拟南芥中CHC1或CHC2的功能丧失导致自噬缺陷并造成免疫激活

Loss of CHC1 or CHC2 in Arabidopsis compromises autophagy pathway and leads to enhanced disease resistance

摘要:

拟南芥网格蛋白轻链2 (clathrin light chain 2, CLC2)和CLC3功能丧失会造成自噬缺陷，从而导致植物抗病性增强。为了探究网格蛋白重链(clathrin heavy chain, CHC)是否发挥与CLCs类似的作用，本研究结合遗传学、细胞生物学及抗性分析探究了CHC在自噬途径以及在自噬相关免疫调控中的作用。结果发现，CHC1或CHC2的功能丧失会加速暗处理诱导的衰老进程，表现出自噬途径缺陷相关的典型早衰表型，表明自噬途径可能受到损伤。与此一致，在自噬诱导条件下chc1-2和chc2-2突变体中自噬小体数量显著减少，进一步证实其自噬通量下降。抗性分析表明，chc1-2和chc2-2突变体对菊科白粉病菌(Golovinomyces cichoracearum)表现出增强的抗性，抗性的增强与活性氧(reactive oxygen species, ROS)过量积累以及胼胝质沉积增强密切相关。以上结果表明CHC的完整功能对维持正常自噬途径至关重要，CHC缺失通过破坏自噬稳态触发免疫激活。本研究为通过调控自噬途径改良作物抗病性提供了理论依据。

Abstract:

We have previously showed that loss of clathrin light chain (CLC) 2 and CLC3 in Arabidopsis simultaneously impairs autophagy pathway, thereby resulting in enhanced disease resistance. To understand whether clathrin heavy chain (CHC) proteins play similar roles as CLCs, we used combined approaches of genetics, cell biology, and resistance assays to investigate the roles of CHCs in the autophagy pathway and in autophagy-related immunity. The results showed that the loss of either CHC1 or CHC2 accelerated dark-induced senescence, a hallmark phenotype of defective autophagy, suggesting that the autophagy pathway may be impaired. Consistent with this phenotype, the number of autophagosomes induced under dark treatment conditions was significantly reduced in both chc1-2 and chc2-2 mutants, which indicated that the autophagic flux was significantly reduced in both mutants. The disease resistance assay showed that both mutants exhibited enhanced resistance to the fungal pathogen Golovinomyces cichoracearum, which was highly correlated with elevated reactive oxygen species (ROS) accumulation and increased callose deposition. Together, these findings reveal that CHC-dependent functions are required for efficient autophagy and disruption of clathrin-mediated trafficking leads to the activation of plant immune responses due to an impaired autophagy pathway. This study provides a theoretical basis to enhance disease resistance in crops through manipulation of autophagy pathway.