Bacterial flagellins are often recognized by the receptor kinase FLAGELLIN SENSITIVE2 （FLS2） and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize...Bacterial flagellins are often recognized by the receptor kinase FLAGELLIN SENSITIVE2 （FLS2） and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize flagellins of key rice pathogens and its biological relevance remain poorly understood. We demonstrate that ectopically expressed OsFLS2 in Arabidopsis senses the eliciting fig22 peptide and in vitro purified Acidovorax avenae （Aa） flagellin in an expression level-dependent manner, but does not recognize purified flagellins or derivative fig22x~ peptides ofXanthomonas oryzae pvs. oryzae （Xoo） and or- yzicola （Xoc）. Consistently, the fig22 peptide and purified Aa flageUin, but not Xoo/Xoc flagellins, induce various immune responses such as defense gene induction and MAPK activation in rice. Perception of flagellin by rice does induce strong resistance to Xoo infection, as shown after pre-treatment of rice leaves with Aa flagellin. OsFLS2 was found to differ from AtFLS2 in its perception specificities or sensitivities to different fig22 sequences. In addition, post-translational modification of Xoc flagellin was altered by dele- tion of glycosyltransferase-encoding rbfC, but this had little effect on Xoc motility and rpfC mutation did not detectably reduce Xoc virulence on rice. Deletion of flagellin-encoding fliC from Xoo/Xoc blocked swim- ming motility but also did not significantly alter Xoo/Xoc virulence. These results suggest that Xoo/Xoc carry flg22-region amino acid changes that allow motility while evading the ancient flagellin detection sys- tem in rice, which retains recognition capacity for other bacterial pathogens.展开更多
文摘Bacterial flagellins are often recognized by the receptor kinase FLAGELLIN SENSITIVE2 （FLS2） and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize flagellins of key rice pathogens and its biological relevance remain poorly understood. We demonstrate that ectopically expressed OsFLS2 in Arabidopsis senses the eliciting fig22 peptide and in vitro purified Acidovorax avenae （Aa） flagellin in an expression level-dependent manner, but does not recognize purified flagellins or derivative fig22x~ peptides ofXanthomonas oryzae pvs. oryzae （Xoo） and or- yzicola （Xoc）. Consistently, the fig22 peptide and purified Aa flageUin, but not Xoo/Xoc flagellins, induce various immune responses such as defense gene induction and MAPK activation in rice. Perception of flagellin by rice does induce strong resistance to Xoo infection, as shown after pre-treatment of rice leaves with Aa flagellin. OsFLS2 was found to differ from AtFLS2 in its perception specificities or sensitivities to different fig22 sequences. In addition, post-translational modification of Xoc flagellin was altered by dele- tion of glycosyltransferase-encoding rbfC, but this had little effect on Xoc motility and rpfC mutation did not detectably reduce Xoc virulence on rice. Deletion of flagellin-encoding fliC from Xoo/Xoc blocked swim- ming motility but also did not significantly alter Xoo/Xoc virulence. These results suggest that Xoo/Xoc carry flg22-region amino acid changes that allow motility while evading the ancient flagellin detection sys- tem in rice, which retains recognition capacity for other bacterial pathogens.
