title: Transcriptomic analysis of UV-treated rice leaves reveals UV-induced phytoalexin biosynthetic pathways and their regulatory networks in rice.
abstract: Rice produces diterpenoid and flavonoid phytoalexins for defense against pathogen attack. The production of phytoalexins in rice is also induced by UV-irradiation. To understand the metabolic networks involved in UV-induced phytoalexin biosynthesis and their regulation, phytochemical and transcriptomic analyses of UV-treated rice leaves were performed. In response to UV treatment, the accumulation of flavonoids was observed in rice leaves, which may serve as antioxidants against UV-induced oxidative stress. The phytochemical analysis confirmed sakuranetin accumulation and also demonstrated the induction of phenylamide synthesis in rice leaves by UV-irradiation. Transcriptomic analysis established that aromatic amino acid biosynthetic genes were immediately up-regulated after UV treatment. The genes involved in the phenylpropanoid pathway and flavonoid biosynthesis were also up-regulated. These findings suggest that the aromatic amino acid and flavonoid biosynthetic pathways are coordinately activated for the production of flavonoids and phenolic phytoalexins such as sakuranetin and phenylamides. An in silico analysis of UV-induced O-methyltransferase and acyltransferase genes suggested that these genes may be implicated in sakuranetin and phenylamide synthesis, respectively. The transcriptomic analysis also showed up-regulation of both methylerythritol phosphate pathway and the diterpenoid phytoalexin biosynthetic genes in response to UV treatment. A functional gene network analysis of phytoalexin biosynthetic and UV-induced genes for signaling components and transcription factors using RiceNet suggested that regulatory networks comprising signal perceiving receptor kinases, G-proteins, signal transducing mitogen-activated protein kinases and calcium signaling components, and transcription factors control flavonoid and phytoalexin biosynthesis in rice leaves under UV-C stress conditions.
authors.affiliation: Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Republic of Korea.
authors.forename: Hye Lin
authors.initials: HL
authors.lastname: Park
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Ki-Hong
authors.initials: KH
authors.lastname: Jung
authors.forename: Tae-Ryong
authors.initials: TR
authors.lastname: Hahn
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Cho
mesh_terms: D053898:Biosynthetic Pathways / Q000235:genetics; D003517:Cyclopentanes / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism; D008780:Methyltransferases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D054883:Oxylipins / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012717:Sesquiterpenes / Q000378:metabolism; D013729:Terpenes / Q000378:metabolism; D014466:Ultraviolet Rays; D015854:Up-Regulation / Q000187:drug effects; D000094162:Phytoalexins
chemical_list: D003517:Cyclopentanes; D005419:Flavonoids; D054883:Oxylipins; D010940:Plant Proteins; D012717:Sesquiterpenes; D013729:Terpenes; C099724:sakuranetin; D008780:Methyltransferases; D020928:Mitogen-Activated Protein Kinases; C041477:3-hydroxyflavone; D000094162:Phytoalexins
keywords: Diterpenoid phytoalexin; Gramineae; Oryza sativa L. spp. japonica cv. Dongjin; Phenylamide; Phytoalexin biosynthesis; Regulatory network; Rice; Rice transcriptome; Sakuranetin; UV-C radiation