Botrytis cinerea Protein O-Mannosyltransferases Play Critical Roles in Morphogenesis, Growth, and Virulence

Mario González,Marcos Frías,Nélida Brito,Celedonio González

doi:10.1371/journal.pone.0065924

Mario González, Marcos Frías + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0065924

Copy DOI

Journal: PLoS ONE	Publication Date: Jun 6, 2013
Citations: 42	License type: CC BY 4.0

Affiliation: University of La Laguna

Abstract

Protein O-glycosylation is crucial in determining the structure and function of numerous secreted and membrane-bound proteins. In fungi, this process begins with the addition of a mannose residue by protein O-mannosyltransferases (PMTs) in the lumen side of the ER membrane. We have generated mutants of the three Botrytis cinerea pmt genes to study their role in the virulence of this wide-range plant pathogen. B. cinerea PMTs, especially PMT2, are critical for the stability of the cell wall and are necessary for sporulation and for the generation of the extracellular matrix. PMTs are also individually required for full virulence in a variety of hosts, with a special role in the penetration of intact plant leaves. The most significant case is that of grapevine leaves, whose penetration requires the three functional PMTs. Furthermore, PMT2 also contributes significantly to fungal adherence on grapevine and tobacco leaves. Analysis of extracellular and membrane proteins showed significant changes in the pattern of protein secretion and glycosylation by the pmt mutants, and allowed the identification of new protein substrates putatively glycosylated by specific PMTs. Since plants do no possess these enzymes, PMTs constitute a promising target in the development of novel control strategies against B. cinerea.

Highlights

Protein glycosylation is an important and highly conserved posttranslational modification consisting in the addition of carbohydrate residues to target proteins
In this work we have found that, to other filamentous fungi, the B. cinerea genome contains three pmt genes, coding for representatives of each of the three protein O-mannosyltransferases (PMTs) subfamilies
In the case of S. cerevisiae, regulation of pmt genes along the cell cycle has been reported, with maximal expression at the late G1 phase, and binding sites for the SBF transcription factor involved in activation of transcription at the late G1 phase were encountered in the promoters of most pmt genes [10]

Summary

Introduction

Protein glycosylation is an important and highly conserved posttranslational modification consisting in the addition of carbohydrate residues to target proteins It plays essential roles in eukaryotic cells from fungi to mammals [1], being crucial in determining the structure and function of numerous secreted and membrane-bound proteins. Mainly N-acetylglucosamine, N-acetylgalactosamine, mannose, galactose or glucose, can be linked to proteins via asparagine (N-glycosylation) or via hydroxylated amino acids including serine, threonine, and, more rarely, tyrosine, hydroxyproline and hydroxylysine (O-glycosylation). Both glycosylation pathways are conserved from prokaryotes to humans, but some differences exist in the class and number of the carbohydrate residues added [2,3]. There is no known consensus sequence for protein O-glycosylation sites, prediction tools have been developed for mammals [4] and it is generally accepted that the presence of regions rich in Ser/Thr residues in secretory proteins results in the addition of a high density of O-linked oligosaccharides [5,6,7]

Methods

Results

Conclusion