Temperature shapes the geographical distribution and behavior of plants. Understanding the regulatory mechanisms underlying the plant heat response is important for developing climate-resilient crops, including maize (Zea mays). To identify transcription factors that may contribute to the maize heat response, we generated a dataset of short- and long-term transcriptome changes following a heat treatment time course in the inbred line B73. Co-expression network analysis highlighted several transcription factors, including the class B2a heat shock factor (HSF) ZmHSF20. Zmhsf20 mutant seedlings exhibited enhanced tolerance to heat stress. Furthermore, DNA affinity purification sequencing and Cleavage Under Targets and Tagmentation (CUT&Tag) assays demonstrated that ZmHSF20 binds to the promoters of Cellulose synthase A2 (ZmCesA2) and three class A Hsf genes, including ZmHsf4, repressing their transcription. We showed that ZmCesA2 and ZmHSF4 promote the heat response, with ZmHSF4 directly activating ZmCesA2 transcription. In agreement with the transcriptome analysis, ZmHSF20 inhibited cellulose accumulation and repressed the expression of cell wall–related genes. Importantly, the Zmhsf20 Zmhsf4 double mutant exhibited decreased thermotolerance, placing ZmHsf4 downstream of ZmHsf20. We proposed an expanded model of the heat stress response in maize, whereby ZmHSF20 lowers seedling heat tolerance by repressing ZmHsf4 and ZmCesA2, thus balancing seedling growth and defense.

中文翻译：

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热休克因子 20–HSF4–纤维素合酶 A2 模块调节玉米的热应激耐受性

温度决定植物的地理分布和行为。了解植物热响应的调控机制对于开发包括玉米 (Zea mays) 在内的气候适应型作物非常重要。为了确定可能有助于玉米热反应的转录因子，我们生成了自交系 B73 热处理时间过程后的短期和长期转录组变化的数据集。共表达网络分析强调了几种转录因子，包括 B2a 类热休克因子 (HSF) ZmHSF20。 Zmhsf20 突变体幼苗表现出增强的热应激耐受性。此外，DNA 亲和纯化测序以及靶标切割和标签 (CUT&Tag) 测定表明，ZmHSF20 与纤维素合酶 A2 (ZmCesA2) 和三个 A 类 Hsf 基因（包括 ZmHsf4）的启动子结合，抑制其转录。我们发现ZmCesA2和ZmHSF4促进热反应，其中ZmHSF4直接激活ZmCesA2转录。与转录组分析一致，ZmHSF20 抑制纤维素积累并抑制细胞壁相关基因的表达。重要的是，Zmhsf20 Zmhsf4 双突变体表现出耐热性降低，将 ZmHsf4 置于 ZmHsf20 下游。我们提出了玉米热应激反应的扩展模型，其中ZmHSF20通过抑制ZmHsf4和ZmCesA2来降低幼苗的耐热性，从而平衡幼苗的生长和防御。