摘要The rice pattern recognition receptor (PRR) XA21 confers race-specific resistance in leaf infection by bacterial blight Xathomonas oryzae pv.oryzae (Xoo),and was shown to be primarily localized to the endoplasmic reticulum (ER) when expressed with its native promoter or overexpressed in the protoplast.However,whether the protein is still ERlocalization in the intact cell when overexpressed remains to be identified.Here,we showed that XA21,its kinase-dead mutant XA21PK736EP and the triple autophosphorylation mutant XA21Ps686A/T688A/s699A GFP fusions were primarily localized to the plasma membrane (PM) when overexpressed in the intact transgenic rice cell,and also localized to the ER in the SCAMP-positive early endosomal compartment in the protoplast,suggesting that XA21 might be endocytosed to initiate resistance responses during pathogen infection.We also established a root infection system and demonstrated that XA21 also mediated race-specific resistance responses to Xoo in the root.Our current study provides an insight into the nature of the XA21-mediated resistance and a practical approach using the root cell system to further dissect the cellular signaling of the PRR during the rice-Xoo interaction.