Jiangsu Key Laboratory of Crop Genetics and Physiology/Jiangsu Key Laboratory of Crop Cultivation and Physiology/Agricultural College of Yangzhou University, Yangzhou, 225009, People's Republic of China.
Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou, 225009, People's Republic of China.
BMC Plant Biol. 2022 Sep 9;22(1):432. doi: 10.1186/s12870-022-03822-3.
Salicylic acid (SA) is a phytohormone which works to regulate the abiotic stress response of plants. However, the molecular mechanism by which SA mediates heat tolerance in waxy maize (Zea mays L. sinsensis Kulesh) remains unknown.
Two varieties of waxy maize seedlings, heat-tolerant 'Yunuo7' (Y7) and heat-sensitive 'Suyunuo5' (S5), were pretreated with SA prior to heat stress (HTS). After treatment, physiological and transcriptomic changes were analyzed. Compared with HTS, the exogenous application of SA enhanced the shoot dry weight, the activities of antioxidant enzymes (e.g., SOD, POD, CAT and APX), and the concentration of endogenous phytohormones (e.g., SA, ABA, IAA, GA3), while decreased the MDA content. Transcriptome analysis showed that the number of differentially expressed genes (DEGs) identified in the control (CK) vs HTS and HTS vs HTS + SA comparisons were more in S5 than in Y7. HTS induced the downregulation of genes involved in photosynthesis and the upregulation of genes encoding heat shock transcription factors (HSFs) and heat shock proteins (HSPs). Compared with HTS, SA pretreatment reversed the expression of 5 photosynthesis-related genes, 26 phytohormone-related genes, and all genes encoding HSFs and HSPs in S5. Furthermore, the number of alternative splicing (AS) events increased under HTS treatment for both varieties, while decreased under SA pretreatment of S5. Differentially spliced genes (DSGs) showed little overlap with DEGs, and DEGs and DSGs differed significantly in functional enrichment.
Physiological and transcriptional together indicated that HTS and SA pretreatment had a greater effect on S5 than Y7. Additionally, it appears that transcriptional regulation and AS work synergistically to enhance thermotolerance in heat-sensitive waxy maize. Our study revealed the regulatory effects and underlying molecular mechanisms of SA on waxy maize seedling under HTS.
水杨酸（SA）是一种植物激素，可调节植物的非生物胁迫反应。然而，SA 介导蜡质玉米（Zea mays L. sinsensis Kulesh）耐热性的分子机制尚不清楚。
用 SA 预处理耐热品种‘云糯 7 号’（Y7）和热敏品种‘绥糯 5 号’（S5）的蜡质玉米幼苗，然后进行热胁迫（HTS）处理。处理后，分析生理和转录组变化。与 HTS 相比，外源施用 SA 提高了茎干重、抗氧化酶（如 SOD、POD、CAT 和 APX）的活性和内源性植物激素（如 SA、ABA、IAA、GA3）的浓度，同时降低了 MDA 含量。转录组分析表明，在 CK 与 HTS 以及 HTS 与 HTS+SA 比较中，S5 中鉴定的差异表达基因（DEGs）数量多于 Y7。HTS 诱导与光合作用相关的基因下调，与热休克转录因子（HSFs）和热休克蛋白（HSPs）编码相关的基因上调。与 HTS 相比，SA 预处理逆转了 S5 中 5 个光合作用相关基因、26 个植物激素相关基因以及所有 HSFs 和 HSPs 基因的表达。此外，两种品种在 HTS 处理下的可变剪接（AS）事件数量增加，而 S5 在 SA 预处理下的 AS 事件数量减少。差异剪接基因（DSGs）与差异表达基因（DEGs）的重叠较少，DEGs 和 DSGs 在功能富集方面存在显著差异。
生理和转录组分析表明，HTS 和 SA 预处理对 S5 的影响大于 Y7。此外，转录调控和 AS 似乎协同作用，增强了热敏蜡质玉米的耐热性。本研究揭示了 SA 在 HTS 下对蜡质玉米幼苗的调节作用及其潜在的分子机制。
