Characterization of a Tomato (Lycopersicon esculentum Mill.) Ripening-associated Membrane Protein (TRAMP) Gene Expression and Flavour Volatile Changes in TRAMP Transgenic Plants

The tomato ripening associated membrane protein (TRAMP) (Fray et al., 1994) is a member of the major intrinsic protein (MIP) family, defined as channels facilitating the passage of water and small solutes through membranes. During normal fruit ripening the TRAMP mRNA levels were increased whereas the expression levels of TRAMP in low ethylene ACO1-sense suppressed lines, Nr and rin fruits, were lower than at the breaker stage of wild type fruit. TRAMP mRNA is inhibited by $LaCl_3$, which is an inhibitor of $Ca^{2+}$-stimulated responses, treatment but drought condition did not affect TRAMP expression. The levels of TRAMP mRNA transcripts were substantially higher in the dark treated seedlings and fruits. These suggest that TRAMP function as a water channel may be doubted because of several reasons; no water content was changed during ripening in wild type, antisense and overexpression lines, TRAMP expression under light condition was lower than dark condition and TRAMP expression was not changed in drought condition. Co-suppression plant, 3588 was one of sense suppression lines, which contain CaMV 35S promoter and sense pNY507 cDNA, produced small antisense RNA, approximately 21-25 nucleotides in length, mediated post-transcriptional gene silencing. Therefore, TRAMP expression was inhibited by small antisense and multiple copies might induce gene silencing without any production of double strand RNA. Total seven selected volatile productions, isobutylthiazole, 6-methyl-5-hepten-2-one, hexanal, hexenal methylbutanal, hexenol, and methylbutanol, were highly reduced in sense line whereas total volatile production was increased in TRAMP antisense line. These results suggested TRAMP might change volatile related compounds.