Influence of the carbohydrate-binding module of strawberry EXPANSIN2 on A. thaliana cell wall.

NARDI CRISTINA; VILLARREAL NATALIA; MARTÍNEZ GUSTAVO; CIVELLO PEDRO

Potrero de los Funes

Congreso; XLVII reunión anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2011

SAIB

Expansins are proteins involved in plant cell wall modifications. It has been described three domains in expansins, a signal peptide which directs the protein to the secretory pathway, a central glycosyl hydrolases domain, and a C-terminal domain that is considered a carbohydrate-binding module (CBM). The CBM would be anchoring the expansin to the cellulose surface, and the central domain would interact with hemicelluloses. In the present study, we have targeted the expression of the strawberry expansin2 CBM (CBM-FaEXP2) to A. thaliana cell walls, thus CBM-FaEXP2 would block the action sites of cell wall enzymes, avoiding their action. A. thaliana plants were transformed and three homozygous lines were selected. An increase in the total amount of cell wall was observed. This effect was due to an increase of pectin fraction, while cellulose and hemicelluloses fractions were not affected. Regarding the enzyme activities, there was a significant decrease in polygalacturonase, ß-galactosidase and xylosidase activities in transgenic lines. An extension analysis of the shoot showed that transgenic lines were more extensible than wild type. Our results support the hypothesis that CBM-FaEXP2 over-expression, would block the action of hydrolytic enzymes, leading to a less degradation of pectins and thus, producing a more extensible cell wall.