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Flavonoids are a class of key polyphenolic secondary metabolites with broad functions in plants, including stress defense, growth, development and reproduction. Oryza sativa L. (rice) is a well-known model plant for monocots, with a wide range of flavonoids, but the key flavonoid biosynthesis-related genes and their molecular features in rice have not been comprehensively and systematically characterized. Here, we identified 85 key structural gene candidates associated with flavonoid biosynthesis in the rice genome. They belong to 13 families potentially encoding chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonol synthase (FLS), leucoanthocyanidin dioxygenase (LDOX), anthocyanidin synthase (ANS), flavone synthase II (FNSII), flavanone 2-hydroxylase (F2H), flavonoid 3′-hydroxylase (F3′H), flavonoid 3′,5′-hydroxylase (F3′5′H), dihydroflavonol 4-reductase (DFR), anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR). Through structural features, motif analyses and phylogenetic relationships, these gene families were further grouped into five distinct lineages and were examined for conservation and divergence. Subsequently, 22 duplication events were identified out of a total of 85 genes, among which seven pairs were derived from segmental duplication events and 15 pairs were from tandem duplications, demonstrating that segmental and tandem duplication events play important roles in the expansion of key flavonoid biosynthesis-related genes in rice. Furthermore, these 85 genes showed spatial and temporal regulation in a tissue-specific manner and differentially responded to abiotic stress (including six hormones and cold and salt treatments). RNA-Seq, microarray analysis and qRT-PCR indicated that these genes might be involved in abiotic stress response, plant growth and development. Our results provide a valuable basis for further functional analysis of the genes involved in the flavonoid biosynthesis pathway in rice. [ABSTRACT FROM AUTHOR]

Sugars are critical for plant growth and development as suppliers of carbon and energy, as signal molecules, or as solute molecules for osmotic homeostasis. Monosaccharide transporter (MST) genes are involved in various processes of plant growth and development as well as in response to abiotic stresses. However, the evolution and their roles of MST genes in growth and development and in coping with abiotic stresses in rice are poorly known. Here, we identified 64 MST genes in rice genome, which are classified into seven subfamilies: STP, PLT, AZT, ERD, pGlcT, INT, and XTPH. MST genes are not evenly distributed between chromosomes (Chrs) with a bias to Chr 3, 4, 7, and 11, which could be a result of duplication of fragments harboring MST genes. In total, 12 duplication events were found in the rice MST family, among which, two pairs were derived from fragmental duplications and ten pairs were from tandem duplications. The synonymous and nonsynonymous substitution rates of duplicate gene pairs demonstrated that the MST family was under a strong negative selection during the evolution process. Furthermore, a comprehensive expression analysis conducted in 11 different tissues, three abiotic stresses, five hormone treatments, and three sugar treatments revealed different expression patterns of MST genes and indicated diversified functions of them. Our results suggest that MST genes play important roles not only in various abiotic stresses but also in hormone and sugar responses. The present results will provide a vital insight into the functional divergence of the MST family in the future study. [ABSTRACT FROM AUTHOR]