Seed Priming with 2,4-Epibrassionolide Enhances Seed Germination and Heat Tolerance in Rice by Regulating the Antioxidant System and Plant Hormone Signaling Pathways

With global climate warming, enhancing the heat stress tolerance of rice seeds is critical for ensuring crop yields and maintaining global food security. 2,4-Epibrassionolide (EBR) has been shown to effectively alleviate the adverse effects of heat stress on rice seed germination, but its mitigation mechanism has not been fully clarified. In this experiment, exogenous EBR was used as a seed priming agent. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), malondialdehyde (MDA), soluble protein contents, and plant hormone levels were measured during rice seed germination under heat stress (38 °C). We constructed a cDNA library for transcriptome sequencing analysis. The results showed that exogenous EBR could effectively alleviate the effect of heat stress on rice seeds by enhancing SOD, POD, and CAT enzyme activity; reducing the MDA content; and increasing the soluble protein content. Additionally, exogenous EBR increases the levels of GA and IAA while decreasing the ABA content. According to a transcriptomic analysis, exogenous EBR can induce the expression of key genes involved in GA, IAA, and ABA hormone biosynthesis and metabolism, regulating GA-, IAA-, ABA-, and H2O2-mediated signaling pathways to promote the germination of rice seeds under heat stress. This study provides new insights into the application of rice seed priming techniques.