Kumimoto Roderick W, Ellison Cory T, Toruño Tania Y, Bak Aurélie, Zhang Hongtao, Casteel Clare L, Coaker Gitta, Harmer Stacey L
Department of Plant Biology, University of California, Davis, Davis, CA, United States.
Department of Plant Pathology, University of California, Davis, Davis, CA, United States.
Front Plant Sci. 2021 Oct 1;12:707923. doi: 10.3389/fpls.2021.707923. eCollection 2021.
Numerous links have been reported between immune response and DNA damage repair pathways in both plants and animals but the precise nature of the relationship between these fundamental processes is not entirely clear. Here, we report that XAP5 CIRCADIAN TIMEKEEPER (XCT), a protein highly conserved across eukaryotes, acts as a negative regulator of immunity in and plays a positive role in responses to DNA damaging radiation. We find mutants have enhanced resistance to infection by a virulent bacterial pathogen, pv. DC3000, and are hyper-responsive to the defense-activating hormone salicylic acid (SA) when compared to wild-type. Unlike most mutants with constitutive effector-triggered immunity (ETI), plants do not have increased levels of SA and retain enhanced immunity at elevated temperatures. Genetic analysis indicates acts independently of (), which encodes a known SA receptor. Since DNA damage has been reported to potentiate immune responses, we next investigated the DNA damage response in our mutants. We found seedlings to be hypersensitive to UV-C and γ radiation and deficient in phosphorylation of the histone variant H2A.X, one of the earliest known responses to DNA damage. These data demonstrate that loss of causes a defect in an early step of the DNA damage response pathway. Together, our data suggest that alterations in DNA damage response pathways may underlie the enhanced immunity seen in mutants.
在植物和动物中，免疫反应与DNA损伤修复途径之间已报道了许多联系，但这些基本过程之间关系的确切性质尚不完全清楚。在此，我们报道了XAP5生物钟蛋白（XCT），一种在真核生物中高度保守的蛋白质，在植物中作为免疫的负调节因子，并在对DNA损伤辐射的反应中发挥积极作用。我们发现XCT突变体对毒性细菌病原体丁香假单胞菌番茄致病变种DC3000的感染具有增强的抗性，并且与野生型相比，对防御激活激素水杨酸（SA）超敏感。与大多数具有组成型效应子触发免疫（ETI）的突变体不同，XCT突变体植物的SA水平没有增加，并且在高温下仍保持增强的免疫力。遗传分析表明，XCT的作用独立于NPR1（NPR1编码一种已知的SA受体）。由于据报道DNA损伤可增强免疫反应，我们接下来研究了我们突变体中的DNA损伤反应。我们发现XCT幼苗对UV-C和γ辐射超敏感，并且组蛋白变体H2A.X的磷酸化缺陷，H2A.X是已知最早的DNA损伤反应之一。这些数据表明，XCT的缺失导致DNA损伤反应途径早期步骤中的缺陷。总之，我们的数据表明，DNA损伤反应途径的改变可能是XCT突变体中增强免疫力的基础。
