Open AccessThe AVR4 effector is involved in cercosporin biosynthesis and likely affects the virulence of Cercospora cf. flagellaris on soybean
Author(s) -
Santos Rezende Josielle,
Zivanovic Marija,
Costa de Novaes Maria Izabel,
Chen ZhiYuan
Publication year - 2020
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1111/mpp.12879
Subject(s) - biology , mutant , cercospora , virulence , microbiology and biotechnology , effector , gene , chitinase , biochemistry , botany , leaf spot
Summary 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.