Cyclic nucleotide-gatedion channels(CNGCs)are key components in pattern-triggeredimmunity(PTl)signaling.Tight control of CNGC homeostasis is crucial for maintaining a balance between plant growth and immunity.Neverthe...Cyclic nucleotide-gatedion channels(CNGCs)are key components in pattern-triggeredimmunity(PTl)signaling.Tight control of CNGC homeostasis is crucial for maintaining a balance between plant growth and immunity.Nevertheless,the mechanisms for fine-tuning CNGC homeostasis remain largely unknown.Here,we report that Arabidopsis thaliana CNGC3 is a functionalcalcium channel to mediate patterninduced Ca2+influx,PTl,and resistance to Sclerotinia sclerotiorum.We identified a CNGC interactor,Skp1-interacting protein 31(SKIP31).In the absence of a pathogen,SKIP31ubiquitinates CNGC3 at Lys8 and Lys33 of the K-X-V-R motif for degradation to repress plant immunity.When a pathogen attacks,activated receptor-like cytoplasmic kinase(RLCK)BOTRYTIS-INDUCED KINASE1(BIK1)phosphorylates SKIP31 to inhibit its ubiquitin ligase activity and interaction with the CNGC3 N-terminal region,thereby suppressing CNGC3 protein degradation to promote immunity.Phosphorylation within the F box of SKlP31 at Ser88 and Ser93 and at the C-terminal Ser261 prevents its interaction with Skp1 and CNGC3,respectively.These phosphorylation sites are conserved in SKlP31 of different plant species,and SKlP31 interacts with all examined CNGCs,suggesting a pivotal role of SKIP31 phosphorylation in regulating CNGC stability and plant immunity.Moreover,biochemical assays revealed that BIK1 directly phosphorylates the CNGC3 cytoplasmic C-terminal region at four Ser residues to enhance its Ca²+channel activity,demonstrating dual roles of BlK1 in both promoting CNGC channel activity and stabilizing the channel protein.Collectively,our work unveils an SCF ubiquitin ligase-RLCK control system that fine-tunes the homeostasis of CNGCs for orchestrating plant immunity.展开更多
Summary In Arabidopsis, both the membrane-anchored receptor-like kinase （RLK） BAK1 and the receptor-like cytoplasmic kinase （RLCK） BIK1 are important mediators of transmembrane signal transduction that regulate pl...Summary In Arabidopsis, both the membrane-anchored receptor-like kinase （RLK） BAK1 and the receptor-like cytoplasmic kinase （RLCK） BIK1 are important mediators of transmembrane signal transduction that regulate plant development and immunity. However, little attention has been paid to their genetic association. This study found the bak1 bik1 double mutant of Arabidopsis displayed a severe dwarfism phenotype due to constitutive immunity and cell death in developing plants. These data suggest that BIK1 cooperates with BAK1 to regulate constitutive immunity and cell death.展开更多
Receptor-like kinases(RLKs) play important roles in plant immunity signaling; thus, many are hijacked by pathogen effectors to promote successful pathogenesis. Xanthomonas oryzae pv. oryzae(Xoo) is the causal agent of...Receptor-like kinases(RLKs) play important roles in plant immunity signaling; thus, many are hijacked by pathogen effectors to promote successful pathogenesis. Xanthomonas oryzae pv. oryzae(Xoo) is the causal agent of rice leaf blight disease. The strain PXO99 A has 18 non-TAL(transcription activation-like) effectors; however, their mechanisms of action and host target proteins remain largely unknown. Although the effector XopR from the Xoo strain MAFF311018 was shown to suppress PAMP-triggered immune responses in Arabidopsis, its target has not yet been identified. Here, we show that PXO99 A XopR interacts with BIK1 at the plasma membrane. BIK1 is a receptor-like cytoplasmic kinase(RLCK) belonging to the RLK family of proteins and mediates PAMP-triggered stomatal immunity. In turn, BIK1 phosphorylates XopR. Furthermore, XopR suppresses PAMP-triggered stomatal closure in transgenic Arabidopsis expressing XopR. In addition, XopR is able to associate with RLCKs other than BIK1. These results suggest that XopR likely suppresses plant immunity by targeting BIK1 and other RLCKs.展开更多
Arabidopsis BOTRYTIS-INDUCED KINASE1(BIK1)is a receptor-like cytoplasmic kinase acting early in multiple signaling pathways important for plant growth and innate immunity.It is known to form a signaling complex with a...Arabidopsis BOTRYTIS-INDUCED KINASE1(BIK1)is a receptor-like cytoplasmic kinase acting early in multiple signaling pathways important for plant growth and innate immunity.It is known to form a signaling complex with a cell-surface receptor FLS2 and a co-receptor kinase BAK1 to transduce signals upon perception of pathogen-asso-ciated molecular patterns(PAMPs).Although site-specifi c phosphorylation is speculated to mediate the activation and function of BIK1,few studies have been devoted to complete profiling of BIK1 phosphorylation residues.Here,we identified nineteen in vitro autophosphoryla-tion sites of BIK1 including three phosphotyrosine sites,thereby proving BIK1 is a dual-specifi city kinase for the fi rst time.The kinase activity of BIK1 substitution mutants were explicitly assessed using quantitative mass spec-trometry(MS).Thr-237,Thr-242 and Tyr-250 were found to most signifi cantly affect BIK1 activity in autophosphoryla-tion and phosphorylation of BAK1 in vitro.A structural model of BIK1 was built to further illustrate the molecular functions of specifi c phosphorylation residues.We also mapped new sites of FLS2 phosphorylation by BIK1,which are different from those by BAK1.These in vitro results could provide new hypotheses for more in-depth in vivo studies leading to deeper understanding of how phosphorylation contributes to BIK1 activation and medi-ates downstream signaling specifi city.展开更多
基金National Natural Science Foundation of China(Grant No.60775038)Ningbo Natural Science Foundation of China(Grant No.2009A610078)K.C.Wang Magna Fund in Ningbo University
基金supported by grants from the Zhejiang Province Core Technology Innovation Project in Agriculture,the Hainan Provincial Natural Science Foundation of China(324CXTD430)the National Natural Science Foundation of China(31871947)the Zhejiang Provincial Natural Science Foundation of China(LZ18C140002).
文摘Cyclic nucleotide-gatedion channels(CNGCs)are key components in pattern-triggeredimmunity(PTl)signaling.Tight control of CNGC homeostasis is crucial for maintaining a balance between plant growth and immunity.Nevertheless,the mechanisms for fine-tuning CNGC homeostasis remain largely unknown.Here,we report that Arabidopsis thaliana CNGC3 is a functionalcalcium channel to mediate patterninduced Ca2+influx,PTl,and resistance to Sclerotinia sclerotiorum.We identified a CNGC interactor,Skp1-interacting protein 31(SKIP31).In the absence of a pathogen,SKIP31ubiquitinates CNGC3 at Lys8 and Lys33 of the K-X-V-R motif for degradation to repress plant immunity.When a pathogen attacks,activated receptor-like cytoplasmic kinase(RLCK)BOTRYTIS-INDUCED KINASE1(BIK1)phosphorylates SKIP31 to inhibit its ubiquitin ligase activity and interaction with the CNGC3 N-terminal region,thereby suppressing CNGC3 protein degradation to promote immunity.Phosphorylation within the F box of SKlP31 at Ser88 and Ser93 and at the C-terminal Ser261 prevents its interaction with Skp1 and CNGC3,respectively.These phosphorylation sites are conserved in SKlP31 of different plant species,and SKlP31 interacts with all examined CNGCs,suggesting a pivotal role of SKIP31 phosphorylation in regulating CNGC stability and plant immunity.Moreover,biochemical assays revealed that BIK1 directly phosphorylates the CNGC3 cytoplasmic C-terminal region at four Ser residues to enhance its Ca²+channel activity,demonstrating dual roles of BlK1 in both promoting CNGC channel activity and stabilizing the channel protein.Collectively,our work unveils an SCF ubiquitin ligase-RLCK control system that fine-tunes the homeostasis of CNGCs for orchestrating plant immunity.
基金supported by the National Natural Science Foundation of China(31571249 and 31425003)
文摘Summary In Arabidopsis, both the membrane-anchored receptor-like kinase （RLK） BAK1 and the receptor-like cytoplasmic kinase （RLCK） BIK1 are important mediators of transmembrane signal transduction that regulate plant development and immunity. However, little attention has been paid to their genetic association. This study found the bak1 bik1 double mutant of Arabidopsis displayed a severe dwarfism phenotype due to constitutive immunity and cell death in developing plants. These data suggest that BIK1 cooperates with BAK1 to regulate constitutive immunity and cell death.
基金supported by the National Natural Science Foundation of China(31322009)the National Basic Research Program of China(2015CB910200)the State Key Laboratory of Plant Genomics of China(SKLPG2011B0301,SKLPG2011A0301)
文摘Receptor-like kinases(RLKs) play important roles in plant immunity signaling; thus, many are hijacked by pathogen effectors to promote successful pathogenesis. Xanthomonas oryzae pv. oryzae(Xoo) is the causal agent of rice leaf blight disease. The strain PXO99 A has 18 non-TAL(transcription activation-like) effectors; however, their mechanisms of action and host target proteins remain largely unknown. Although the effector XopR from the Xoo strain MAFF311018 was shown to suppress PAMP-triggered immune responses in Arabidopsis, its target has not yet been identified. Here, we show that PXO99 A XopR interacts with BIK1 at the plasma membrane. BIK1 is a receptor-like cytoplasmic kinase(RLCK) belonging to the RLK family of proteins and mediates PAMP-triggered stomatal immunity. In turn, BIK1 phosphorylates XopR. Furthermore, XopR suppresses PAMP-triggered stomatal closure in transgenic Arabidopsis expressing XopR. In addition, XopR is able to associate with RLCKs other than BIK1. These results suggest that XopR likely suppresses plant immunity by targeting BIK1 and other RLCKs.
基金the National Natural Science Foundation of China(Grant Nos.31170782 and 31100208)Tianjin Natural Science Foundation(Grant No.11JCYBJC25500)Spe-cialized Research Fund for the Doctoral Program of Higher Education(Grant No.20110031120019).
文摘Arabidopsis BOTRYTIS-INDUCED KINASE1(BIK1)is a receptor-like cytoplasmic kinase acting early in multiple signaling pathways important for plant growth and innate immunity.It is known to form a signaling complex with a cell-surface receptor FLS2 and a co-receptor kinase BAK1 to transduce signals upon perception of pathogen-asso-ciated molecular patterns(PAMPs).Although site-specifi c phosphorylation is speculated to mediate the activation and function of BIK1,few studies have been devoted to complete profiling of BIK1 phosphorylation residues.Here,we identified nineteen in vitro autophosphoryla-tion sites of BIK1 including three phosphotyrosine sites,thereby proving BIK1 is a dual-specifi city kinase for the fi rst time.The kinase activity of BIK1 substitution mutants were explicitly assessed using quantitative mass spec-trometry(MS).Thr-237,Thr-242 and Tyr-250 were found to most signifi cantly affect BIK1 activity in autophosphoryla-tion and phosphorylation of BAK1 in vitro.A structural model of BIK1 was built to further illustrate the molecular functions of specifi c phosphorylation residues.We also mapped new sites of FLS2 phosphorylation by BIK1,which are different from those by BAK1.These in vitro results could provide new hypotheses for more in-depth in vivo studies leading to deeper understanding of how phosphorylation contributes to BIK1 activation and medi-ates downstream signaling specifi city.
