Beta-Xylosidase in strawberry fruit: Isolation of a full-lenght gene and analysis of tis expression and enzymatic activity in cultivars with contrasting firmess

BUSTAMANTE C.A.; ROSLI H.G.; AÑÓN M:C.; CIVELLO P.M; MARTINEZ G.A

PLANT SCIENCE

Año: 2006 vol. 171 p. 497 - 504

0168-9452

  Abstract Strawberry is a non-climateric fleshy fruit, which softens quickly and has short post-harvest life. Ripening is associated with an increment of pectin solubility and a reduction of the content of hemicelluloses. In this work, we have cloned the full-length cDNA encoding a β-xylosidase (FaXyl1) from Fragaria × ananassa and we have characterized its expression in two strawberry cultivars with contrasting fruit firmness. The analysis of the predicted protein showed that FaXyl1 is closely related to other β-xylosidases from higher plants. The recombinant protein obtained by over-expressing FaXyl1 in Escherichia coli had β-xylosidase activity against the artificial substrate p-nitrophenyl β-D-xilopyranoside. Differently from other bifunctional xylosidases, no α-L-arabinofuranosidase activity was detected in the recombinant enzyme. The expression of FaXyl1 gene was analyzed by northern-blot in Camarosa and Toyonaka strawberry cultivars, and compared with the corresponding protein data obtained by Western-blot and with the β-xylosidase activity during ripening. The softest cultivar (Toyonaka) showed an early accumulation of FaXyl1 transcript and a higher expression of the corresponding protein during ripening, which correlates with a higher β-xylosidase activity in all ripening stages analyzed. Keywords: Ripening; Softening; Cell wall; Fragaria