Immunolocalization of a cell wall β-galactosidase reveals its developmentally regulated expression in Cicer arietinum and its relationship to vascular tissue

We report the generation of antibodies against a beta-galactosidase from Cicer arietinum, beta IV-Gal, and the subsequent immunolocalization of the protein in different parts and developmental stages of the plant. The beta IV- Gal protein is encoded by the CanBGal-4 gene, which belongs to a family of at least four beta-galactosidase genes, transcripts of which were previously reported to be mainly present in seedling epicotyls and plant stem, its transcription pattern being inversely related to elongation rate of these organs. beta IV-Gal protein was detected in the cell walls of seedling epicotyls and plant stems. The immunodetection of beta IV-Gal protein in the cell wall protein extracts from aged epicotyls and basal stem internodes, both undergoing low rates of elongation, is in agreement with the trend of the CanBGal-4 transcript and indicates a relationship of this cell wall protein with the end of cell elongation. The specific main location of the beta IV-Gal protein in vascular tissue of epicotyls and stems and in a layer of sclerenchymatic cells surrounding the vascular cylinder (perivascular fibers) allows us to postulate a function for this beta-galactosidase in the modification of cell wall polymers during the development of cells of the vascular system. The localization of the beta IV-Gal protein also in the cell walls of collenchyma cells in internodes is consistent with the involvement of beta IV-Gal in cell wall modifications that lead to thick cell walls, such as in vascular cells.