title: Fruit-localized phytochromes regulate lycopene accumulation independently of ethylene production in tomato.
abstract: We show that phytochromes modulate differentially various facets of light-induced ripening of tomato fruit (Solanum lycopersicum L.). Northern analysis demonstrated that phytochrome A mRNA in fruit accumulates 11.4-fold during ripening. Spectroradiometric measurement of pericarp tissues revealed that the red to far-red ratio increases 4-fold in pericarp tissues during ripening from the immature-green to the red-ripe stage. Brief red-light treatment of harvested mature-green fruit stimulated lycopene accumulation 2. 3-fold during fruit development. This red-light-induced lycopene accumulation was reversed by subsequent treatment with far-red light, establishing that light-induced accumulation of lycopene in tomato is regulated by fruit-localized phytochromes. Red-light and red-light/far-red-light treatments during ripening did not influence ethylene production, indicating that the biosynthesis of this ripening hormone in these tissues is not regulated by fruit-localized phytochromes. Compression analysis of fruit treated with red light or red/far-red light indicated that phytochromes do not regulate the rate or extent of pericarp softening during ripening. Moreover, treatments with red or red/far-red light did not alter the concentrations of citrate, malate, fructose, glucose, or sucrose in fruit. These results are consistent with two conclusions: (a) fruit-localized phytochromes regulate light-induced lycopene accumulation independently of ethylene biosynthesis; and (b) fruit-localized phytochromes are not global regulators of ripening, but instead regulate one or more specific components of this developmental process.
authors.affiliation: Department of Botany, The University of Georgia, Athens 30602, USA.
authors.forename: R
authors.initials: R
authors.lastname: Alba
authors.forename: M M
authors.initials: MM
authors.lastname: Cordonnier-Pratt
authors.forename: L H
authors.initials: LH
authors.lastname: Pratt
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D005030:Ethylenes / Q000096:biosynthesis*; D005638:Fruit / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D000077276:Lycopene; D018551:Solanum lycopersicum / Q000378:metabolism*; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D005030:Ethylenes; D012333:RNA, Messenger; D010834:Phytochrome; D002338:Carotenoids; C036216:ethylene; D000077276:Lycopene