title: Phenolic Phytoalexins in Rice: Biological Functions and Biosynthesis.
abstract: Phytoalexins are inducible secondary metabolites possessing antimicrobial activity against phytopathogens. Rice produces a wide array of phytoalexins in response to pathogen attacks and environmental stresses. With few exceptions, most phytoalexins identified in rice are diterpenoid compounds. Until very recently, flavonoid sakuranetin was the only known phenolic phytoalexin in rice. However, recent studies have shown that phenylamides are involved in defense against pathogen attacks in rice. Phenylamides are amine-conjugated phenolic acids that are induced by pathogen infections and abiotic stresses including ultra violet (UV) radiation in rice. Stress-induced phenylamides, such as N-trans-cinnamoyltryptamine, N-p-coumaroylserotonin and N-cinnamoyltyramine, have been reported to possess antimicrobial activities against rice bacterial and fungal pathogens, an indication of their direct inhibitory roles against invading pathogens. This finding suggests that phenylamides act as phytoalexins in rice and belong to phenolic phytoalexins along with sakuranetin. Phenylamides also have been implicated in cell wall reinforcement for disease resistance and allelopathy of rice. Synthesis of phenolic phytoalexins is stimulated by phytopathogen attacks and abiotic challenges including UV radiation. Accumulating evidence has demonstrated that biosynthetic pathways including the shikimate, phenylpropanoid and arylmonoamine pathways are coordinately activated for phenolic phytoalexin synthesis, and related genes are induced by biotic and abiotic stresses in rice.
authors.affiliation: Graduate School of Biotechnology, Kyung Hee University, Yongin 17104, Korea. manhocho@khu.ac.kr.
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Cho
authors.affiliation: Graduate School of Biotechnology, Kyung Hee University, Yongin 17104, Korea. swlee6803@khu.ac.kr.|Department of Plant Molecular Systems Biotechnology &amp; Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea. swlee6803@khu.ac.kr.
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
mesh_terms: D053898:Biosynthetic Pathways; D060467:Disease Resistance; D012275:Oryza / Q000737:chemistry / Q000502:physiology*; D010636:Phenols / Q000737:chemistry / Q000378:metabolism*; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism*; D013312:Stress, Physiological; D000094162:Phytoalexins
chemical_list: D010636:Phenols; D012717:Sesquiterpenes; D000094162:Phytoalexins
keywords: biotic/abiotic stress; phenolic phytoalexins; phenylamide; plant defense mechanism; rice; sakuranetin