in kiwifruit, providing insight into enhancing resistance against Psa in kiwifruit.
{"title":"LACCASE35 Enhances Lignification and Resistance Against Pseudomonas syringae pv. actinidiae Infection in Kiwifruit","authors":"Yawei Li, Dongle Zhang, Xiaojie Wang, Fuxi Bai, Rui Li, Rongrong Zhou, Shunyuan Wu, Zemin Fang, Wei Liu, Lili Huang, Pu Liu","doi":"10.1093/plphys/kiaf040","DOIUrl":"https://doi.org/10.1093/plphys/kiaf040","url":null,"abstract":"Kiwifruit bacterial canker, a highly destructive disease caused by Pseudomonas syringae pv. actinidiae (Psa), seriously affects kiwifruit (Actinidia spp.) production. Lignin deposition in infected cells serves as a defense mechanism, effectively suppressing pathogen growth. However, the underlying process remains unclear. In this study, we determined that Psa infection leads to a significant increase in S-lignin accumulation in kiwifruit. The S/G ratio in lignin was higher in a Psa-resistant cultivar than in a Psa-sensitive cultivar. Furthermore, kiwifruit laccase 35 (AcLac35), encoding an enzyme in the lignin biosynthesis pathway with characteristic laccase activity, showed tissue-specific expression in plants and was upregulated following infection by Psa. Overexpressing AcLac35 in kiwifruit leaves resulted in greater lignin content than in wild-type leaves, leading to the formation of thicker cell walls, and also activated plant-pathogen interactions and MAPK pathways, thereby enhancing resistance against Psa infection. Yeast one-hybrid assays, dual-LUC reporter assays, electrophoretic mobility shift assays, and transient injection experiments indicated that SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 9 (AcSPL9) can bind to the AcLac35 promoter, thereby positively regulating its expression. Moreover, overexpression of AcSPL9 increased lignin accumulation in kiwifruit leaves, enhancing resistance to Psa, while virus-induced gene silencing of AcSPL9 expression reduced this resistance. Our findings reveal the function of AsSPL9-AcLac35 in kiwifruit, providing insight into enhancing resistance against Psa in kiwifruit.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"113 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143030732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yanying Wu, Kaikai Zhu, Si Chen, Enzhen Xing, Jiajia Li, Wenqi Tian, Ming Gao, Jiaxin Kong, Danni Zheng, Xue Wang, Weihong Zhou, Shuzhen Men, Xinqi Liu
The endocytic and autophagic pathways play important roles in abiotic stress responses and maintaining cellular homeostasis in plants. Asparagine Rich Proteins (NRPs) are plant-specific stress-responsive proteins that are involved in many abiotic stress-related signaling pathways. We previously demonstrated that NRP promotes PIN FORMED 2 (PIN2) vacuolar degradation to maintain PIN2 homeostasis under abscisic acid (ABA) treatment in Arabidopsis (Arabidopsis thaliana). However, the molecular function and mechanism of NRP in cellular vesicle trafficking remain unknown. In this study, we report that NRP directly interacts with LIP5 and ATG8, critical components of the endocytic and autophagic pathways, respectively. Genetic analyses show that NRP overexpression rescues canonical autophagy defects in a LIP5-dependent manner. Cellular and biochemical evidence indicates that NRP-LIP5 recruits ATG8 to multivesicular bodies for further vacuolar degradation, implying that a novel NRP-mediated endocytic pathway is utilized to compensate for the canonical autophagy defects that occur during plant stress responses. These findings provide insights into the crosstalk between the endocytic and autophagic pathways and uncover a function of ATG8 distinct from its canonical role in autophagy. The mechanism revealed here confers an evolutionary advantage to plants and provides a molecular basis for breeding crops with greater stress tolerance.
{"title":"The ASPARAGINE-RICH PROTEIN–LYST-INTERACTING PROTEIN5 complex regulates non-canonical AUTOPHAGY8 degradation in Arabidopsis","authors":"Yanying Wu, Kaikai Zhu, Si Chen, Enzhen Xing, Jiajia Li, Wenqi Tian, Ming Gao, Jiaxin Kong, Danni Zheng, Xue Wang, Weihong Zhou, Shuzhen Men, Xinqi Liu","doi":"10.1093/plphys/kiaf037","DOIUrl":"https://doi.org/10.1093/plphys/kiaf037","url":null,"abstract":"The endocytic and autophagic pathways play important roles in abiotic stress responses and maintaining cellular homeostasis in plants. Asparagine Rich Proteins (NRPs) are plant-specific stress-responsive proteins that are involved in many abiotic stress-related signaling pathways. We previously demonstrated that NRP promotes PIN FORMED 2 (PIN2) vacuolar degradation to maintain PIN2 homeostasis under abscisic acid (ABA) treatment in Arabidopsis (Arabidopsis thaliana). However, the molecular function and mechanism of NRP in cellular vesicle trafficking remain unknown. In this study, we report that NRP directly interacts with LIP5 and ATG8, critical components of the endocytic and autophagic pathways, respectively. Genetic analyses show that NRP overexpression rescues canonical autophagy defects in a LIP5-dependent manner. Cellular and biochemical evidence indicates that NRP-LIP5 recruits ATG8 to multivesicular bodies for further vacuolar degradation, implying that a novel NRP-mediated endocytic pathway is utilized to compensate for the canonical autophagy defects that occur during plant stress responses. These findings provide insights into the crosstalk between the endocytic and autophagic pathways and uncover a function of ATG8 distinct from its canonical role in autophagy. The mechanism revealed here confers an evolutionary advantage to plants and provides a molecular basis for breeding crops with greater stress tolerance.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"49 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143031404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cold stress severely impacts the quality and yield of grapevine (Vitis L.). In this study, we extend our previous work to elucidate the role and regulatory mechanisms of Vitis amurensis MYB transcription factor 4a (VaMYB4a) in grapevine's response to cold stress. Our results identified VaMYB4a as a key positive regulator of cold stress. We demonstrated that VaMYB4a undergoes phosphorylation by V. amurensis CBL-interacting protein kinase 18 (VaCIPK18) under cold stress, a process that activates VaMYB4a transcriptional activity. Using ChIP-seq, we performed a comprehensive genomic search to identify downstream components that interact with VaMYB4a, leading to the discovery of a basic helix-loop-helix (bHLH) transcription factor, V. amurensis phytochrome-interacting factor 3 (VaPIF3). VaMYB4a attenuated the transcriptional activity of VaPIF3 through a phosphorylation-dependent interaction under cold conditions. Furthermore, VaPIF3, which interacts with and inhibits V. amurensis C-repeat binding factor 4 (VaCBF4, a known positive regulator of cold stress), has its activity attenuated by VaMYB4a, which mediates the modulation of this pathway. Notably, VaMYB4a also interacted with and promoted the expression of VaCBF4 in a phosphorylation-dependent manner. Our study shows that VaMYB4a positively modulates cold tolerance in plants by simultaneously downregulating VaPIF3 and upregulating VaCBF4. These findings provide a nuanced understanding of the transcriptional response in grapevine under cold stress and contribute to the broader field of plant stress physiology.
{"title":"Phosphorylation-dependent VaMYB4a regulates cold stress in grapevine by inhibiting VaPIF3 and activating VaCBF4","authors":"Qinhan Yu, Qiaoling Zheng, Chang Liu, Junxia Zhang, Yaping Xie, Wenkong Yao, Jiaxin Li, Ningbo Zhang, Xinyi Hao, Weirong Xu","doi":"10.1093/plphys/kiaf035","DOIUrl":"https://doi.org/10.1093/plphys/kiaf035","url":null,"abstract":"Cold stress severely impacts the quality and yield of grapevine (Vitis L.). In this study, we extend our previous work to elucidate the role and regulatory mechanisms of Vitis amurensis MYB transcription factor 4a (VaMYB4a) in grapevine's response to cold stress. Our results identified VaMYB4a as a key positive regulator of cold stress. We demonstrated that VaMYB4a undergoes phosphorylation by V. amurensis CBL-interacting protein kinase 18 (VaCIPK18) under cold stress, a process that activates VaMYB4a transcriptional activity. Using ChIP-seq, we performed a comprehensive genomic search to identify downstream components that interact with VaMYB4a, leading to the discovery of a basic helix-loop-helix (bHLH) transcription factor, V. amurensis phytochrome-interacting factor 3 (VaPIF3). VaMYB4a attenuated the transcriptional activity of VaPIF3 through a phosphorylation-dependent interaction under cold conditions. Furthermore, VaPIF3, which interacts with and inhibits V. amurensis C-repeat binding factor 4 (VaCBF4, a known positive regulator of cold stress), has its activity attenuated by VaMYB4a, which mediates the modulation of this pathway. Notably, VaMYB4a also interacted with and promoted the expression of VaCBF4 in a phosphorylation-dependent manner. Our study shows that VaMYB4a positively modulates cold tolerance in plants by simultaneously downregulating VaPIF3 and upregulating VaCBF4. These findings provide a nuanced understanding of the transcriptional response in grapevine under cold stress and contribute to the broader field of plant stress physiology.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"34 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143030733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Photoperiodic regulation of flowering time plays a critical role in plant reproductive success and crop yield. In Arabidopsis thaliana, the expression of the CONSTANS (CO) gene is closely regulated by day length and is modulated by both environmental and endogenous cues for precise control over flowering. Our findings reveal that the phytohormone brassinosteroid (BR) pathway represses flowering by inhibiting the expression of both CO and Flowering Locus T (FT). Additionally, we discovered that BRASSINAZOLE RESISTANT 1 (BZR1), a key transcription factor in the BR signaling pathway, directly binds to the proximal promoter region of CO to suppress its transcription during long days, thus regulating photoperiodic flowering. Genetically, BZR1 acts upstream of CO and FT to delay floral initiation depending on day length. Overall, our study reveals how a molecular module comprising BZR1-CO integrates signals from BR as well as photoperiodicity for appropriate adjustment of flowering time.
{"title":"BRASSINAZOLE RESISTANT 1 delays photoperiodic flowering by repressing CONSTANS transcription","authors":"Xingwen Xu, Wenbo Jiang, Yangbo Chen, Hao Tian, Zijian Yang, Shuo Liu, Xiaopeng Li, Chunhui Song, Zhangli Ye, Wei Guo, Dongdong Kong, Congcong Hou, Legong Li, Liangyu Liu","doi":"10.1093/plphys/kiaf032","DOIUrl":"https://doi.org/10.1093/plphys/kiaf032","url":null,"abstract":"Photoperiodic regulation of flowering time plays a critical role in plant reproductive success and crop yield. In Arabidopsis thaliana, the expression of the CONSTANS (CO) gene is closely regulated by day length and is modulated by both environmental and endogenous cues for precise control over flowering. Our findings reveal that the phytohormone brassinosteroid (BR) pathway represses flowering by inhibiting the expression of both CO and Flowering Locus T (FT). Additionally, we discovered that BRASSINAZOLE RESISTANT 1 (BZR1), a key transcription factor in the BR signaling pathway, directly binds to the proximal promoter region of CO to suppress its transcription during long days, thus regulating photoperiodic flowering. Genetically, BZR1 acts upstream of CO and FT to delay floral initiation depending on day length. Overall, our study reveals how a molecular module comprising BZR1-CO integrates signals from BR as well as photoperiodicity for appropriate adjustment of flowering time.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"10 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qiang Zhang, Derong Gao, Lei Tian, Kirstin Feussner, Bin Li, Long Yang, Qin Yang, Yuelin Zhang, Xin Li, Ivo Feussner, Fang Xu
Proteins with Toll/interleukin-1 receptor (TIR) domains are widely distributed in both prokaryotes and eukaryotes, serving as essential components of immune signaling. Although monocots lack the major TIR-nucleotide-binding (NB)-leucine-rich repeat (LRR)-type (TNL) immune receptors, they possess a small number of TIR-only proteins, the function of which remains largely unknown. In the monocot maize (Zea mays), there are three conserved TIR-only genes in the reference genome, namely ZmTIR1 to ZmTIR3. A genome-wide scan for TIR genes and comparative analysis revealed that these genes exhibit low sequence diversity and do not show copy number variation among 26 diverse inbred lines. ZmTIR1 and ZmTIR3, but not ZmTIR2, specifically trigger cell death and defense gene expression when overexpressed in Nicotiana benthamiana leaves. These responses depend on the critical glutamic acid and cysteine residues predicted to be essential for TIR-mediated NADase and 2’,3’-cAMP/cGMP synthetase activity, respectively, as well as the key TIR downstream regulator Enhanced Disease Susceptibility 1 (EDS1). Overexpression of ZmTIR3 in N. benthamiana produces signaling molecules, including 2’cADPR, 2’,3’-cAMP and 2’,3’-cGMP, a process that requires the enzymatic glutamic acid and cysteine residues of ZmTIR3. ZmTIR expression in maize is barely detectable under normal conditions, but is substantially induced by different pathogens. Importantly, the maize Zmtir3 knockout mutant exhibits enhanced susceptibility to the fungal pathogen Cochliobolus heterostrophus, highlighting the role of ZmTIR3 in maize immunity. Overall, our results unveil the function of the maize ZmTIRs. We propose that the pathogen-inducible ZmTIRs play an important role in maize immunity, likely through their enzymatic activity and via EDS1-mediated signaling.
{"title":"Toll/interleukin-1 receptor-only genes contribute to immune responses in maize","authors":"Qiang Zhang, Derong Gao, Lei Tian, Kirstin Feussner, Bin Li, Long Yang, Qin Yang, Yuelin Zhang, Xin Li, Ivo Feussner, Fang Xu","doi":"10.1093/plphys/kiaf030","DOIUrl":"https://doi.org/10.1093/plphys/kiaf030","url":null,"abstract":"Proteins with Toll/interleukin-1 receptor (TIR) domains are widely distributed in both prokaryotes and eukaryotes, serving as essential components of immune signaling. Although monocots lack the major TIR-nucleotide-binding (NB)-leucine-rich repeat (LRR)-type (TNL) immune receptors, they possess a small number of TIR-only proteins, the function of which remains largely unknown. In the monocot maize (Zea mays), there are three conserved TIR-only genes in the reference genome, namely ZmTIR1 to ZmTIR3. A genome-wide scan for TIR genes and comparative analysis revealed that these genes exhibit low sequence diversity and do not show copy number variation among 26 diverse inbred lines. ZmTIR1 and ZmTIR3, but not ZmTIR2, specifically trigger cell death and defense gene expression when overexpressed in Nicotiana benthamiana leaves. These responses depend on the critical glutamic acid and cysteine residues predicted to be essential for TIR-mediated NADase and 2’,3’-cAMP/cGMP synthetase activity, respectively, as well as the key TIR downstream regulator Enhanced Disease Susceptibility 1 (EDS1). Overexpression of ZmTIR3 in N. benthamiana produces signaling molecules, including 2’cADPR, 2’,3’-cAMP and 2’,3’-cGMP, a process that requires the enzymatic glutamic acid and cysteine residues of ZmTIR3. ZmTIR expression in maize is barely detectable under normal conditions, but is substantially induced by different pathogens. Importantly, the maize Zmtir3 knockout mutant exhibits enhanced susceptibility to the fungal pathogen Cochliobolus heterostrophus, highlighting the role of ZmTIR3 in maize immunity. Overall, our results unveil the function of the maize ZmTIRs. We propose that the pathogen-inducible ZmTIRs play an important role in maize immunity, likely through their enzymatic activity and via EDS1-mediated signaling.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"32 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yong-Kang Li, Yu-Meng Zhang, Guang-Yi Dai, Yi-Li Chen, Ding-Kang Chen, Nan Yao
Osmotic stress caused by drought, salinity, or cold conditions is an important abiotic factor that decreases membrane integrity and causes cell death, thus decreasing plant growth and productivity. Remodeling cell membrane composition via lipid turnover can counter the loss of membrane integrity and cell death caused by osmotic stress. Sphingolipids are important components of eukaryotic membrane systems; however, how sphingolipids participate in plant responses to osmotic stress remains unclear. Here, we characterized the role of the glucosylceramidase (GCD) AtGCD1 (encoded by At1g33700) in sphingolipid remodeling and acclimation to osmotic stress in Arabidopsis (Arabidopsis thaliana). AtGCD1–AtGCD4 are Arabidopsis homologs of human nonlysosomal glucosylceramidase. We determined that AtGCD1 functions as a glucosylceramidase and localizes to the plasma membrane and that recombinant AtGCD1 has no substrate preference for acyl chain length. Moreover, AtGCD1 and AtGCD3 (At4g10060) are essential for osmotic stress tolerance in Arabidopsis. In cells treated with mannitol, AtGCD1 and AtGCD3 hydrolyzed glucosylceramides to ceramides, leading to decreased glucosylceramide contents and increased glycosyl inositol phosphoceramide contents. We observed a substantial change in the molecular order of lipids and membrane tension at the plasma membrane of the Arabidopsis gcd1 gcd3 double mutant, indicating that glucosylceramidases compensate for changes in membrane properties to stabilize the membrane during osmotic stress. Notably, we found that loss of GCD1 and GCD3 enhanced plant resistance to beet armyworm (Spodoptera exigua). Our results suggest that sphingolipid remodeling regulates the physicochemical properties of cellular membranes during plant stress responses.
{"title":"Sphingolipid remodeling in the plasma membrane is essential for osmotic stress tolerance in Arabidopsis","authors":"Yong-Kang Li, Yu-Meng Zhang, Guang-Yi Dai, Yi-Li Chen, Ding-Kang Chen, Nan Yao","doi":"10.1093/plphys/kiaf031","DOIUrl":"https://doi.org/10.1093/plphys/kiaf031","url":null,"abstract":"Osmotic stress caused by drought, salinity, or cold conditions is an important abiotic factor that decreases membrane integrity and causes cell death, thus decreasing plant growth and productivity. Remodeling cell membrane composition via lipid turnover can counter the loss of membrane integrity and cell death caused by osmotic stress. Sphingolipids are important components of eukaryotic membrane systems; however, how sphingolipids participate in plant responses to osmotic stress remains unclear. Here, we characterized the role of the glucosylceramidase (GCD) AtGCD1 (encoded by At1g33700) in sphingolipid remodeling and acclimation to osmotic stress in Arabidopsis (Arabidopsis thaliana). AtGCD1–AtGCD4 are Arabidopsis homologs of human nonlysosomal glucosylceramidase. We determined that AtGCD1 functions as a glucosylceramidase and localizes to the plasma membrane and that recombinant AtGCD1 has no substrate preference for acyl chain length. Moreover, AtGCD1 and AtGCD3 (At4g10060) are essential for osmotic stress tolerance in Arabidopsis. In cells treated with mannitol, AtGCD1 and AtGCD3 hydrolyzed glucosylceramides to ceramides, leading to decreased glucosylceramide contents and increased glycosyl inositol phosphoceramide contents. We observed a substantial change in the molecular order of lipids and membrane tension at the plasma membrane of the Arabidopsis gcd1 gcd3 double mutant, indicating that glucosylceramidases compensate for changes in membrane properties to stabilize the membrane during osmotic stress. Notably, we found that loss of GCD1 and GCD3 enhanced plant resistance to beet armyworm (Spodoptera exigua). Our results suggest that sphingolipid remodeling regulates the physicochemical properties of cellular membranes during plant stress responses.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"1 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE (RUBISCO) is the most abundant enzyme and CO2 bio-sequestration system on Earth. Its in vivo activity is usually determined by 14CO2 incorporation into 3-phosphoglycerate (3PGA). However, the radiometric analysis of 3PGA does not distinguish carbon positions. Hence, RUBISCO activity that fixes carbon into the 1-C position of 3PGA and Calvin-Benson-Bassham (CBB) cycle activities that redistribute carbon into its 2-C and 3-C positions are not resolved. This study aims to develop technology that differentiates between these activities. In source fragmentation of gas chromatography-mass spectrometry (GC-MS) enables paired isotopologue distribution analyses of fragmented substructures and the complete metabolite structure. GC-MS measurements after dynamic photosynthetic 13CO2 labelling allowed quantification of the 13C fractional enrichment (E13C) and molar carbon assimilation rates (A13C) at carbon position 1-C of 3PGA by combining E13C from carbon positions 2,3-C2 and 1,2,3-C3 with quantification of 3PGA concentrations. We validated the procedure using two GC-time of flight (TOF)-MS instruments, operated at nominal or high mass resolution, and tested the expected 3PGA positional labelling by in vivo glycolysis of positional labelled glucose isotopomers. Mutant analysis of the highly divergent GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASEs (GAPDH1 and 2) from Synechocystis sp. PCC 6803 revealed full inactivation of the CBB cycle with maintained RUBISCO activity in Δgapdh2 and a CBB cycle modulating role of GAPDH1 under fluctuating CO2 supply. RUBISCO activity in the CBB-deficient Δgapdh2 can re-assimilate CO2 released by catabolic pathways. We suggest that RUBISCO activity in Synechocystis can scavenge carbon lost through the pentose phosphate pathway or other cellular decarboxylation reactions.
{"title":"Dynamic photosynthetic labeling and carbon-positional mass spectrometry monitor in vivo Rubisco carbon assimilation rates.","authors":"Yogeswari Rajarathinam,Luisa Wittemeier,Kirstin Gutekunst,Martin Hagemann,Joachim Kopka","doi":"10.1093/plphys/kiaf020","DOIUrl":"https://doi.org/10.1093/plphys/kiaf020","url":null,"abstract":"RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE (RUBISCO) is the most abundant enzyme and CO2 bio-sequestration system on Earth. Its in vivo activity is usually determined by 14CO2 incorporation into 3-phosphoglycerate (3PGA). However, the radiometric analysis of 3PGA does not distinguish carbon positions. Hence, RUBISCO activity that fixes carbon into the 1-C position of 3PGA and Calvin-Benson-Bassham (CBB) cycle activities that redistribute carbon into its 2-C and 3-C positions are not resolved. This study aims to develop technology that differentiates between these activities. In source fragmentation of gas chromatography-mass spectrometry (GC-MS) enables paired isotopologue distribution analyses of fragmented substructures and the complete metabolite structure. GC-MS measurements after dynamic photosynthetic 13CO2 labelling allowed quantification of the 13C fractional enrichment (E13C) and molar carbon assimilation rates (A13C) at carbon position 1-C of 3PGA by combining E13C from carbon positions 2,3-C2 and 1,2,3-C3 with quantification of 3PGA concentrations. We validated the procedure using two GC-time of flight (TOF)-MS instruments, operated at nominal or high mass resolution, and tested the expected 3PGA positional labelling by in vivo glycolysis of positional labelled glucose isotopomers. Mutant analysis of the highly divergent GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASEs (GAPDH1 and 2) from Synechocystis sp. PCC 6803 revealed full inactivation of the CBB cycle with maintained RUBISCO activity in Δgapdh2 and a CBB cycle modulating role of GAPDH1 under fluctuating CO2 supply. RUBISCO activity in the CBB-deficient Δgapdh2 can re-assimilate CO2 released by catabolic pathways. We suggest that RUBISCO activity in Synechocystis can scavenge carbon lost through the pentose phosphate pathway or other cellular decarboxylation reactions.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"6 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142991831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In plants, cytoskeletal proteins assemble into dynamic polymers that play numerous roles in diverse fundamental cellular processes, including endocytosis, vesicle trafficking, and the spatial distribution of organelles and protein complexes. Plant elicitor peptides (Peps) are damage/danger-associated molecular patterns (DAMPs) that are perceived by the receptor-like kinases PEP RECEPTOR 1 (PEPR1) and PEPR2 to enhance innate immunity and inhibit root growth in Arabidopsis (Arabidopsis thaliana). To date, however, there is little evidence that the actin cytoskeleton of the host cell participates in DAMP-induced innate immunity. Here, we demonstrated that the actin cytoskeleton alters the Pep1-triggered immune response. In addition, dual-color total internal reflection fluorescence–structured illumination microscopy (TIRF-SIM) showed that PEPR1 diffusion on the plasma membrane is closely related to the actin cytoskeleton. We performed single-particle tracking to quantify individual protein particles and found that the actin cytoskeleton notably regulates PEPR1 mobility and cluster size. More importantly, we demonstrated that actin filament reconfiguration is sufficient to inhibit Pep1-induced internalization, which alters the immune response. Taken together, these findings suggest that the actin cytoskeleton functions as an integration node for Pep1 signaling and PEPR1 endocytosis.
{"title":"The actin cytoskeleton regulates danger-associated molecular pattern signaling and PEP1 RECEPTOR1 internalization","authors":"Hongping Qian, Xinxiu Zuo, Yi Man, Changwen Xu, Pengyun Luo, Lijuan Yao, Ruohan Geng, Binghe Wang, Shihui Niu, Jinxing Lin, Yaning Cui","doi":"10.1093/plphys/kiaf023","DOIUrl":"https://doi.org/10.1093/plphys/kiaf023","url":null,"abstract":"In plants, cytoskeletal proteins assemble into dynamic polymers that play numerous roles in diverse fundamental cellular processes, including endocytosis, vesicle trafficking, and the spatial distribution of organelles and protein complexes. Plant elicitor peptides (Peps) are damage/danger-associated molecular patterns (DAMPs) that are perceived by the receptor-like kinases PEP RECEPTOR 1 (PEPR1) and PEPR2 to enhance innate immunity and inhibit root growth in Arabidopsis (Arabidopsis thaliana). To date, however, there is little evidence that the actin cytoskeleton of the host cell participates in DAMP-induced innate immunity. Here, we demonstrated that the actin cytoskeleton alters the Pep1-triggered immune response. In addition, dual-color total internal reflection fluorescence–structured illumination microscopy (TIRF-SIM) showed that PEPR1 diffusion on the plasma membrane is closely related to the actin cytoskeleton. We performed single-particle tracking to quantify individual protein particles and found that the actin cytoskeleton notably regulates PEPR1 mobility and cluster size. More importantly, we demonstrated that actin filament reconfiguration is sufficient to inhibit Pep1-induced internalization, which alters the immune response. Taken together, these findings suggest that the actin cytoskeleton functions as an integration node for Pep1 signaling and PEPR1 endocytosis.","PeriodicalId":20101,"journal":{"name":"Plant Physiology","volume":"70 1","pages":""},"PeriodicalIF":7.4,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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