Cacao molecular biology research at Penn State University is directed at six areas: 1) regenerating trees from tissue culture, 2) genetically transforming the tree, 3) cloning lipid biosynthetic genes, 4) characterizing the genomes, 5) isolating genes that may confer fungal disease resistance, and 6) creating an RFLP linkage map. An accomplishment with tissue culture studies is developing a method to readily induce "break" in excised lateral buds. These results will lead to the rapid propagation of selected cultivars. Because a long-term goal is to engineer the tree for a hard cocoa butter regardless of the climate, we have cloned a putative glycerol-3-phosphate acyltransferase gene, the first one in the cocoa butter biosynthetic pathway. Another project is to eventually engineer cacao to be more resistant to fungal diseases; thus cocoa genomic library is being screened for the gene encoding beta-1,3-glucanase, a hydrolase which degrades fungal cell walls. To more thoroughly understand the molecular biology of cacao, the nuclear genome is being characterized. Preliminary evidence suggests the cacao nuclear genome is smaller than that of most higher plants. Finally, efforts have begun to genetically transform the tree, and to develop a map of the cacao genome based on RFLPs.


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