Systematic Identification And Functional Analysis Of CFEM Effectors In Colletotrichum Graminicola

Maize is one of the most important food and economic crops. Its production and quality affect the quality of human life in the world. Maize anthracnose is caused by the fungal pathogen Colletotrichum graminicola that produces oval to spindle shaped brown spots on leaves. The disease hinders plant photosynthesis, reduces yield and causes economic losses. Previous research shows that CFEM（common in several fungal extracellular membrane protein） effectors play important roles in pathogen infection and signal pathway. In this study, we performed a systematic identification and functional analysis of the CFEM effector repertoires encoded in the C. graminicola genome so that we can better understand C. graminicola pathogenesis and develop new control methods for maize anthracnose.Systematic bioinformatic analysis of the CFEM effectors in C. graminicola led to the identification of 22 CFEM candidate effectors that were selected for functional analysis. First, we performed transcriptional analysis of the candidate effector genes and cloned the full-length（FL） and cDNAs without the signal peptide（NS） into an expression vector. Second, we performed subcellular localization and cell death induction or suppression screens with the pGDR transient expression vector in Nicotiana benthamiana. Finally, we knocked out the candidate effectors which can suppress cell death induced by Bax and has the nucleus or whole cell localization. In addition, we analyzed the pathogenesis of the knock-out mutants on maize plants. Our results demonstrate that the CFEM candidate effectors show various transcription expression patterns, 7 candidate effectors have nucleus localization, 7 candidate effectors can suppress cell death induced by Bax and the GLRG₀1006.1 KO mutant grows slowly and its pathogenesis is reduced compared to the wild type. Our results demonstrate that C. graminicola can suppress the maize immune system effectively by delivering various effectors with different transcriptional patterns and localizations to cause disease.