tailieunhanh - Báo cáo Y học: Molecular and biochemical characteristics of a gene encoding an alcohol acyl-transferase involved in the generation of aroma volatile esters during melon ripening

Two genes (CM-AAT1 and CM-AAT2) with strong sequence homology (87% identity at the protein level) putatively involved in the formation of aroma volatile esters have been isolated from Charentais melon fruit. They belong to a large and highly divergent family of multifunctional plant acyl-transferases and show at most 21% identity to the only other fruit acyl-transferase characterized so far in strawberry. RT-PCR studies indicated that both genes were specifically expressed in fruit at increasing rates in the early and mid phases of ripening. Expression was severely reduced in ethylene-suppressed antisense ACC oxidase (AS) fruit and in wild-type (WT) fruit treated. | Eur. J. Biochem. 269 2359-2366 2002 FEBS 2002 doi Molecular and biochemical characteristics of a gene encoding an alcohol acyl-transferase involved in the generation of aroma volatile esters during melon ripening Fikri E. L. Yahyaoui1 Chalermchai Wongs-Aree2 Alain Latche1 Rachel Hackett2 Don Grierson2 and Jean-Claude Pech1 1UMR990 -INPỊENSAT-INRA Castanet-Tolosan France 2Plant Science Division School of Biocciences The University of Nottingham UK Two genes CM-AAT1 and CM-AAT2 with strong sequence homology 87 identity at the protein level putatively involved in the formation of aroma volatile esters have been isolated from Charentais melon fruit. They belong to a large and highly divergent family of multifunctional plant acyl-transferases and show at most 21 identity to the only other fruit acyl-transferase characterized so far in strawberry. RT-PCR ttudies indicated that both genes were specifically expressed in fruit at increasing rates in the early and mid phases of ripening. Exptession was severely reduced in ethylene-suppressed antisense ACC oxidase AS fruit and in wild-type WT fruit treated with the ethylene antagonist 1-MCP. Cloníng of the wo g r s in yeast revealed that the CM-AAT1 protein exhibited alcohol acyl-transferase activity while no such activity could be detected for CM-AAT2 despite the strong homology between the two sequences. CM-AAT1 was eaaal kt of producing esters from a wide range of combinations of alcohols and acyl-CoAs. Tlte 111 1 1 die aaAm dam of aliphatic alcohols the higher the activity. Branched accohols were esterified at differential rates depending on the position of the methyl group and the nature of the acyl donor. Phenyl and benzoyl alcohols were also good substrates but activity varied with the position and size of the aromatic residue. The cis trans configuration influenced activity either positively 2-hexenol or negatively 3-hexenol . hecuute ripening melons evolve the whole range of esters .