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.
