CICY Merida. MŽxico.
Muhilan Mahendhiran , Miguel Tzec, Blondy Canto Canche, Rosa Grijalva Arango, Jorge Ramirez Prado and Andrew James
Biotechnology Unit, Centro de Investigacion Cientifica de Yucatan, Merida, Yucatan, Mexico
RESUMEN (ABSTRACT)
Differences in the physico-chemical properties and content of starch, total sugars and reducing sugars in ripe and unripe fruits of Musa cultivars distinguish between dessert, plantain (AAB genome), cooking (ABB) and beer bananas (AAA). These properties also are the basis for differences in economically important post harvest characteristics. Many of the enzymes involved in starch metabolism occur in multiple isoforms which differentialy affect glucan chain length, degree of amylopectin branching and molecular size. In summary, the granular structure of starch is determined by the properties of the synthesizing enzymes present at the site of glucan branch formation. As a first step to a molecular understanding, and for the development of molecular COS markers for differences in these traits, we have selected 7 candidate genes (AGPase, starch synthase, sucrose synthase, starch branching, starch debranching, pullulinase and isoamylase) for sequencing and bioinformatic analysis. Without a complete banana genome sequence we have found problems in amplifying fragments of these genes due to the large size, unknown location and frequency of introns. However, to date, we have sequenced, in a range of banana wild species and cultivars, conserved fragments of the genes for AGPase, starch synthase and sucrose synthase; key metabolic steps in starch anabolism and catabolism. After bioinformatic analysis we have discovered polymorphisms in these genes which are associated with the different properties of Musa fruit such as are found in dessert bananas, plantains, cooking and beer-making bananas.