The XA21::EFR Chimeric Receptor Recognizes RaxX and Confers Resistance to Xanthomonas Infection
N. THOMAS (1), N. Oksenberg (1), B. Schwessinger (1), Y. Ngyuen (1), P. Ronald (1) (1) UC Davis, U.S.A.

The full length XA21 protein confers robust resistance to Xanthomonas oryzae pv. oryzae (Xoo). Previous studies with chimeric immune receptor proteins indicate that the cytoplasmic domains of plant receptors dictate downstream signaling and host resistance. However, transgenic rice plants expressing the EFR::XA21 chimeric receptor, containing the ectodomian of the Arabidopsis EFR immune receptor and the XA21 cytoplasmic domain, are not resistant to Xoo infection with highly virulent strains (Schwessinger et al. 2015). Here, we test if the XA21 ectodomain dictates the disease resistance outcome to Xoo. We produced transgenic rice expressing XA21::EFR, containing the XA21 ectodomain fused to the EFR cytoplasmic domain. We determined XA21::EFR rice are resistant to Xoo and respond to the XA21 elicitor, RaxX (Pruitt et al. 2015), by producing reactive oxygen species and highly expressing stress-related genes. These results suggest that the XA21 ectodomain is critical for conferring XA21-mediated immunity to Xoo by perceiving RaxX, while the cytoplasmic domain can be replaced with the EFR cytoplasmic domain. Our results challenge the concept that cytoplasmic domains dictate host resistance and give new insight into how XA21 confers robust resistance to Xoo.

Abstract Number: P17-627
Session Type: Poster