Abstract
Many gram-negative bacteria that infect plants directly inject lots of effector proteins into host cells by using a protein secretion system, a so-called type III secretion (TTSS) system. The TTSS effector proteins are considered to be the primary virulence factors and strongly contribute to cause disease on the host plants. Therefore, it is likely that these effectors block the important steps in plant immune response. XopP is one of effector proteins secreted into rice cells through the TTSS of Xanthomonas oryzae pv. oryzae (Xoo : Furutani et al ., MPMI 22(1): 96-106 2009). To understand the inhibitory mechanism of host immune response by XopP, we have generated transgenic rice plants expressing XopP . The transgenic plants showed an enhanced susceptibility to the TTSS-deficient hrpX mutant of Xoo , indicating that XopP had the abilities to inhibit PAMPs-triggered immunity (PTI) inside plant cells. Interestingly, PR gene expression induced by the chitin elicitor was blocked in suspension-cultured rice cell expressing XopP . Furthermore, we found that XopP interacts with ARM repeating protein containing U-box domain. The role of target factor of XopP in PTI will be discussed.
