Plasma Membrane Localization and Potential Endocytosis of Constitutively Expressed XA21 Proteins in Transgenic Rice

4.296
Fang Chen, Ming-Jun Gao, Yan-Song Miao, Yue-Xing Yuan, Mu-Yang Wang, Qun Li, Bi-Zeng Mao, Li-Wen Jiang, Zu-Hua He
Molecular Plant, 2010, 3(5): 917-926  DOI: 10.1093/mp/ssq038     追溯原文......本站官方QQ群:62473826
Rice; XA21; pattern recognition receptor; bacterial bight cellular localization; internalization; root infection; race-specific resistance

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 ER-localization 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 transgenic protoplast. The transgenic plants constitutively expressing the wild-type XA21 or its GFP fusion displayed race-specific resistance to Xoo at the adult and seedling stages. XA21 and XA21PK736EP could be internalized probably via 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.

转基因水稻中,组成性表达的XA21蛋白的质膜定位以及潜在的胞吞作用

当叶片被白叶枯病菌Xoo侵染时,水稻模式识别受体(PRR)XA21提供小种专化抗性,当在原生质体中利用自身启动子驱动表达或者过表达时,XA21主要定位在内质网上(ER)。但是过表达时,这个蛋白在完整细胞中是否还是ER定位则仍不清楚。本文中我们发现,在转基因水稻完整细胞中,XA21激酶失活突变形式XA21PK736EP以及自体三磷酸化突变形式XA21PS686A/T688A/S699A融合GFP蛋白主要定位在质膜(PM)上,在转基因原生质体则定位在ER上。组成性表达野生型XA21或者它的GFP融合蛋白的转基因植株在成熟期和苗期会表现出对Xoo的小种专化抗性。在原生质体中,XA21和XA21PK736EP能够被内化,这可能通过SCAMP正向早期的内体实现,表明在病原菌侵染时,XA21可能发生胞吞作用,进而引起防卫反应。我们还建立了根侵染系统,表明在根中XA21也能够介导对Xoo的小种特异防卫反应。我们的研究为理解自然条件下XA21介导的抗病性提供了新的观点,并构建了一套有效方法利用根系统进一步分析Xoo侵染水稻时细胞内的PRR信号。


基因列表
  白叶枯病抗性基因 Xa21; Xa-21