Protein ubiquitination is critical for various biological processes in eukaryotes. A ubiquitin (Ub) chain can be linked through one of the seven lysine (K) residues or the N-terminus methionine of the Ub, and the Ub-conjugating enzymes called E2s play a critical role in determining the linkage specificity of Ub chains. Further, while K48-linked polyubiquitin chain is important for protein degradation, much less is known about the functions of other types of polyubiquitin chains in plants. We showed previously that UBC22 is unique in its ability to catalyze K11-dependent Ub dimer formation in vitro and ubc22 knockout mutants had defects in megasporogenesis. In this study, further analyses of the Arabidopsis ubc22 mutants revealed four subtypes of plants based on the phenotypic changes in vegetative growth. These four subtypes appeared consistently in the plants of three independent ubc22 mutants. Transcriptomic analysis showed that transcript levels of genes related to several pathways were altered differently in different subtypes of mutant plants. In one subtype, the mutant plants had increased expression of genes related to plant defenses and showed enhanced resistance to a necrotrophic plant pathogen. These results suggest multiple functions of UBC22 during plant development and stress response.

中文翻译：

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拟南芥 UBC22，一种能够催化赖氨酸 11 特异性泛素连接形成的 E2，在植物生长和免疫中具有多种功能

蛋白质泛素化对于真核生物的各种生物过程至关重要。泛素 (Ub) 链可以通过七个赖氨酸 (K) 残基之一或 Ub 的 N 端蛋氨酸连接，并且称为 E2s 的 Ub 结合酶在确定 Ub 链的连接特异性方面起着关键作用。此外，虽然 K48 连接的聚泛素链对蛋白质降解很重要，但对植物中其他类型的聚泛素链的功能知之甚少。我们之前表明 UBC22 在体外催化 K11 依赖性 Ub 二聚体形成的能力方面是独一无二的，并且 ubc22 敲除突变体在大孢子发生方面存在缺陷。在这项研究中，对拟南芥 ubc22 突变体的进一步分析揭示了基于营养生长表型变化的四种植物亚型。这四种亚型一致出现在三个独立的 ubc22 突变体的植物中。转录组学分析表明，在突变植物的不同亚型中，与几种途径相关的基因的转录水平发生了不同的改变。在一个亚型中，突变植物与植物防御相关的基因表达增加，并且对坏死性植物病原体的抗性增强。这些结果表明 UBC22 在植物发育和胁迫响应过程中具有多种功能。突变植物增加了与植物防御相关基因的表达，并显示出对坏死性植物病原体的抗性增强。这些结果表明 UBC22 在植物发育和胁迫响应过程中具有多种功能。突变植物增加了与植物防御相关基因的表达，并显示出对坏死性植物病原体的抗性增强。这些结果表明 UBC22 在植物发育和胁迫响应过程中具有多种功能。