Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
The Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath BA2 7AY, UK.
Cell Host Microbe. 2023 Jun 14;31(6):949-961.e5. doi: 10.1016/j.chom.2023.04.009. Epub 2023 May 10.
White blister rust, caused by the oomycete Albugo candida, is a widespread disease of Brassica crops. The Brassica relative Arabidopsis thaliana uses the paired immune receptor complex CSA1-CHS3/DAR4 to resist Albugo infection. The CHS3/DAR4 sensor NLR, which functions together with its partner, the helper NLR CSA1, carries an integrated domain (ID) with homology to DA1 peptidases. Using domain swaps with several DA1 homologs, we show that the LIM-peptidase domain of the family member CHS3/DAR4 functions as an integrated decoy for the family member DAR3, which interacts with and inhibits the peptidase activities of the three closely related peptidases DA1, DAR1, and DAR2. Albugo infection rapidly lowers DAR3 levels and activates DA1 peptidase activity, thereby promoting endoreduplication of host tissues to support pathogen growth. We propose that the paired immune receptor CSA1-CHS3/DAR4 detects the actions of a putative Albugo effector that reduces DAR3 levels, resulting in defense activation.
白疱锈病由卵菌门白锈菌引起，广泛发生于十字花科作物上。十字花科近缘植物拟南芥利用配对免疫受体复合物 CSA1-CHS3/DAR4 抵抗白锈菌感染。CHS3/DAR4 传感器 NLR 与其伙伴 CSA1 共同作用，携带与 DA1 肽酶同源的整合结构域（ID）。通过与几个 DA1 同源物的结构域交换，我们发现家族成员 CHS3/DAR4 的 LIM 肽酶结构域可作为家族成员 DAR3 的整合诱饵，DAR3 与三个密切相关的肽酶 DA1、DAR1 和 DAR2 相互作用并抑制其肽酶活性。白锈菌感染迅速降低 DAR3 水平并激活 DA1 肽酶活性，从而促进宿主组织的内复制，以支持病原体生长。我们提出，配对免疫受体 CSA1-CHS3/DAR4 检测到一种假定的白锈菌效应物的作用，该效应物降低 DAR3 水平，从而导致防御激活。
