A family of β-galactosidase cDNAs related to development of vegetative tissue in Cicer arietinum

Abstract

In the cell wall of Cicer arietinum epicotyls, there are a family of b-galactosidases, one of them named bIII-Gal is a b-galactosidase able to degrade cell wall pectins. The role of the remainder b-galactosidases has not been established. In this paper, we describe the cloning and expression pattern of a family of three C. arietinum b-galactosidase cDNAs (named CanBGal-1, CanBGal-4 and CanBGal-5) and we compare these results with the previously characterized CanBGal-3 cDNA clone, which encode the bIII-Gal. The shared amino acid sequence identity among the four b-galactosidase deduced proteins (named b-Gal, bIII-Gal, bIV-Gal and bV-Gal) ranged from 63% to 81%. All display the putative active site of family 35 of the glycosyl hydrolases. An unusual characteristic of one of the chickpea b-galactosidases (bI-Gal) is the presence at the C-terminus of the enzyme of a galactose binding lectin domain. The CanBGals gene expression along seedlings and adult plant could suggests different roles of their corresponding protein throughout the chickpea plant. The expression of CanBGal-5 is related to young and meristematic stages with high cell division rate, such as the meristematic hook, very young epicotyls, and apical internodes. By contrast, CanBGal-1 and -4 seem to be more strongly related to advanced stages of epicotyl growth, increasing their expression along epicotyl age, and also in basal non-elongating stem internodes. In adult plants, CanBGal-1 shows its highest expression levels in leaves, while CanBGal-4 seems to be better represented in adult roots. This is the first report about several members of the genomic family of b-galactosidases acting during development of vegetative organs.