Characterization of GPR1/FUN34/YaaH proteins and acetate metabolism in the microalga Chlamydomonas reinhardtii

The green microalga C. reinhardtii has been widely adopted as a model to study the dynamic metabolism of photosynthetic organisms. The successful research in the last decades has provided significant advances in understanding the regulation of carbon metabolism in this facultative photo-autotrophic model, however, the process of metabolite transport across the membranes remains poorly described. In particular, although the exchanges occurring between the intracellular compartments account for the majority of total transport, the characterization of membrane proteins in this alga is very limited. In this work, we investigated general aspects of acetate metabolism in C. reinhardtii and the characterization of five genes coding proteins belonging to the GPR1/FUN34/YaaH (GFY) family. Here, we provide several lines of evidence to implicate CrGFY1-5 as channels which share structural homology with bacterial succinate-acetate channels and specifically localize to microbodies, which are surprisingly distinct from the glyoxylate cycle-containing peroxisomal microbodies. In silico structural models, gene expression profiling, and in vivo fluorescence localization of all five isoforms support this role and also argue in favor of possible redundant functions. The additional parts of this work present different analyses related to acetate metabolism aspects investigated through the use of the toxic analogous fluoroacetate, the cellular fitness during anaerobic period and the acetate-dependent lipid accumulation along with other physiological analyses