Increases in cell elongation, plastid compartment size and phytoene synthase activity underlie the phenotype of the high pigment-1 mutant of tomato

• Published in: Planta 2003-10, Vol.217 (6), p.896-903
• Main Authors: Cookson, P.J, Kiano, J.W, Shipton, C.A, Fraser, P.D, Romer, S, Schuch, W, Bramley, P.M, Pyke, K.A
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; alkyl (aryl) transferases; Alkyl and Aryl Transferases - genetics; Alkyl and Aryl Transferases - metabolism; Base Sequence; Biological and medical sciences; Carotenoids; Carotenoids - metabolism; cell growth; chlorophyll; Chlorophyll - metabolism; Chlorophylls; Chloroplasts; Chromoplasts; diploidy; DNA Primers; Economic plant physiology; Enzymatic activity; enzyme activity; Flowers & plants; Fructification and ripening; Fructification, ripening. Postharvest physiology; Fruits; fruits (plant anatomy); Fundamental and applied biological sciences. Psychology; gene expression; Geranylgeranyl-Diphosphate Geranylgeranyltransferase; Growth and development; leaves; Lycopersicon esculentum - genetics; Lycopersicon esculentum - growth & development; Lycopersicon esculentum - ultrastructure; Mesophyll cells; molecular sequence data; mutants; nucleotide sequences; Oxidoreductases - genetics; Oxidoreductases - metabolism; Pericarp; Phenotype; Phenotypes; phytoene synthase; Pigmentation; plant anatomy; Plant cells; plant development; Plant Leaves - enzymology; Plant physiology and development; plant pigments; plant proteins; Plants; plastid compartment; Plastids; Plastids - ultrastructure; Polymerase Chain Reaction; Seeds - physiology; Solanum lycopersicum var. lycopersicum; Tomatoes; vegetables; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-003-1065-9

A characteristic trait of the high pigment-1 (hp-1) mutant phenotype of tomato (Lycopersicon esculentum Mill.) is increased pigmentation resulting in darker green leaves and a deeper red fruit. In order to determine the basis for changes in pigmentation in this mutant, cellular and plastid development was analysed during leaf and fruit development, as well as the expression of carotenogenic genes and phytoene synthase enzyme activity. The hp-1 mutation dramatically increases the periclinal elongation of leaf palisade mesophyll cells, which results in increased leaf thickness. In addition, in both palisade and spongy mesophyll cells, the total plan area of chloroplasts per cell is increased compared to the wild type. These two perturbations in leaf development are the primary cause of the darker green hp-1 leaf. In the hp-1 tomato fruit, the total chromoplast area per cell in the pericarp cells of the ripe fruit is also increased. In addition, although expression of phytoene synthase and desaturase is not changed in hp-1 compared to the wild type, the activity of phytoene synthase in ripe fruit is 1.9-fold higher, indicating translational or post-translational control of carotenoid gene expression. The increased plastid compartment size in leaf and fruit cells of hp-1 is novel and provides evidence that the normally tightly controlled relationship between cell expansion and the replication and expansion of plastids can be perturbed and thus could be targeted by genetic manipulation.