In Cicer arietinum, as in several plant species, the β-galactosidases are encoded by multigene families, although
the role of the different proteins is not completely elucidated. Here, we focus in 2 members of this family, βIIIGal
and βIV-Gal, with high degree of amino acid sequence identity (81%), but involved in different developmental
processes according to previous studies. Our objective is to deepen in the function of these proteins by
establishing their substrate specificity and the possible alterations caused in the cell wall polysaccharides when
they are overproduced in Arabidopsis thaliana by constructing the 35S::βIII-Gal and 35S::βIV-Gal transgenic
plants.
βIII-Gal does cause visible alterations of the morphology of the transgenic plant, all related to a decrease in
growth at different stages of development. FTIR spectroscopy and immunological studies showed that βIII-Gal
causes changes in the structure of the arabidopsis cell wall polysaccharides, mainly a reduction of the galactan
side chains which is compensated by a marked increase in homogalacturonan, which allows us to attribute to
galactan a role in the control of the architecture of the cell wall, and therefore in the processes of growth. The
35S::βIV-Gal plants do not present any phenotypic changes, neither in their morphology nor in their cell walls. In
spite of the high sequence homology, our results show different specificity of substrate for these proteins, maybe
due to other dissimilar characteristics, such as isoelectric points or the number of N-glycosylation sites, which
could determine their enzymatic properties and their distinct action in the cell walls.
