Abstract
The genus Colletotrichum contains a large number of phytopathogenic fungi that produce enormous economic losses around the world. The effect of horizontal gene transfer (HGT) has not been studied yet in these organisms. Inter-Kingdom HGT into fungal genomes has been reported in the past but knowledge about the HGT between plants and fungi is particularly limited. We describe a gene in the genome of several species of the genus Colletotrichum with a strong resemblance to subtilisins typically found in plant genomes. Subtilisins are an important group of serine proteases, widely distributed in all of the kingdoms of life. Our hypothesis is that the gene was acquired by Colletotrichum spp. through (HGT) from plants to a Colletotrichum ancestor. We provide evidence to support this hypothesis in the form of phylogenetic analyses as well as a characterization of the similarity of the subtilisin at the primary, secondary and tertiary structural levels. The remarkable level of structural conservation of Colletotrichum plant-like subtilisin (CPLS) with plant subtilisins and the differences with the rest of Colletotrichum subtilisins suggests the possibility of molecular mimicry. Our phylogenetic analysis indicates that the HGT event would have occurred approximately 150–155 million years ago, after the divergence of the Colletotrichum lineage from other fungi. Gene expression analysis shows that the gene is modulated during the infection of maize by C. graminicola suggesting that it has a role in plant disease. Furthermore, the upregulation of the CPLS coincides with the downregulation of several plant genes encoding subtilisins. Based on the known roles of subtilisins in plant pathogenic fungi and the gene expression pattern that we observed, we postulate that the CPLSs have an important role in plant infection.
Highlights
The genus Colletotrichum within the Ascomycetes includes a large number of phytopathogenic species that affect a wide range of crops worldwide [1,2]
The proteins GLRG_05578 and CGLO_07890 were identified as members of the subtilisin S8A family and they were designated as Colletotrichum plant-like subtilisins (CPLSs)
Phylogenetic analysis, domain content and tertiary structure prediction allowed us to identify the presence of a plant-like member of the subtilisin S8A family in the genome of Colletotrichum graminicola and Colletotrichum gloeosporioides
Summary
The genus Colletotrichum within the Ascomycetes includes a large number of phytopathogenic species that affect a wide range of crops worldwide [1,2]. Species of this genus are the agents of anthracnose diseases that cause devastating yield losses in agriculture [3]. One of the largest groups of catalytic enzymes is composed of serine proteases, a group of proteins that can be found in all kingdoms of life [7,8] These enzymes include endopeptidases and exopeptidases organized into 12 clans and 35 families according to the MEROPS peptidase database [9].
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