Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong.
College of Pharmacy, Shaanxi Qinling Application and Development and Engineering Center of Chinese Herbal Medicine, Shaanxi University of Chinese Medicine, Xi'an, China.
Plant J. 2019 Nov;100(4):768-783. doi: 10.1111/tpj.14476. Epub 2019 Sep 3.
Perturbation of the cellular redox state by stress conditions is sensed by redox-sensitive proteins so that the cell can physiologically respond to stressors. However, the mechanisms linking sensing to response remain poorly understood in plants. Here we report that the transcription factor bZIP68 underwent in vivo oxidation in Arabidopsis cells under oxidative stress which is dependent on its redox-sensitive Cys320 residue. bZIP68 is primarily localized to the nucleus under normal growth conditions in Arabidopsis seedlings. Oxidative stress reduces its accumulation in the nucleus and increases its cytosolic localization. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) revealed that bZIP68 primarily binds to promoter regions containing the core G-box (CACGTG) or G-box-like motif of the genes involved in abiotic and biotic stress responses, photosynthesis, biosynthetic processes, and transcriptional regulation. The bzip68 mutant displayed slower growth under normal conditions but enhanced tolerance to oxidative stress. The results from the ChIP-seq and phenotypic and transcriptome comparison between the bzip68 mutant and wildtype indicate that bZIP68 normally suppresses expression of stress tolerance genes and promotes expression of growth-related genes, whereas its inactivation enhances stress tolerance but suppresses growth. bZIP68 might balance stress tolerance with growth through the extent of its oxidative inactivation according to the environment.
应激条件下细胞氧化还原状态的改变被氧化还原敏感蛋白感知，从而使细胞能够对胁迫因子做出生理响应。然而，在植物中，将感应与响应联系起来的机制仍知之甚少。在这里，我们报告在拟南芥细胞中，转录因子 bZIP68 在氧化应激下发生体内氧化，这依赖于其氧化还原敏感的 Cys320 残基。bZIP68 在拟南芥幼苗的正常生长条件下主要定位于细胞核内。氧化应激会减少其在核内的积累并增加其在细胞质中的定位。染色质免疫沉淀测序（ChIP-seq）显示，bZIP68 主要与参与非生物和生物胁迫反应、光合作用、生物合成过程和转录调控的基因的启动子区域结合，这些区域包含核心 G 框（CACGTG）或 G 框样基序。bzip68 突变体在正常条件下生长缓慢，但对氧化应激的耐受性增强。ChIP-seq 以及 bzip68 突变体和野生型之间表型和转录组比较的结果表明，bZIP68 通常抑制应激耐受基因的表达，促进与生长相关基因的表达，而其失活增强应激耐受但抑制生长。bZIP68 可能根据环境通过其氧化失活的程度来平衡应激耐受性与生长。
