CgNPG1 as a Novel Pathogenic Gene of Colletotrichum gloeosporioides From Hevea brasiliensis in Mycelial Growth, Conidiation, and the Invasive Structures Development.

Chen Liang,Yun Zhou,Hongyan Yin,Chaozu He,Hongli Luo,Bang An,Daozhe Lin,Bei Zhang

doi:10.3389/fmicb.2021.629387

Abstract

The rubber tree (Hevea brasiliensis) is a tropical perennial crop for the primary source of natural rubber. Colletotrichum gloeosporioides from Hevea brasiliensis (C. gloeosporioides Hb) and Colletotrichum acutatum from Hevea brasiliensis (C. acutatum Hb) are the causal agents of rubber tree anthracnose and lead to serious loss of natural rubber production. Inoculation tests showed that C. gloeosporioides Hb possessed higher pathogenicity than C. acutatum Hb to the rubber tree. Genomic analysis revealed that an unknown gene, named CgNPG1 (a Novel Pathogenic Gene 1), was presented in the genome of C. gloeosporioides Hb but not identified in C. acutatum Hb. CgNPG1 was predicted to encode a small secretory protein without any conserved domain. To investigate the functions of CgNPG1 in C. gloeosporioides Hb and in C. acutatum Hb, the gene deletion and overexpression mutants were generated. The phenotype analysis showed that deletion of CgNPG1 led to changed conidia morphology, decreased mycelial growth, conidiation, conidia germination rate, appressorium formation rate, and pathogenicity of C. gloeosporioides Hb to the rubber tree. Meanwhile, heterogeneous expression of CgNPG1 in C. acutatum Hb significantly changed the conidia morphology and improved the mycelial growth rate, conidiation, conidia germination rate, appressorium formation rate, and the pathogenicity of C. acutatum Hb to the rubber tree. Consistently, CgNPG1 increased the expression level of CaCRZ1 and CaCMK1 in C. acutatum Hb. These data suggested that CgNPG1 contributed to mycelial growth, conidiation, the development of invasive structures, and the pathogenicity of Colletotrichum to the rubber tree, which might be related to the modulation of CaCRZ1 and mitogen-activated protein kinase CMK1. Our results provided new insight into CgNPG1 in regulating growth and pathogenicity of the Colletotrichum spp.

Highlights

Colletotrichum as asexual genus is classified into fungi imperfecti, coelomycetes (Dean et al, 2012)
Colletotrichum gloeosporioides from Hevea brasiliensis and Colletotrichum acutatum from Hevea brasiliensis strains were isolated from the leaves of Hevea brasiliensis with anthracnose in Hainan province
Colletotrichum gloeosporioides from Hevea brasiliensis and Colletotrichum acutatum from Hevea brasiliensis were isolated and characterized from rubber trees in Hainan province of China

Summary

Introduction

Colletotrichum as asexual genus is classified into fungi imperfecti, coelomycetes (Dean et al, 2012). Most Colletotrichum species feed on hemibiotrophy, exhibiting initially a brief biotrophic phase with large intracellular primary hyphae and later a destructive, necrotrophic phase with narrower secondary hyphae, which ramify throughout the host tissue (Münch et al, 2008; Dean et al, 2012). Among these Colletotrichum species, Colletotrichum acutatum, and Colletotrichum gloeosporioides are frequently mentioned and reported because of early taxonomic confusion (Dean et al, 2012). Several reports have revealed that horizontal gene transfer (HGT) and horizontal chromosome transfer (HCT) between plant pathogenic fungi affect their host range and virulence (Mehrabi et al, 2011; Jaramillo et al, 2014)

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