Expression of the and Genes in Fruits.

Mexico is the center of origin and the leading exporter of papaya () to the United States of America and Canada. The changes in the fruit's firmness during ripening result from the action of several enzymes implicated in the synthesis/hydrolysis of cell wall polysaccharides. A vast family of genes encodes xyloglucan endotransglucosylase/hydrolase (XTH) enzymes, which act on cellulose-bound xyloglucan bonds. There are few reports on the action of the and genes; therefore, their participation in the fruit development and maturity processes has yet to be fully known. The expression levels of the and genes, and their correlation with firmness, at different stages of development and ripening of the fruit were determined in this work. The and genes reached their highest expression level during fruit development. These results suggest that these genes are activated in papaya mainly during fruit development to encode the enzymes that allow cell growth and maintain fruit firmness. These findings could be used to target papaya breeding texture quality and the speed of fruit growth.