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

CRISTINA F. NARDI; NATALIA VILLARREAL; GUSTAVO MARTINEZ; MARCOS CIVELLO

San Luis

Congreso; SAIB; 2011

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 hydrolase domain, and a C-terminal domain considered as 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, to test the hypothesis that  the over-expression of a expansin CBM would bind cell wall sites and then interfere with cell wall degrading enzymes. A. thaliana plants were transformed and three homozygous lines were selected. An increase in the total amount of cell wall was observed, mainly 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. A tensile 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 lower pectin degradation and then producing a more extensible cell wall