The GPR1/FUN34/YaaH(/SatP) members in Chlamydomonas reinhardtii, are they novel peroxisomal transporters?

The green microalga C. reinhardtii can grow heterotrophically in presence of acetate in the dark as sole carbon source, due to the anaplerotic pathway of glyoxylate cycle1 almost completely localised in the peroxisomal microbodies2 . Despite the significant advances gained on carbon metabolism, the genes involved in acetate transport are not yet identified. Recently, five functionally uncharacterized members predicted to have transporter-like structure were classified within the protein family GPR1/FUN34/YaaH(/SatP) (GFY)3, which comprises genes coding for putative carboxylic acids transporters in other microorganisms, including acetate as substrate4. In C. reinhardtii, GFY1-5 as we shown by YFP fusion protein, localise to peroxisomal membranes. In addition, we also showed that these genes present distinct expression patterns in different cultivation conditions, which correlates with associated co-expressed genes found in the databases. Therefore, although these proteins share between 78 and 97% similarity between their amino acid sequences, this might suggest non-redundant roles. To gain insight on their role, we are currently analysing insertional and knock-down mutants. Mutants for the genes GFY1, GFY2 and GFY3 were obtained from the Chlamydomonas Library Project 5. Mutants for GFY4, GFY5 and all GFY genes are presently under generation via artificial micro RNA. In conclusion, GFY members could represent different protagonists in transporting substrates in/out of peroxisomal microbodies, as putative transporters/permeases function