title: Galacturonosyltransferase 4 silencing alters pectin composition and carbon partitioning in tomato.
abstract: Pectin is a main component of the plant cell wall and is the most complex family of polysaccharides in nature. Its composition is essential for the normal growth and morphology pattern, as demonstrated by pectin-defective mutant phenotypes. Besides this basic role in plant physiology, in tomato, pectin structure contributes to very important quality traits such as fruit firmness. Sixty-seven different enzymatic activities have been suggested to be required for pectin biosynthesis, but only a few genes have been identified and studied so far. This study characterized the tomato galacturonosyltransferase (GAUT) family and performed a detailed functional study of the GAUT4 gene. The tomato genome harbours all genes orthologous to those described previously in Arabidopsis thaliana, and a transcriptional profile revealed that the GAUT4 gene was expressed at higher levels in developing organs. GAUT4-silenced tomato plants exhibited an increment in vegetative biomass associated with palisade parenchyma enlargement. Silenced fruits showed an altered pectin composition and accumulated less starch along with a reduced amount of pectin, which coincided with an increase in firmness. Moreover, the harvest index was dramatically reduced as a consequence of the reduction in the fruit weight and number. Altogether, these results suggest that, beyond its role in pectin biosynthesis, GAUT4 interferes with carbon metabolism, partitioning, and allocation. Hence, this cell-wall-related gene seems to be key in determining plant growth and fruit production in tomato.
authors.affiliation: Departamento de Botânica-IB-USP, 277, 05508-900, São Paulo, SP, Brazil.
authors.forename: Fabiana
authors.initials: F
authors.lastname: de Godoy
authors.forename: Luisa
authors.initials: L
authors.lastname: Bermúdez
authors.forename: Bruno Silvestre
authors.initials: BS
authors.lastname: Lira
authors.forename: Amanda Pereira
authors.initials: AP
authors.lastname: de Souza
authors.forename: Paula
authors.initials: P
authors.lastname: Elbl
authors.forename: Diego
authors.initials: D
authors.lastname: Demarco
authors.forename: Saleh
authors.initials: S
authors.lastname: Alseekh
authors.forename: Marina
authors.initials: M
authors.lastname: Insani
authors.forename: Marcos
authors.initials: M
authors.lastname: Buckeridge
authors.forename: Juliana
authors.initials: J
authors.lastname: Almeida
authors.forename: Gabriela
authors.initials: G
authors.lastname: Grigioni
authors.forename: Alisdair Robert
authors.initials: AR
authors.lastname: Fernie
authors.forename: Fernando
authors.initials: F
authors.lastname: Carrari
authors.forename: Magdalena
authors.initials: M
authors.lastname: Rossi
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry; D003001:Cloning, Molecular; D005638:Fruit / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D017343:Genes, Plant / Q000235:genetics / Q000502:physiology; D018551:Solanum lycopersicum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018613:Microscopy, Confocal; D010368:Pectins / Q000032:analysis / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D037941:Silencer Elements, Transcriptional / Q000235:genetics / Q000502:physiology; D014574:Uronic Acids / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D014574:Uronic Acids; D010368:Pectins; D001205:Ascorbic Acid
keywords: Solanum pennellii; fruit metabolism; galacturonic acid; galacturonosyltransferase; pectin; tomato.