In tomato, the NBARC-LRR resistance （R） protein Prf acts in concert with the Pto or Fen kinase to determine immunity against Pseudomonas syringae pv. tomato （Pst）. Prf-mediated defense signaling is initiated by th...In tomato, the NBARC-LRR resistance （R） protein Prf acts in concert with the Pto or Fen kinase to determine immunity against Pseudomonas syringae pv. tomato （Pst）. Prf-mediated defense signaling is initiated by the recognition of two sequence-unrelated Pst-secreted effector proteins, AvrPto and AvrPtoB, by tomato Pto or Fen. Prf detects these inter- actions and activates signaling leading to host defense responses including localized programmed cell death （PCD） that is associated with the arrest of Pst growth. We found that Prf variants with single amino acid substitutions at D1416 in the IHD motif （isoleucine-histidine-aspartic acid） in the NBARC domain cause effector-independent PCD when transiently expressed in leaves of Nicotiana benthamiana, suggesting D1416 plays an important role in activation of Prf. The N-ter- minal region of Prf （NPrf） and the LRR domain are required for this autoactive Prf cell death signaling but dispensable for accumulation of the PrfD1416V protein. Significantly, co-expression of the Prf LRR but not NPrf, with PrfD1416v, AvrPto/Pto, AvrPtoB/Pto, an autoactive form of Pro （PtoY207D）, or Fen completely suppresses PCD. However, the Prf LRR does not in- terfere with PCD caused by Rpi-blblD475v a distinct R protein-mediated PCD signaling event, or that caused by overex- pression of MAPKKKα, a protein acting downstream of Prf. Furthermore, we found the PrfD1416V protein is unable to accumulate in plant cells when co-expressed with the Prf LRR domain, likely explaining the cell death suppression. The mechanism for the LRR-induced degradation of PrfD1416V is unknown but may involve interference in the intramo- lecular interactions of Prf or to binding of the unattached LRR to other host proteins that are needed for Prf stability.展开更多
Plasma membrane-localized receptor-like kinases(RLKs)perceive conserved pathogen-associated molecular pattems(PAMPs)in plants,leading to PAMP-triggered immunity(PTI).TheArabidopsis thaliana lectin RLK LecRK-Ⅸ.2 has b...Plasma membrane-localized receptor-like kinases(RLKs)perceive conserved pathogen-associated molecular pattems(PAMPs)in plants,leading to PAMP-triggered immunity(PTI).TheArabidopsis thaliana lectin RLK LecRK-Ⅸ.2 has been shown to regulate the bacterial flagellin-derived peptide flg22-induced PTI.Here,we discover that Pseudomonas syringae effector AvrPtoB targets LecRK-Ⅸ.2 for degradation,which subsequently suppresses LecRK-Ⅸ.2-mediated PTI and disease resistance.However,LecRK-Ⅸ.2 can interact with and phosphorylate AvrPtoB at serine site 335(S335).AvrPtoB self-associates in vitro and in vivo,and the association appears to be essential for its E3 ligase activity in ubiquitinating substrate in plants.Phosphorylation of S335 disrupts the self-association and as a result,phosphomimetic AvrPtoBS335D cannot ubiquitinate LecRK-Ⅸ.2 efficiently,leading to the compromised virulence of AvrPtoB in suppressing PTI responses.fig22 enhances AvrPtoB S335 phosphorylation by inducing the expression and activating of LecRK-Ⅸ.2.Our study demonstrates that host RLKs can modify pathogen effectors to dampen their virulence and undermine their ability in suppressing PTI.展开更多
A critical component controlling bacterial virulence is the delivery of pathogen effectors into plant cells during infection.Effectors alter host metabolism and immunity for the benefit of pathogens.Multiple effectors...A critical component controlling bacterial virulence is the delivery of pathogen effectors into plant cells during infection.Effectors alter host metabolism and immunity for the benefit of pathogens.Multiple effectors are phosphorylated by host kinases,and this posttranslational modification is important for their activity.We sought to identify host kinases involved in effector phosphorylation.Multiple phosphorylated effector residues matched the proposed consensus motif for the plant calcium-dependent protein kinase(CDPK)and Snf1-related kinase(SnRK)superfamily.The conserved Pseudomonas effector AvrPtoB acts as an E3 ubiquitin ligase and promotes bacterial virulence.In this study,we identified a member of the Arabidopsis SnRK family,SnRK2.8,which interacts with AvrPtoB in yeast and in planta.We showed that SnRK2.8 was required for AvrPtoB virulence functions,including facilitating bacterial colonization,suppression of callose deposition,and targeting the plant defense regulator NPR1 and analyses receptor FLS2.Mass spectrometry analysis revealed that AvrPtoB phosphorylation occurs at multiple serine residues in planta,with S258 phosphorylation significantly reduced in the snrk2.8 knockout.AvrPtoB phospho-'null'mutants exhibited compromised virulence functions and were unable to suppress NPR1 accumulation,FLS2 accumulation,or inhibit FLS2-BAK1 complex formation upon flagellin perception.Taken together,these data identify a conserved plant kinase utilized by a pathogen effector to promote disease.展开更多
基金the University of Idaho Startup funding to F.X.,the Knowledge Innovation Program of Chinese Academy of Sciences (KSCX2-EW-J-22) to X.M.,the National Science Fund for Distinguished Young Scholars (No.30825030) to Y.L.,and the National Science Foundation grant (DBI-0605059) to G.B.M
文摘In tomato, the NBARC-LRR resistance （R） protein Prf acts in concert with the Pto or Fen kinase to determine immunity against Pseudomonas syringae pv. tomato （Pst）. Prf-mediated defense signaling is initiated by the recognition of two sequence-unrelated Pst-secreted effector proteins, AvrPto and AvrPtoB, by tomato Pto or Fen. Prf detects these inter- actions and activates signaling leading to host defense responses including localized programmed cell death （PCD） that is associated with the arrest of Pst growth. We found that Prf variants with single amino acid substitutions at D1416 in the IHD motif （isoleucine-histidine-aspartic acid） in the NBARC domain cause effector-independent PCD when transiently expressed in leaves of Nicotiana benthamiana, suggesting D1416 plays an important role in activation of Prf. The N-ter- minal region of Prf （NPrf） and the LRR domain are required for this autoactive Prf cell death signaling but dispensable for accumulation of the PrfD1416V protein. Significantly, co-expression of the Prf LRR but not NPrf, with PrfD1416v, AvrPto/Pto, AvrPtoB/Pto, an autoactive form of Pro （PtoY207D）, or Fen completely suppresses PCD. However, the Prf LRR does not in- terfere with PCD caused by Rpi-blblD475v a distinct R protein-mediated PCD signaling event, or that caused by overex- pression of MAPKKKα, a protein acting downstream of Prf. Furthermore, we found the PrfD1416V protein is unable to accumulate in plant cells when co-expressed with the Prf LRR domain, likely explaining the cell death suppression. The mechanism for the LRR-induced degradation of PrfD1416V is unknown but may involve interference in the intramo- lecular interactions of Prf or to binding of the unattached LRR to other host proteins that are needed for Prf stability.
基金Chinese Academy of Sciences(Strategic Pri-ority Research Program grant no.XDB11020300)the National Key R&D Program of China(2017YFD0200900)+1 种基金the Natural Science Foundation of China(31972257)the State Key Laboratory of Plant Genomics(Grant No.O8KF021011)to J.L.
文摘Plasma membrane-localized receptor-like kinases(RLKs)perceive conserved pathogen-associated molecular pattems(PAMPs)in plants,leading to PAMP-triggered immunity(PTI).TheArabidopsis thaliana lectin RLK LecRK-Ⅸ.2 has been shown to regulate the bacterial flagellin-derived peptide flg22-induced PTI.Here,we discover that Pseudomonas syringae effector AvrPtoB targets LecRK-Ⅸ.2 for degradation,which subsequently suppresses LecRK-Ⅸ.2-mediated PTI and disease resistance.However,LecRK-Ⅸ.2 can interact with and phosphorylate AvrPtoB at serine site 335(S335).AvrPtoB self-associates in vitro and in vivo,and the association appears to be essential for its E3 ligase activity in ubiquitinating substrate in plants.Phosphorylation of S335 disrupts the self-association and as a result,phosphomimetic AvrPtoBS335D cannot ubiquitinate LecRK-Ⅸ.2 efficiently,leading to the compromised virulence of AvrPtoB in suppressing PTI responses.fig22 enhances AvrPtoB S335 phosphorylation by inducing the expression and activating of LecRK-Ⅸ.2.Our study demonstrates that host RLKs can modify pathogen effectors to dampen their virulence and undermine their ability in suppressing PTI.
基金the United States Department of Agriculture:USDA-NIFA 2015-67013-23082,and NIH R01GM092772 and R35GM136402,awarded to G.C.
文摘A critical component controlling bacterial virulence is the delivery of pathogen effectors into plant cells during infection.Effectors alter host metabolism and immunity for the benefit of pathogens.Multiple effectors are phosphorylated by host kinases,and this posttranslational modification is important for their activity.We sought to identify host kinases involved in effector phosphorylation.Multiple phosphorylated effector residues matched the proposed consensus motif for the plant calcium-dependent protein kinase(CDPK)and Snf1-related kinase(SnRK)superfamily.The conserved Pseudomonas effector AvrPtoB acts as an E3 ubiquitin ligase and promotes bacterial virulence.In this study,we identified a member of the Arabidopsis SnRK family,SnRK2.8,which interacts with AvrPtoB in yeast and in planta.We showed that SnRK2.8 was required for AvrPtoB virulence functions,including facilitating bacterial colonization,suppression of callose deposition,and targeting the plant defense regulator NPR1 and analyses receptor FLS2.Mass spectrometry analysis revealed that AvrPtoB phosphorylation occurs at multiple serine residues in planta,with S258 phosphorylation significantly reduced in the snrk2.8 knockout.AvrPtoB phospho-'null'mutants exhibited compromised virulence functions and were unable to suppress NPR1 accumulation,FLS2 accumulation,or inhibit FLS2-BAK1 complex formation upon flagellin perception.Taken together,these data identify a conserved plant kinase utilized by a pathogen effector to promote disease.
