Table_1_Type-A response regulators negatively mediate heat stress response by altering redox homeostasis in Arabidopsis.xlsx

Besides the long-standing role of cytokinins (CKs) as growth regulators, their current positioning at the interface of development and stress responses is coming into recognition. The current evidence suggests the notion that CKs are involved in heat stress response (HSR), however, the role of CK signaling components is still elusive. In this study, we have identified a role of the CK signaling components type-A Arabidopsis response regulators (ARRs) in HSR in Arabidopsis. The mutants of multiple type-A ARR genes exhibit improved basal and acquired thermotolerance and, altered response to oxidative stress in our physiological analyses. Through proteomics profiling, we show that the type-A arr mutants experience a ‘stress-primed’ state enabling them to respond more efficiently upon exposure to real stress stimuli. A substantial number of proteins that are involved in the heat-acclimatization process such as the proteins related to cellular redox status and heat shock, are already altered in the type-A arr mutants without a prior exposure to stress conditions. The metabolomics analyses further reveal that the mutants accumulate higher amounts of α-and γ-tocopherols, which are important antioxidants for protection against oxidative damage. Collectively, our results suggest that the type-A ARRs play an important role in heat stress response by affecting the redox homeostasis in Arabidopsis.

除细胞分裂素（cytokinins, CKs）作为生长调节剂的经典功能外，其作为生长发育与胁迫响应之间关键调控枢纽的作用正逐渐获得学界认可。现有研究证据表明，细胞分裂素参与热胁迫响应（heat stress response, HSR），但目前细胞分裂素信号组分的具体功能仍有待阐明。本研究明确了细胞分裂素信号组分——A型拟南芥反应调节因子（type-A Arabidopsis response regulators, ARRs）在拟南芥热胁迫响应中的功能。生理分析结果显示，多重A型ARR基因突变体的基础热耐受性与获得性热耐受性均得到提升，且其氧化胁迫响应模式发生改变。通过蛋白质组学分析，本研究发现A型arr突变体处于“胁迫预适应”状态，使其在遭遇实际胁迫刺激时能更高效地做出响应。在未预先经历胁迫的情况下，该类突变体中已有大量参与热驯化过程的蛋白质表达量发生改变，其中包括与细胞氧化还原状态、热休克相关的蛋白。代谢组学分析进一步显示，该类突变体可积累更多的α-和γ-生育酚，而此类物质是抵御氧化损伤的关键抗氧化成分。综上，本研究结果表明，A型ARRs通过调控拟南芥的氧化还原稳态，在热胁迫响应中发挥重要功能。