Galacturonosyltransferase 4 silencing alters pectin composition and carbon partitioning in tomato

FABIANA DE GODOY; LUISA BERMÚDEZ; BRUNO SILVESTRE LIRA; AMANDA PEREIRA DE SOUZA; PAULA ELBL; DIEGO DEMARCO; SALEH ALSEEKH; MARINA INSANI; MARCOS BUCKERIDGE; JULIANA ALMEIDA; GRIGIONI G; ALISDAIR ROBERT FERNIE; FERNANDO CARRARI; MAGDALENA ROSSI

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2013 vol. 68 p. 2449 - 2466

0022-0957

Pectin is a main component of the plant cell wall and is the most complex family of polysaccharides in nature. Itscomposition is essential for the normal growth and morphology pattern, as demonstrated by pectin-defective mutantphenotypes. Besides this basic role in plant physiology, in tomato, pectin structure contributes to very importantquality traits such as fruit firmness. Sixty-seven different enzymatic activities have been suggested to be required forpectin biosynthesis, but only a few genes have been identified and studied so far. This study characterized the tomatogalacturonosyltransferase (GAUT) family and performed a detailed functional study of the GAUT4 gene. The tomatogenome harbours all genes orthologous to those described previously in Arabidopsis thaliana, and a transcriptionalprofile revealed that the GAUT4 gene was expressed at higher levels in developing organs. GAUT4-silenced tomatoplants exhibited an increment in vegetative biomass associated with palisade parenchyma enlargement. Silencedfruits 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 consequenceof the reduction in the fruit weight and number. Altogether, these results suggest that, beyond its role in pectinbiosynthesis, GAUT4 interferes with carbon metabolism, partitioning, and allocation. Hence, this cell-wall-relatedgene seems to be key in determining plant growth and fruit production in tomato.