beta-xylosidase activity and expression of a B-xylosidase gene during strawberry fruit ripening.

MARTÍNEZ GA; CHAVES AR; PEDRO MARCOS CIVELLO

PLANT PHYSIOLOGY AND BIOCHEMISTRY

Elsevier Science

Año: 2004 vol. 42 p. 89 - 96

0981-9428

Strawberry fruit shows a marked softening during ripening and the processis associated with an increment of pectin solubility and a reduction of themolecular mass of hemicelluloses. In this work, we report the activity of β-xylosidase and the expression of a β-xylosidase gene in strawberry fruit. We havecloned a cDNA fragment encoding a putative β-xylosidase (FaXyl1) from acDNA library obtained from ripe strawberry fruit. The analysis of the deducedamino acid sequence revealed that FaXyl1 is closely related to other β-xylosidasesfrom higher plants. The expression of FaXyl1 was strongly associated to thereceptacle tissue although a low expression level was detected in achenes andovaries. The accumulation of FaXyl1 mRNA is ripening-related, starting in whitefruit, reaching the maximum at 25-50% red fruit and decreasing thereafter. Thetotal β-xylosidase enzyme activity was detected in all ripening stages with themaximum in 25-50% red fruit. The low activity level detected in immature stages,where no expression of FaXyl1 was found, suggests the presence of other β-xylosidases-like genes. Both the expression of FaXyl1 and the total β-xylosidaseactivity were down regulated by auxins, as occurs for most of the ripening-relatedprocesses in strawberry fruit. A putative role of FaXyl1 and β-xylosidase isdiscussed.