生物
毒素
麦克赫里
突变体
微生物学
荧光假单胞菌
调节器
抑制因子
细胞生物学
斜纹夜蛾
基因
基因表达
细菌
绿色荧光蛋白
遗传学
植物
有害生物分析
夜蛾科
作者
Maria Péchy‐Tarr,Naomi Borel,Peter Kupferschmied,Vincent Turner,Olivier Binggeli,Dragica Radovanovic,M. Maurhofer,Christoph Keel
标识
DOI:10.1111/1462-2920.12050
摘要
Summary P seudomonas fluorescens CHA 0 is a root‐associated biocontrol agent that suppresses soil‐borne fungal diseases of crops. Remarkably, the pseudomonad is also endowed with systemic and oral activity against pest insects which depends on the production of the insecticidal Fit toxin. The toxin gene ( fitD ) is part of a virulence cassette encoding three regulators ( FitF , FitG , FitH ) and a type I secretion system ( FitABC‐E ). Immunoassays with a toxin‐specific antibody and transcriptional analyses involving fitG and fitH deletion and overexpression mutants identified LysR family regulator FitG and response regulator FitH as activator and repressor, respectively, of Fit toxin and transporter expression. To visualize and quantify toxin expression in single live cells by fluorescence microscopy, we developed reporters which in lieu of the native toxin protein express a fusion of the Fit toxin with red fluorescent mCherry . In a wild‐type background, expression of the mCherry ‐tagged Fit toxin was activated at high levels in insect hosts, i.e. when needed, yet not on plant roots or in batch culture. By contrast, a derepressed fitH mutant expressed the toxin in all conditions. P . fluorescens hence can actively induce insect toxin production in response to the host environment, and FitH and FitG are key regulators in this mechanism.
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