摘要
黄单胞菌属病原菌能侵染约400种植物,造成严重的经济损失。黄单胞菌的一个重要特征是产生具有保护功能的菌黄素。菌黄素是一类含有两个溴修饰的芳香多烯类磷脂化合物,但负责溴修饰的基因及其溴化机理还不清楚。本研究以野油菜黄单胞菌XC1菌株和稻黄单胞菌PXO99A菌株菌黄素生物合成基因簇中的xanJ为研究对象,开展了生物信息学、遗传学、生物化学和病理学等方面的探究,初步阐明了xanJ的生物学功能。XanJ含有一个FAD结合结构域或一个色氨酸卤化酶结构域,拥有高度保守基序GXGXXG和WXWXIP,属于一类FAD依赖型卤化酶;xanJ敲除突变体无法合成双溴菌黄素,但仍能合成少量无溴化修饰的菌黄素;xanJ突变体中菌黄素前体3-羟基苯甲酸和4-羟基苯甲酸无积累;在xanJ突变体中过表达已知的酚类卤化酶基因ab10、bmp5、aerJ和mcnD无法恢复双溴菌黄素的生物合成;敲除xanJ不影响病原菌的胞外纤维素酶﹑胞外蛋白酶和胞外多糖的生物合成,也不影响对甘蓝的致病性。因此,XanJ可能负责菌黄素多烯链上β-碳原子的溴化,并参与菌黄素生物合成过程中的多烯链延伸。
The phytopathogenic Xanthomonas can infect approximately 400 plant species,causing serious economic losses in agriculture.One of the most important characteristics of Xanthomonads is to produce xanthomonadin,a kind of protective yellow pigment.Xanthomonadins are phospholipids with di-brominated aryl-polyene,however,mechanisms underlying xanthomonadin bromination remain unclear.In this study,the function of xanJ,one of the key genes required for xanthomonadin biosynthesis in Xanthomoas campestris pv.campestris strain XC1 and Xanthomoas oryzae pv.oryzae strain PXO99A,was investigated using bioinformatics,genetic,biochemical and pathological methods.XanJ protein contains a flavin adenine dinucleotide(FAD)-binding domain and a tryptophan halogenase domain,and harbors GXGXXG and WXWXIP motifs,suggesting that this protein is a FAD-dependent phenolic halogenase.Deletion of xanJ abolished the biosynthesis of dibrominated aryl-polyene.However,the xanJ deletion mutant strain still produces low levels of non-brominated xanthomonadin.No accumulation of 3-hydroxybenzoic acid and 4-hydroxybenzoic acid,the precursors of xanthomonadin biosynthesis,was observed in the xanJ deletion mutant strains.Overexpression of the phenolic halogenases encoding genes ab10,bmp5,aerJ or mcnD,which encoding phenolic halogenases,in the xanJ deletion mutant strains failed to restore the biosynthesis of di-brominated xanthomonadin.Additionally,deletion of xanJ had no effects on exopolysaccharide biosynthesis,extracellular endoglucanase,protease activities and virulence on cabbage.These findings indicate that XanJ is a FAD-dependent brominase most likely involved in bromination ofß-carbon of aryl-polyene and the elongation of polyene chain in xanthomonadin biosynthesis.
作者
郑哲麟
曹雪强
胡文达
宋凯
郝祥蕊
张红艳
何亚文
ZHENG Zhelin;CAO Xueqiang;HU Wenda;SONG Kai;HAO Xiangrui;ZHANG Hongyan;HE Yawen(State Key Laboratory of Microbial Metabolism,Joint International Research Laboratory of Metabolic&Development Sciences,SJTU-NLBP Joint R&D Center on Biopesticides and Biofertilizers,School of Life Sciences&Biotechnology,Shanghai Jiao Tong University(SJTU),Shanghai 200240,China;College of Biotechnology and Bioengineering,Zhe Jiang University of Technology,Hangzhou 310014,China;Shanghai Nong Le Biological Products Company Limited(NLBP),Shanghai 201419,China)
出处
《植物病理学报》
CAS
CSCD
北大核心
2023年第2期229-244,共16页
Acta Phytopathologica Sinica
基金
国家自然科学基金(31972231、32172355)。
