Exo70B1是外囊复合体的蛋白质亚基,在多种细胞机制中起着至关重要的作用,包括针对病原体的免疫反应。拟南芥(以下简称拟南芥)的钙依赖性激酶5(CPK5),功能破坏后磷酸化AtExo70B1。我们以前报道过,黄单胞菌油菜pv。卷心菜效应子XopP损害AtExo70B1,同时绕过宿主的过敏反应,在某种程度上还不清楚。在这里,我们设计了一种实验方法,其中包括生物物理,生物化学,和分子分析,并基于结构和功能预测,利用AplhaFold和DALI在线服务器,分别,以表征体内XccXopP功能。AtExo70B1和XcXopP之间的相互作用在高温下非常稳定,而AtExo70B1似乎在表达XcXopP的转基因拟南芥上被磷酸化。XccXopP揭示了与已知哺乳动物激酶和在Ser107、Ser111、Ser248、Thr309和Thr364处磷酸化AtExo70B1的相似性。此外,XccXopP保护AtExo70B1免于AtCPK5磷酸化。这些研究结果表明,XccXopP是一种效应子,它不仅在其宿主靶标AtExo70B1上充当新型丝氨酸/苏氨酸激酶,而且还保护后者免受先天的AtCPK5磷酸化,以绕过宿主的免疫反应。数据可通过具有标识符PXD041405的ProteomeXchange获得。
Exo70B1 is a protein subunit of the exocyst complex with a crucial role in a variety of cell mechanisms, including immune responses against pathogens. The calcium-dependent kinase 5 (CPK5) of Arabidopsis thaliana (hereafter Arabidopsis), phosphorylates AtExo70B1 upon functional disruption. We previously reported that, the Xanthomonas campestris pv. campestris effector XopP compromises AtExo70B1, while bypassing the host\'s hypersensitive response, in a way that is still unclear. Herein we designed an experimental approach, which includes biophysical, biochemical, and molecular assays and is based on structural and functional predictions, utilizing AplhaFold and DALI online servers, respectively, in order to characterize the in vivo XccXopP function. The interaction between AtExo70B1 and XccXopP was found very stable in high temperatures, while AtExo70B1 appeared to be phosphorylated at XccXopP-expressing transgenic Arabidopsis. XccXopP revealed similarities with known mammalian kinases and phosphorylated AtExo70B1 at Ser107, Ser111, Ser248, Thr309, and Thr364. Moreover, XccXopP protected AtExo70B1 from AtCPK5 phosphorylation. Together these findings show that XccXopP is an effector, which not only functions as a novel serine/threonine kinase upon its host target AtExo70B1 but also protects the latter from the innate AtCPK5 phosphorylation, in order to bypass the host\'s immune responses. Data are available via ProteomeXchange with the identifier PXD041405.