DisplayTitle

Differential Gene Expression Between the Biotrophic-Like and Saprotrophic Mycelia of the Witches' Broom Pathogen Moniliophthora perniciosa

¹Laboratório de Genômica e Expressão, Departamento de Genética e Evolução, Instituto de Biologia, Universidade Estadual de Campinas, CP 6109, Campinas 13083-970, São Paulo, Brazil; ²Laboratório de Genômica e Biologia Molecular, Centro de Pesquisa Hospital A. C. Camargo, Rua Prof. Antonio Prudente 109, 1° andar, São Paulo city 01509-010, São Paulo, Brazil; ³Laboratório de Virologia e Bacteriologia de Plantas, Instituto Agronômico do Parana—IAPAR, Londrina 86047-902, Paraná, Brazil; ⁴Laboratório de Genômica e Expressão Gênica, Departamento de Genética e Biologia Molecular, Universidade Estadual de Santa Cruz, Ilhéus 45650-000, Bahia, Brazil; ⁵Laboratório de Bioquímica de Plantas, Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba 13400-970, São Paulo, Brazil; ⁶Sustainable Perennial Crops Laboratory, United States Department of Agriculture--Agricultural Research Service, 10300 Baltimore Ave., Bldg. 001, Beltsville, MD 20705-2350, U.S.A.

Moniliophthora perniciosa is a hemibiotrophic fungus that causes witches' broom disease (WBD) in cacao. Marked dimorphism characterizes this fungus, showing a monokaryotic or biotrophic phase that causes disease symptoms and a later dikaryotic or saprotrophic phase. A combined strategy of DNA microarray, expressed sequence tag, and real-time reverse-transcriptase polymerase chain reaction analyses was employed to analyze differences between these two fungal stages in vitro. In all, 1,131 putative genes were hybridized with cDNA from different phases, resulting in 189 differentially expressed genes, and 4,595 reads were clusterized, producing 1,534 unigenes. The analysis of these genes, which represent approximately 21% of the total genes, indicates that the biotrophic-like phase undergoes carbon and nitrogen catabolite repression that correlates to the expression of phytopathogenicity genes. Moreover, downregulation of mitochondrial oxidative phosphorylation and the presence of a putative ngr1 of Saccharomyces cerevisiae could help explain its lower growth rate. In contrast, the saprotrophic mycelium expresses genes related to the metabolism of hexoses, ammonia, and oxidative phosphorylation, which could explain its faster growth. Antifungal toxins were upregulated and could prevent the colonization by competing fungi. This work significantly contributes to our understanding of the molecular mechanisms of WBD and, to our knowledge, is the first to analyze differential gene expression of the different phases of a hemibiotrophic fungus.

Additional keywords:DNA microarrays.