Functional Divergence of the Glutamine Phosphoribosyl Pyrophosphate Amidotransferase (ASE) Gene Family in Arabidopsis

Background: Functional divergence occurs widely among duplicated genes in plants. The divergence of functional genes may result from changes in gene regulation or protein-coding regions, or both. These changes contributing to the functional divergence of plants require further elucidation. Glutamine phosphoribosyl pyrophosphate amidotransferase (ASE) is a key enzyme in de novo purine biosynthesis and plays important roles in plant growth and development. Results: In our research, three ASE genes were identified in the Arabidopsis thaliana genome, and they were designated AtASE1, AtASE2 and AtASE3. Gene expression profiles revealed that the three genes exhibit very different expression, and gene regulation plays a pivotal role in the divergence of the ASE gene family. Subcellular localization analysis indicated that the three proteins were all localized in chloroplasts. Protein biochemical analysis revealed that the catalytic abilities of ASE proteins show differentiation, but further transgenic overexpression experiments proved that this was not the main reason for physiological functional divergence. Conclusions: Our results indicate that the functional divergence of the ASE gene family members might result from changes in their promoters, but not protein-coding region.