Regulation of ethylene biosynthesis in response to pollination in tomato flowers

Pollination of many flowers leads to an increase in ethylene synthesis and flower senescence. We have investigated the regulation of pollination-induc ed ethylene synthesis in tomato (Lycopersicon esculentum) using flowers of the dialytic (dl) mutant, in which pollination can be manipulated experimen tally, with the aim of developing a model system to study tomato flower sen escence. Ethylene synthesis increased rapidly in dl pistils following polli nation, leading to accelerated petal senescence, and was delayed in ethylen e-insensitive Never ripe (Nu) pistils. However, NY pistils eventually produ ced more ethylene than dl pistils, suggesting the presence of negative feed back regulation of ethylene synthesis following pollination. LEACS1A expres sion correlated well with increased ethylene production in pollinated dl pi stils, and expression in Nr revealed that regulation is via an ethylene-ind ependent mechanism. In contrast, the induction of the 1-aminocyclopropane-1 -carboxylic acid oxidases, LEACO1 and LEACO3, following pollination is ethy lene dependent. In addition, the expression profiles of ACS and ACO genes w ere determined during petal senescence and a hypothesis proposed that trans located 1-aminocyclopropane-1-carboxylic acid from the pistil may be import ant for regulating the initial burst of ethylene production during petal se nescence, These results are discussed and differences between tomato and th e ornamental species previously studied are highlighted.