Cho Man-Ho, Lee Sang-Won
Graduate School of Biotechnology, Kyung Hee University, Yongin 17104, Korea.
Department of Plant Molecular Systems Biotechnology & Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea.
Int J Mol Sci. 2015 Dec 7;16(12):29120-33. doi: 10.3390/ijms161226152.
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.
植保素是可诱导产生的次生代谢产物，对植物病原体具有抗菌活性。水稻在受到病原体攻击和环境胁迫时会产生多种植保素。除少数例外，在水稻中鉴定出的大多数植保素都是二萜类化合物。直到最近，黄酮类化合物樱花素还是水稻中唯一已知的酚类植保素。然而，最近的研究表明，苯酰胺参与了水稻对病原体攻击的防御。苯酰胺是胺共轭酚酸，在水稻中由病原体感染和包括紫外线（UV）辐射在内的非生物胁迫诱导产生。据报道，胁迫诱导的苯酰胺，如N-反式肉桂酰色胺、N-对香豆酰血清素和N-肉桂酰酪胺，对水稻细菌和真菌病原体具有抗菌活性，这表明它们对入侵病原体具有直接抑制作用。这一发现表明，苯酰胺在水稻中作为植保素起作用，并且与樱花素一起属于酚类植保素。苯酰胺还与水稻抗病性的细胞壁强化和化感作用有关。酚类植保素的合成受到植物病原体攻击和包括紫外线辐射在内的非生物挑战的刺激。越来越多的证据表明，包括莽草酸途径、苯丙烷途径和芳基单胺途径在内的生物合成途径在酚类植保素合成中被协同激活，并且相关基因在水稻中受到生物和非生物胁迫的诱导。
