Genome-wide in silico identification of GPI proteins in Mycosphaerella fijiensis and transcriptional analysis of two GPI-anchored β-1,3-glucanosyltransferases

Abstract

The hemibiotrophic fungus Mycosphaerella fijiensis is the causal agent of black Sigatoka (BS), the most devastating foliar disease in banana (Musa spp.) worldwide. Little is known about genes that are important during M. fijiensis-Musa sp. interaction. The fungal cell wall is an attractive area of study because it is essential for maintenance of cellular homeostasis and it is the most external structure in the fungal cell and therefore mediates the interaction of the pathogen with the host. In this manuscript we describe the in silico identification of glycosyl phosphatidylinositol-protein (GPI) family in M. fijiensis, and the analysis of two β-1,3-glucanosyltrans-ferases (Gas), selected by homology with fungal pathogenicity factors. Potential roles in pathogenesis were evaluated through analyzing expression during different stages of black Sigatoka disease, comparing expression data with BS symptoms and fungal biomass inside leaves. Real-time quantitative RT-PCR showed nearly constant expression of MfGAS1 with slightly increases (about threefold) in conidia and at speck-necrotrophic stage during banana-pathogen interaction. Conversely, MfGAS2 expression was increased during biotrophy (about seven times) and reached a maximum at speck (about 23 times) followed by a progressive decrease in next stages, suggesting an active role in M. fijiensis pathogenesis.

• black Sigatoka disease
• cell wall
• fungal pathogenesis
• gene expression

Acknowledgments

The authors thank the Genome Portal of the Department of Energy Joint Genome Institute, Dr Gert Kema and Dr Stephen B. Goodwin for the facilities provided to gain access to the sequence of the M. fijiensis genome, Consejo Nacional de Ciencia y Tecnología (CONACyT, México) for the financial support to Basic Science project No. 54864-Z and for doctoral scholarship 169615 to N. Kantún-Moreno. We thank FORDECyT contract 116886 for supplemental financial support for qRT-PCR analysis and Dr José Ruiz Herrera for critical review of the manuscript.