The putative glutamate receptor 3.2 from Arabidopsis thaliana (AtGLR3.2) is an integral membrane peptide that accumulates in rapidly growing tissues and persists in vascular-associated tissues

Abstract

The accumulation and localization of the transcript and peptide corresponding to the gene that encodes the putative glutamate receptor isoenzyme 3.2 in Arabidopsis thaliana ( AtGLR3.2) is reported. Polyclonal antibodies, raised to the C-terminal region of AtGLR3.2, were used to determine that the putative plant glutamate receptor is an integral membrane protein with an apparent molecular weight of 111±1 kDa. RNA blot analysis revealed temporal accumulation of the AtGLR3.2 transcript in developing seedlings, results that were confirmed by polymerase chain reaction with reverse transcriptase-polymerase chain reaction (RT-PCR). Accumulation of the AtGLR3.2 transcript was highest in rapidly dividing tissues. Immunoblot analysis established that the presence of the AtGLR3.2 peptide mirrored, in most cases, the accumulation of the AtGLR3.2 transcript and suggests that AtGLR3.2 peptide accumulation is controlled in part by gene expression or RNA turnover. Affinity purified antibodies were used to localize the AtGLR3.2 protein in thin tissue sections. Immunohistochemical staining was intense and generalized in the rapidly dividing tissues of the developing floral buds, but mostly confined to the vascular tissue of the more mature hypocotyl, leaf and floral shoot tissues. Localization of the AtGLR3.2 protein to the rapidly growing tissues and vascular tissues is consistent with its proposed role in the translocation of calcium.