Metabolome and transcriptome analysis reveal molecular response to drought stress in indica rice Fuxiangzhan

Drought is one of the most significant factors affecting agricultural production. In this study, the physiological indexes, hormone metabolites, and gene expression regulation network of drought response were analyzed for the high grain quality fragrant rice Fuxiangzhan. After drought stress, Fuxiangzhan exhibited higher drought survival rates and antioxidant enzyme activity compared to restorer lines Minghui63, Minghui86, and the drought-sensitive line Lijiangxintuanheigu, while showing lower membrane iron leakage and less peroxide accumulation. Five hormone metabolites (IAA, ICA, ABA, cZ, and SA) increased, whereas 11 hormone metabolites, including tZ, DHZ, GA1, and JA, decreased. A total of 6118 differentially expressed genes (DEGs) were identified, including 2615 up-regulated and 3503 down-regulated genes, which are involved in biological processes such as photosynthesis, energy metabolism, transcriptional regulation, REDOX, and ion binding, as well as molecular functions related to amino acids, sugars, fatty acids, hormones, and other anabolic metabolism and plant hormone signal transduction. KEGG pathways involving plant hormone signal transduction, zein biosynthesis, carotenoid biosynthesis, and tryptophan metabolism were identified from hormone metabolites and transcriptome analysis. Differentially expressed gene regulatory networks of the four pathways were constructed. The expression levels of 28 drought response genes related to transcription factors, antioxidant enzymes, and osmotic regulation were all up-regulated after drought stress in Fuxiangzhan. Our conclusion is that the hormone levels in Fuxiangzhan change after drought stress. The expression of anti-stress genes, including transcription factors, antioxidant system genes, osmoregulation, and other drought tolerance genes, were up-regulated. These changes lead to alterations in the activity of antioxidant enzymes and other physiological indexes. These results are helpful for further exploration of drought-resistant genes and serve in rice drought resistance breeding.