A Xanthomonas oryzae pv. oryzae effector, XopR, associates with receptor-like cytoplasmic kinases and suppresses PAMP-triggered stomatal closure

Abstract

Receptor-like kinases (RLKs) play important roles in plant immunity signaling; thus, many are hijacked by pathogen effectors to promote successful pathogenesis. Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice leaf blight disease. The strain PXO99A has 18 non-TAL (transcription activation-like) effectors; however, their mechanisms of action and host target proteins remain largely unknown. Although the effector XopR from the Xoo strain MAFF311018 was shown to suppress PAMP-triggered immune responses in Arabidopsis, its target has not yet been identified. Here, we show that PXO99A XopR interacts with BIK1 at the plasma membrane. BIK1 is a receptor-like cytoplasmic kinase (RLCK) belonging to the RLK family of proteins and mediates PAMP-triggered stomatal immunity. In turn, BIK1 phosphorylates XopR. Furthermore, XopR suppresses PAMP-triggered stomatal closure in transgenic Arabidopsis expressing XopR. In addition, XopR is able to associate with RLCKs other than BIK1. These results suggest that XopR likely suppresses plant immunity by targeting BIK1 and other RLCKs. Xanthomonas, effector, XopR, BIK1, immunity Citation:Wang, S., Sun, J., Fan, F., Tan, Z., Zou, Y., and Lu, D. (2016). A Xanthomonas oryzae pv. oryzae effector, XopR, associates with receptor-like cytoplasmic kinases and suppresses PAMP-triggered stomatal closure. Sci China Life Sci 59, 897 -905.

The Xanthomonas effector XopK harbours E3 ubiquitin‐ligase activity that is required for virulence

“…oryzae full virulence and for suppressing basal defence in N. benthamiana (Song & Yang, 2010), while XopR was found to contribute to X. oryzae pv. oryzae virulence in rice (Akimoto-Tomiyama et al, 2012) and to target BIK1 and its related receptor-like cytoplasmic kinases (RLCKs) to suppress flg22-induced stomatal closure in Arabidopsis (Wang et al, 2016). It is conceivable that XopR also targets the rice homologue of BIK1 to interfere with rice immunity; however, this has yet to be demonstrated.…”

Stomatal Defense a Decade Later

“…The XopR effector from Xanthomonas oryzae pv oryzae strain PXO99A also inhibits flg22-induced stomatal closure; however, the mechanism remains elusive (Wang et al, 2016).…”

Identification of critical cysteine sites in brassinosteroid‐insensitive 1 and novel signaling regulators using a transient expression system

“…To understand the underlying mechanism of the effects of Cys‐411 mutation on BRI1's function, we analyzed the subcellular localization of BRI1C411A fused to a GFP tag (BRI1C411A‐GFP). When transiently expressed in Arabidopsis protoplasts, the localization of XopR‐GFP, a Xanthomonas oryzae pv oryzae ( Xoo ) effector protein localized to the PM in plant cell (Wang et al ., ), overlaps with that of TaPBS1‐RFP, also a PM‐localized protein (Sun J. et al ., ). Similarly, the localization of WT BRI1‐GFP overlaps with that of TaPBS1‐RFP, whereas the majority of BRI1C411A‐GFP was no longer localized to the PM (Fig.…”

“…Full-length BES1, BIN2, BSU1, CDG1, BSK1, PCRK1, and PCRK2 were amplified by reverse transcription PCR from Col-0 RNA and each was cloned into a plant expression vector fused to a tag like HA, FLAG, Myc, green fluorescence protein (GFP), or the carboxyl-terminal half of YFP (cYFP). XopR-GFP was reported previously (Wang et al, 2016). Triticum aestivum AVRPPHB SUSCEPTIBLE1 (TaPBS1) was subcloned into a plant expression vector fused to a red fluorescence protein (RFP) tag .…”

“…New Phytologist GFP). When transiently expressed in Arabidopsis protoplasts, the localization of XopR-GFP, a Xanthomonas oryzae pv oryzae (Xoo) effector protein localized to the PM in plant cell (Wang et al, 2016), overlaps with that of TaPBS1-RFP, also a PM-localized protein . Similarly, the localization of WT BRI1-GFP overlaps with that of TaPBS1-RFP, whereas the majority of BRI1C411A-GFP was no longer localized to the PM (Fig.…”