Regulation of Gene Expression by Ethylene in Wild-Type and rin Tomato (Lycopersicon esculentum) Fruit.

Levels of ethylene biosynthesis and ethylene-inducible gene expression in wild-type tomato (Lycopersicon esculentum) fruit and in nonripening fruit from the tomato mutant rin (ripening inhibitor) were compared in order to investigate the mechanism of ethylene action. Whereas wild-type tomato fruit dramatically increase the rate of ethylene biosynthesis at the onset of ripening, rin fruit constitutively produce ethylene at a low basal level. We have compared the mRNA levels and transcription rates of four cloned ethylene-inducible genes (JE Lincoln, S Cordes, E Read, RL Fischer 1987 Proc Natl Acad Sci USA 84: 2793-2797) during wild-type and rin fruit development. In wild-type fruit, both mRNA levels and transcription rates of these genes increase. The effect of the rin mutation on gene expression is different for each ethylene-inducible gene. In one case expression is completely suppressed, while in other instances it is either partially inhibited or relatively unaffected by the mutation. The mRNA levels of each of these genes in response to exogenous ethylene in rin fruit was also measured. The mRNAs for all four genes accumulate to similar levels in both ethylene treated rin and ethylene treated wild-type fruit. These results are discussed with regard to the response of plants to ethylene hormone at the level of gene expression.