title: Complex and shifting interactions of phytochromes regulate fruit development in tomato.
abstract: Tomato fruit ripening is a complex metabolic process regulated by a genetical hierarchy. A subset of this process is also modulated by light signalling, as mutants encoding negative regulators of phytochrome signal transduction show higher accumulation of carotenoids. In tomato, phytochromes are encoded by a multi-gene family, namely PHYA, PHYB1, PHYB2, PHYE and PHYF; however, their contribution to fruit development and ripening has not been examined. Using single phytochrome mutants phyA, phyB1 and phyB2 and multiple mutants phyAB1, phyB1B2 and phyAB1B2, we compared the on-vine transitory phases of ripening until fruit abscission. The phyAB1B2 mutant showed accelerated transitions during ripening, with shortest time to fruit abscission. Comparison of transition intervals in mutants indicated a phase-specific influence of different phytochrome species either singly or in combination on the ripening process. Examination of off-vine ripened fruits indicated that ripening-specific carotenoid accumulation was not obligatorily dependent upon light and even dark-incubated fruits accumulated carotenoids. The accumulation of transcripts and carotenoids in off-vine and on-vine ripened mutant fruits indicated a complex and shifting phase-dependent modulation by phytochromes. Our results indicate that, in addition to regulating carotenoid levels in tomato fruits, phytochromes also regulate the time required for phase transitions during ripening.
authors.affiliation: Repository of Tomato Genomics Resources, Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India.
authors.forename: Suresh Kumar
authors.initials: SK
authors.lastname: Gupta
authors.forename: Sulabha
authors.initials: S
authors.lastname: Sharma
authors.forename: Parankusam
authors.initials: P
authors.lastname: Santisree
authors.forename: Himabindu Vasuki
authors.initials: HV
authors.lastname: Kilambi
authors.forename: Klaus
authors.initials: K
authors.lastname: Appenroth
authors.forename: Yellamaraju
authors.initials: Y
authors.lastname: Sreelakshmi
authors.forename: Rameshwar
authors.initials: R
authors.lastname: Sharma
mesh_terms: D053898:Biosynthetic Pathways / Q000235:genetics; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D005638:Fruit / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010834:Phytochrome / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D005030:Ethylenes; D012333:RNA, Messenger; D010834:Phytochrome; D002734:Chlorophyll; D002338:Carotenoids; C036216:ethylene
keywords: carotenoids; fruit ripening; photoreceptors