Determination of the relative expression levels of rubisco small subunit genes in Arabidopsis by rapid amplification of cDNA ends

Multigene families are common in higher organisms. However, due to the clos e similarities between members, it is often difficult to assess the individ ual contribution of each gene to the overall expression of the family, In A rabidopsis thaliana, there are four genes encoding the small subunits (SSU) of ribulose-1.5-bisphosphate carboxylase oxygenase (rubisco) whose nucleot ide sequences are up to 98.4% identical. In order to overcome the technical limitations associated with gene-specific probes (or primers) commonly use d in existing methods, we developed a new gene expression assay based on th e RACE (rapid amplification of cDNA ends) technique with a single pair of p rimers. With this RACE gene expression assay, we were able to determine the relative transcript levels between four Arabidopsis SSU genes. We found th at the relative SSU gene expression differed significantly between plants g rown at different temperatures. Our observation raises the possibility that an adaptation of rubisco to the environment may be achieved through the sp ecific synthesis of the SSU proteins, which is determined by the relative e xpression levels between the SSU genes. (C) 2001 Academic Press.