Control of ripening in transgenic tomatoes

Abstract

Major progress has been made over the last few years in the identification and regulation of tomato ripening genes . At least 25 genes showing elevated expression during ripening have been cloned and several, including polygalacturonase, which modifies fruit textures, have been shown to be ripening-specific . In addition, genes have been cloned for ACC synthase and ACC oxidase, which control the synthesis of ethylene, which plays a critical role in ripening . Inhibition of expression of polygalacturonase, pectinesterase, ACC synthase, ACC oxidase and phytoene synthase has been achieved in transgenic plants, using antisense technology. The expression of several genes has also been inhibited by sense gene suppression . New traits caused by these transgenes are stably inherited . Antisense tomatoes with reduced polygalacturonase have improved textural qualities which are being exploited commercially for the fresh and processed markets . Overexpression of phytoene synthase has been shown to restore carotenoid production in the yellow flesh mutant and can be used to enhance colour in other cultivars . Antisense fruit in which ACC synthase or ACC oxidase are inhibited show slower ripening and reduced over-ripening . ACC oxidase antisense genes have also been shown to delay leaf senescence . It is to be expected that further genes determining other quality traits will be identified and manipulated soon .

Assessment of representational difference analysis (RDA) to construct informative cDNA microarrays for gene expression analysis of species with limited transcriptome information, using red and green tomatoes as a model

“…From this, it can be concluded that the procedure effectively selects for sequences that are uniquely present in green or red tomatoes, or that the two physiological conditions have very little in common. The latter may be true, since the green/breaker stages are reported to be the physiologically most active stages of ripening (Moore et al, 2002) with declining and markedly changed physiological activity towards the more mature, red stages (Fraser et al, 1995;Kende, 1989;Grierson and and Fray, 1994;Giovannoni et al, 1989). Recent literature suggests (LemaireChamley et al, 2005) it is likely that the physiological activity in the developing green fruit is even higher, but this is outside the scope of the experiments discussed here.…”

A Novel Small Heat Shock Protein Gene,vis1, Contributes to Pectin Depolymerization and Juice Viscosity in Tomato Fruit

“…vis1 is regulated by fruit ripening and high temperature and exhibits a typical heat shock protein chaperone function when expressed in bacterial cells. We propose that VIS1 contributes to physiochemical properties of juice, including pectin depolymerization, by reducing thermal denaturation of depolymerizing enzymes during daytime elevated temperatures.Ripening of fleshy fruits is a dynamic transitional period that encompasses a myriad of biochemical and physiological changes leading to easily perceivable alterations in fruit texture, firmness, pigmentation, aroma, and sweetness (Tucker, 1993;Grierson and Fray, 1994). Significant progress has been made in characterizing the molecular components of fruitripening process, including ethylene biosynthesis and perception, cell wall depolymerization, light signal transduction, and carotenoid accumulation (Giovannoni, 2001).…”

“…Ripening of fleshy fruits is a dynamic transitional period that encompasses a myriad of biochemical and physiological changes leading to easily perceivable alterations in fruit texture, firmness, pigmentation, aroma, and sweetness (Tucker, 1993;Grierson and Fray, 1994). Significant progress has been made in characterizing the molecular components of fruitripening process, including ethylene biosynthesis and perception, cell wall depolymerization, light signal transduction, and carotenoid accumulation (Giovannoni, 2001).…”

Overview: The Many Uses and Applications of Transgenic Plants

“…Several types of transgenic tomato have been produced commercially (see KRIDI. and SHEWMAKER 1996;KRAMER and REDENBAUGH 1994;GRIERSON and FRAY 1994). Another approach to improved flavor is the expression of the sweet protein monellin in both tomato and lettuce (PENARRUBIA et al 1992).…”