Temporal expression of caffeic acid 3-O-methyltransferase (COMT) in mango (Mangifera indica var. Dashehari) fruit ripening

In the present study, evidence has been provided for the involvement of caffeic acid 3-O-methyltransferase (COMT) in mango fruit ripening at enzyme/protein and gene levels. A comt gene cloned from a cDNA library of ripe mango pulp exhibited 98% identity with the higher plant comt genes including substantial identity (81%) with flavonoid O-methyltransferase. Semi-quantitative RT-PCR experiments indicated that the comt transcript was present at low levels during the early stages of ripening but the relative expression augmented at ripened stage. Western blotting revealed a consistently coordinated increase in expression patterns of COMT protein in fully-ripe stage as compared to unripe stage. Use of the well established ripening delayer and an enhancer modulated COMT activity suggesting its role in mango ripening. The phenylpropanoid pathway has traditionally been associated with secondary metabolism and lignification, but, the present study suggests the involvement of comt in mango ripening and its possible role in flavonoid biosynthesis.