State Key Laboratory of Wheat and Maize Crop Science, Center for Crop Genome Engineering, Longzi Lake Campus, College of Agronomy, Henan Agricultural University, Zhengzhou 450046, China.
Key Laboratory of Biology and Genetic Improvement of Maize in Southwest Region, Ministry of Agriculture, Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
Int J Mol Sci. 2022 May 27;23(11):6017. doi: 10.3390/ijms23116017.
Heat stress (HS) seriously restricts the growth and development of plants. When plants are exposed to extreme high temperature, the heat stress response (HSR) is activated to enable plants to survive. Sessile plants have evolved multiple strategies to sense and cope with HS. Previous studies have established that PHYTOCHROME INTERACTING FACTOR 4 (PIF4) acts as a key component in thermomorphogenesis; however, whether PIF4 regulates plant thermotolerance and the molecular mechanism linking this light transcriptional factor and HSR remain unclear. Here, we show that the overexpression of indeed provides plants with a stronger basal thermotolerance and greatly improves the survival ability of under severe HS. Via phylogenetic analysis, we identified two sets (six) of PIF4 homologs in wheat, and the expression patterns of the PIF4 homologs were conservatively induced by heat treatment in both wheat and . Furthermore, the PIF4 protein was accumulated under heat stress and had an identical expression level. Additionally, we found that the core regulator of HSR, HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2), was highly responsive to light and heat. Followed by promoter analysis and ChIP-qPCR, we further found that PIF4 can bind directly to the G-box motifs of the promoter. Via effector-reporter assays, we found that PIF4 binding could activate gene expression, thereby resulting in the activation of other HS-inducible genes, such as heat shock proteins. Finally, the overexpression of led to a stronger basal thermotolerance under non-heat-treatment conditions, thereby resulting in an enhanced tolerance to severe heat stress. Taken together, our findings propose that PIF4 is linked to heat stress signaling by directly binding to the promoter and triggering the HSR at normal temperature conditions to promote the basal thermotolerance. These functions of PIF4 provide a candidate direction for breeding heat-resistant crop cultivars.
热应激（HS）严重限制了植物的生长和发育。当植物暴露在极端高温下时，热应激反应（HSR）被激活，使植物能够存活。固着植物已经进化出多种策略来感知和应对 HS。先前的研究已经确定 PHYTOCHROME INTERACTING FACTOR 4（PIF4）作为热形态发生的关键组成部分；然而，PIF4 是否调节植物耐热性以及将这种光转录因子与 HSR 联系起来的分子机制尚不清楚。在这里，我们表明过表达确实为植物提供了更强的基础耐热性，并大大提高了在严重 HS 下的生存能力。通过系统发育分析，我们在小麦中鉴定了两组（六组）PIF4 同源物，并且在小麦和中，PIF4 同源物的表达模式受到热处理的保守诱导。此外，PIF4 蛋白在热应激下积累，并且具有相同的表达水平。此外，我们发现 HSR 的核心调节剂 HEAT SHOCK TRANSCRIPTION FACTOR A2（HSFA2）对光和热高度响应。通过启动子分析和 ChIP-qPCR，我们进一步发现 PIF4 可以直接结合到的 G 框基序。通过效应物报告基因测定，我们发现 PIF4 结合可以激活基因表达，从而激活其他热诱导基因，如热休克蛋白。最后，过表达导致在非热处理条件下具有更强的基础耐热性，从而增强了对严重热应激的耐受性。总之，我们的研究结果表明，PIF4 通过直接结合启动子并在常温条件下触发 HSR 来连接到热应激信号，从而促进基础耐热性。PIF4 的这些功能为培育耐热作物品种提供了一个候选方向。
