One of the most devastating fungal diseases of soybean in the southern USA is Cercospora leaf blight (CLB), which is caused mainly by Cercospora cf. flagellaris. Recent studies found that the fungal effector AVR4, originally identified in Cladosporium fulvum as a chitin‐binding protein, is highly conserved among other Cercospora species. We wanted to determine whether it is present in C. cf. flagellaris and, if so, whether it plays a role in the pathogen infection of soybean. We cloned the Avr4 gene and created C. cf. flagellaris ∆avr4 mutants, which produced little cercosporin and significantly reduced expression of cercosporin biosynthesis genes. The ∆avr4 mutants were also more sensitive to chitinase and showed reduced virulence on soybean compared to the wild‐type. The observed reduced virulence of C. cf. flagellaris ∆avr4 mutants on detached soybean leaves is likely due to reduced cercosporin biosynthesis. The phenotypes of reduced cercosporin production and cercosporin pathway gene expression, similar to those of the ∆avr4 mutants, were reproduced when wild‐type C. cf. flagellaris was treated with double‐stranded RNA targeting Avr4 in vitro. These two independent approaches demonstrated for the first time the direct involvement of AVR4 in the biosynthesis of cercosporin.

中文翻译：

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AVR4效应子参与头孢菌素的生物合成，并可能影响头孢菌素的毒力。在大豆上的鞭毛。

Cercospora叶枯病（CLB）是美国南部最具破坏力的大豆真菌病之一，主要由Cercospora cf引起。鞭毛虫。最近的研究发现，真菌效应子AVR4最初在苜蓿叶形梭菌（Cladosporium fulvum）中被鉴定为几丁质结合蛋白，在其他Cercospora物种中高度保守。我们想确定它是否存在于C. cf. 鞭毛以及是否在大豆病原体感染中起作用。我们克隆了Avr4基因并创建了C. cf. flagellaris Δ avr4突变体，其几乎不产生头孢菌素并显着降低了头孢菌素生物合成基因的表达。该Δ avr4突变体也以几丁质酶更敏感，相比于野生型显示出降低的对大豆的毒力。所观察到的毒力降低C.比照 flagellaris Δ avr4对大豆离突变可能是由于减少cercosporin生物合成。的减少cercosporin生产和cercosporin途径基因表达表型，类似于Δ的avr4突变体，进行再现时的野生型C.比照 在体外用靶向Avr4的双链RNA处理鞭毛 。这两种独立的方法首次证明了AVR4直接参与头孢菌素的生物合成。