AUTHOR=Long Juying , Song Congfeng , Yan Fang , Zhou Junhui , Zhou Huanbin , Yang Bing 

TITLE=Non-TAL Effectors From Xanthomonas oryzae pv. oryzae Suppress Peptidoglycan-Triggered MAPK Activation in Rice

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01857

DOI=10.3389/fpls.2018.01857

ISSN=1664-462X

ABSTRACT=<p><italic>Xanthomonas oryzae</italic> pv. <italic>oryzae</italic>, the causal pathogen of bacterial blight of rice, depends on its type III secretion system and associated effector proteins to grow and colonize the vascular tissues of rice plants. The type III effectors include a family of closely related transcription activator-like (TAL) effectors and the rest of diverse effectors, so-called non-TAL effectors. Our understanding of non-TAL effectors for pathogenesis in rice blight is still limited. Here we report a feasible method to rapidly detect the activation of mitogen-activated protein kinase pathway in rice mesophyll protoplasts by the <italic>X</italic>. <italic>oryzae</italic> pv. <italic>oryzae</italic> derived peptidoglycan and screen for virulent effectors that can suppress the pathogen-associated molecular pattern triggered immunity (PTI) response. Amongst 17 non-TAL effectors transiently expressed in rice cells, we found that three effectors (XopZ, XopN, and XopV) were able to suppress the peptidoglycan-triggered MAPK activation. The triple mutant of the <italic>X. oryzae</italic> pv. <italic>oryzae</italic> strain PXO99<sup>A</sup> lacking <italic>XopZ</italic>, <italic>XopN</italic>, and <italic>XopV</italic> showed additively reduced virulence. Adding back either of genes restored the virulence of the triple mutant. Our results demonstrate the collective and redundant ability of defense suppression by non-TAL effectors in causing bacterial blight of rice.</p>