Subcellular location of Arabidopsis thaliana subfamily a1 β-galactosidases and developmental regulation of transcript levels of their coding genes.

The aim of this work is to gain insight into the six members of the a1 subfamily of the β-galactosidases (BGAL) from Arabidopsis thaliana. First, the subcellular location of all these six BGAL proteins from a1 subfamily has been established in the cell wall by the construction of transgenic plants producing the enhanced green fluorescent protein (eGFP) fused to the BGAL proteins. BGAL12 is also located in the endoplasmic reticulum. Our study of the AtBGAL transcript accumulation along plant development indicated that all AtBGAL transcript appeared in initial stages of development, both dark- and light-grown seedlings, being AtBGAL1, AtBGAL2 and AtBGAL3 transcripts the predominant ones in the latter condition, mainly in the aerial part and with levels decreasing with age. The high accumulation of transcript of AtBGAL4 in basal internodes and in leaves at the end of development, and their strong increase after treatment both with BL and H3BO3 point to an involvement of BGAL4 in cell wall changes leading to the cease of elongation and increased rigidity. The changes of AtBGAL transcript accumulation in relation to different stages and conditions of plant development, suggest that each of the different gene products have a plant-specific function and provides support for the proposed function of the subfamily a1 BGAL in plant cell wall remodelling for cell expansion or for cell response to stress conditions.