The Sequence and Expression of theγ-VPE Gene, One Member of a Family of Three Genes for Vacuolar Processing Enzymes inArabidopsis thaliana

摘要

Vacuolar processing enzymes (VPEs) are responsible for the maturation of seed proteins. Southern blot analysis showed that a family of genes for VPEs inArabidopsis thalianawas composed of three genes, forα-VPE, rβ-VPE andγ-VPE, respectively. The gene forγ-VPE was isolated from a genomic library. It was composed of nine exons and eight introns. The positions of the introns were fully conserved among the three genes, with the exception that theα-VPE gene was missing the fifth intron found in the rβ-VPE andγ-VPE genes. The predictedγ-VPE protein was 80and 57identical in terms of amino acid sequence to theα-VPE protein and rβ-VPE protein, respectively. Northern blot analysis demonstrated that theγ-VPE gene was expressed predominantly in the stems, with a lower level of expression in rosette and cauline leaves. However, the expression was not detected in roots, flowers plus buds, or green siliques, in contrast to the high-level expression of the rβ-VPE gene in the flowers plus buds. Thus,γ-VPE seems to be an isoform that is specific to vegetative organs. Members of the VPE family can be separated into two subfamilies, one that is specific to seeds and another that is specific to vegetative organs, such as leaves and stems. The members of the seed subfamily might function in the protein-storage vacuoles of seeds, while those of the vegetative subfamily might function in the lytic vacuoles of non-st