beta-galactosidases with a lectin-like domain are expressed in strawberry

Strawberry fruits (Fragaria x ananassa Duch.) undergo a marked softening du ring their ripening, and the process is accompanied by a release of free su gars with galactose among them. In this work total beta -galactosidase acti vity was measured in cell wall proteins from strawberry fruits at different developmental stages. Three full-length cDNAs (Fa beta gal1, Fa beta gal2 and Fa beta gal3, respectively) encoding different beta -galactosidases (EC 3.2.1.23) were isolated from a library representing red fruit transcripts. All of them could be detected both in fruits and in vegetative tissues. Ho wever, only Fa beta gal1 showed an increasing expression during the ripenin g stages up to a maximum in the red fruits, while the other two (Fa beta ga l2 and Fa beta gal3) were mostly found in green fruits and became barely de tectable during ripening proper. The three beta -galactosidase-encoding cDN As; were expressed in the yeast Pichia pastoris, and it was thus possible t o demonstrate that each of them encode a beta -galactosidase. The expressio n of the three beta -galactosidase genes appears to be downregulated by aux in, as already observed for other ripening-related genes of the non-climact eric strawberry. An unusual characteristic of two strawberry beta -galactos idases (Fa beta gal1 and Fa beta gal2) is that at the C-terminus of the enz ymes a domain is found which is structurally related to known animal peptid es with a sugar-binding ability.