Evaluation of Plant and Fungi Thaumatin-like Genes during Witches' Broom Disease of Cacao

Theobroma cacao has economic relevance offering the main raw material for chocolate production: the commodity cocoa beans. In Brazil, the Bahia state was ranked the second among world's largest producers. Recently that region had the production devastated by witches broom disease, a serious illness caused by Moniliophora perniciosa. After this occurrence the region rank now the fifth on global production, turning Brazil to an importer country. In this context, Witche’s broom genome initiative and several projects are aiming to find a solution for this disease. A search in the genome and RNA-seq libraries resulted in the identification of Thaumatin- like genes expressed by fungus and plants. Thaumatins are expressed during hypersensitive response (HR) in plant-pathogen interactions, being classified as PR-5 (pathogenicity related protein class-5). Thaumatins have antifungal and ß-glucanolitic activities. Recently a new wheat thaumatin-like protein was described as a xylanase inhibitor. In Moniliophtora perniciosa, thaumatin-like protein's roles are still unclear. Gene expression analyses of thaumatin-like genes from Theobroma cacao and M. perniciosa have shown a diverse pattern of expression demonstrating a different correlation with the fungi infection. Preliminary results indicate divergent functions among gene family members. Further investigation is currently in place to clarify the biological significance of the differentially expressed genes in both plant and fungi during the disease development.