Poly(ADP-ribosyl)ation (PARylation) is a posttranslational modification reversibly catalyzed by poly(ADP-ribose) polymerases (PARPs) and poly(ADP-ribose) glycohydrolases (PARGs) and plays a key role in multiple cellular processes. The molecular mechanisms by which PARylation regulates innate immunity remain largely unknown in eukaryotes. Here we show that Arabidopsis UBC13A and UBC13B, the major drivers of lysine 63 (K63)-linked polyubiquitination, directly interact with PARPs/PARGs. Activation of pathogen-associated molecular pattern (PAMP)-triggered immunity promotes these interactions and enhances PARylation of UBC13. Both parp1 parp2 and ubc13a ubc13b mutants are compromised in immune responses with increased accumulation of total pathogenesis-related (PR) proteins but decreased accumulation of secreted PR proteins. Protein disulfide-isomerases (PDIs), essential components of endoplasmic reticulum quality control (ERQC) that ensure proper folding and maturation of proteins destined for secretion, complex with PARPs/PARGs and are PARylated upon PAMP perception. Significantly, PARylation of UBC13 regulates K63-linked ubiquitination of PDIs, which may further promote their disulfide isomerase activities for correct protein folding and subsequent secretion. Taken together, these results indicate that plant immunity is coordinately regulated by PARylation and K63-linked ubiquitination.

聚 (ADP-核糖) 化 (PARylation) 是一种由聚 (ADP-核糖) 聚合酶 (PARP) 和聚 (ADP-核糖) 糖水解酶 (PARG) 可逆催化的翻译后修饰，在多个细胞过程中起关键作用。PARylation 调节先天免疫的分子机制在真核生物中仍然很大程度上未知。在这里，我们显示拟南芥 UBC13A 和 UBC13B，赖氨酸 63 (K63) 连接的多泛素化的主要驱动因素，直接与 PARPs/PARGs 相互作用。激活病原体相关分子模式 (PAMP) 触发的免疫可促进这些相互作用并增强 UBC13 的 PARylation。parp1 parp2和ubc13a ubc13b突变体在免疫反应中受到损害，总发病机制相关 (PR) 蛋白的积累增加，但分泌的 PR 蛋白的积累减少。蛋白质二硫键异构酶 (PDI) 是内质网质量控制 (ERQC) 的重要组成部分，可确保用于分泌的蛋白质的正确折叠和成熟，与 PARPs/PARGs 复合并在 PAMP 感知时被 PAR 化。重要的是，UBC13 的 PARylation 调节了 PDI 的 K63 连接的泛素化，这可能会进一步促进它们的二硫键异构酶活性，以实现正确的蛋白质折叠和随后的分泌。总之，这些结果表明植物免疫受到 PARylation 和 K63 连接的泛素化的协调调节。