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Mito-nuclear coadaptation in bivalves with doubly uniparental inheritance of mitochondria may rely on alternative splicing
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Edité par CCSD -
International audience. Mito-nuclear incompatibilities (MNIs) can lead to a desynchronization of the machinery required for efficient cellular energy production (oxydative phosporylation OXPHOS). Therefore, coevolution and coadaption of mitochondrial and nuclear genes involved in this mechanism are primordial. In species with doubly uniparental inheritance (DUI) of mitochondria such as Limecola balthica, both males and females are able to transmit their mitochondria, the former to all their progeny and the latter to their male offspring, where the male mitogenomes (mt) are quartered in gametes. Two highly divergent mt-genome coexist within males, likely to disrupt mito-nuclear coadaptation. RNA-seq data from somatic tissues and purified gametes from 2 males and 2 females were produced to test if mitotype-specific nuclear alleles, paralogous nuclear genes or alternative splicing could play a role in mito-nuclear coadaptation. Differential expression profiles showed oocyte specificity but also high variability between replicates. The atp5c1 gene coding for the gamma subunit of the ATP-synthase FO/F1 complex, presented 9 isoforms which contained overall 32 different exons. These isoforms were composed of 10 to 21 exons and were differentially expressed between sexes. Sex-specific exons were genetically very close. Inferring the tertiary structure of these isoforms revealed that sex-specific exons are likely in direct interaction with a mt-encoded subunit of the ATP-synthase. These results suggest the existence of a mutually exclusive alternative splicing mechanism in the expression of atp5c1 between males and females. Additional analyses will be performed on additional samples and the other genes involved in the OXPHOS chain to test for the presence of alternative splicing.
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