Nuclear effectors in fungi: Many proteins essential for pathogenicity awaiting to be discovered

WALTER A. VARGAS; JOSÉ M. SANZ MARTÍN; GABRIEL E. RECH; MICHAEL R. THON; SERENELLA A. SUKNO

Conferencia; 12 th European Conference in Fungal Genetics; 2014

Through a comparative genomic analysis using seven pathogenic fungal species (Colletotrichum graminicola, Colletotrichum higginsianum, Magnaporthe oryzae, Ustilago maydis, Sporisorium reilianum, Cochliobolus heterostrophus and Fusarium graminearum), we uncovered 263 putative effector proteins likely to target the host nucleus as they simultaneously contain sequence signatures for secretion and nuclear localization. Using the pathosystem maize-Colletotrichum graminicola as a model system, we demonstrate that one of those putative proteins is a novel class of pathogenicity factor, CgEP1. This protein is synthesized during the early stages of disease development and is necessary for fungal hyphae to grow within the epidermal layer of the host. Genetic, molecular and biochemical studies confirmed that this novel effector targets the host nucleus, and is a novel class of DNA-binding protein with regulatory properties that is expressed during pathogenesis. From sequence analysis and allelic variation studies, we discovered that CgEP1 has undergone an intense evolution and selection process that led to duplications of complete internal repeats and has undergone episodes of positive selection. This effector family is also highly conserved in other monocot-infecting Colletotrichum species, affecting important crops such as sorghum, wheat and sugar cane. Our work functionally demonstrates the impact of effectoromics in the identification of novel/unknown effector protein in fungal species, and their potential use in the development of novel strategies for crop disease management.