Functional characterization of a Drosophila melanogaster mitochondrial deoxynucleotide transporter dRIM2.

We have studied the deoxynucleotide transport in Drosophila melanogaster. On the basis of homology with the S. cerevisiae RIM2 gene, encoding a pyrimidine deoxynucleotide carrier (Marrobbio et al. 2006), the CG18317 gene (dRIM2) in the fruit fly may code for a deoxynucleotide carrier. We demonstrated that Drosophila S2R+ cells, silenced for the dRIM2 expression, had a marked defect in the amounts of all mitochondrial dNTPs, both purines and pyrimidines. In vivo dRIM2 homozygous knockout produced a larval lethal phenotype. dRIM2-/- larvae showed (i) impairments in the locomotor behavior, (ii) a decrease in the rates of oxygen consumption and (iii) a depletion of the mtDNA. Following a detailed morphological characterization carried out in dRIM2-/- larvae evidenced an ongoing mitochondrial biogenesis accompanied by an alteration of mitochondria shaping. Additionally, the role of dRIM2 in the purine and pyrimidine metabolism was supported by a microarray analysis. We conclude that dRIM2 is a Drosophila deoxynucleotide carrier, essential for maintaining the mitochondrial functionality. Gene expression profiling was carried out on dRIM-/- and dRIM+/- Drosophila larvae using the Drosophila 1.0 custom platform (Agilent). Total RNA was obtained from the whole body of 3rd instar larvae for each genotype. Four and three biological replicates were analyzed for dRIM-/- and dRIM+/- samples respectively for a total of 7 microarray experiments.