Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening
Lucille Alexander and Don Grierson1
Plant Science Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, UK
Received 11 April 2002; Accepted 2 July 2002
Elucidating the mechanisms involved in ripening of climacteric fruit and the role that ethylene plays in the process are key to understanding fruit production and quality. In this review, which is based largely on research in tomato, particular attention is paid to the role of specific isoforms of ACC synthase and ACC oxidase in controlling ethylene synthesis during the initiation and subsequent autocatalytic phase of ethylene production during ripening. Recent information on the structure and role of six different putative ethylene receptors in tomato is discussed, including evidence supporting the receptor inhibition model for ripening, possible differences in histidine kinase activity between receptors, and the importance of receptor LeETR4 in ripening. A number of ethyleneregulated ripening-related genes are discussed, including those involved in ethylene synthesis, fruit texture, and aroma volatile production, as well as experiments designed to elucidate the ethylene signalling pathway from receptor through intermediate components similar to those found in Arabidopsis, leading to transcription factors predicted to control the expression of ethylene-regulated genes. Key words: Carotenoid, climacteric, ethylene receptor, ethylene signal transduction, lipoxygenase, MAPKinase, tomato.
Abbreviations: ABA, abscisic acid; ACC, 1-aminocyclopropane-1-carboxylic acid; ACS, ACC synthase; ACO, ACC oxidase; PLP, pyridoxal-5'-phosphate; MAP3K, mitogen activated kinase kinase kinase; ERE, ethylene responsive element; PG, polygalacturonase, GUS, ß-glucuronidase; HPOs, unsaturated fatty acid hydroperoxides; LOX, lipoxygenase; ADH, alcohol dehyrogenase.
Journal of Experimental Botany, Vol. 53, No. 377,