The Expression of a Novel Mitochondrially-Encoded Gene in Gonadic Precursors May Drive Paternal Inheritance of Mitochondria.
Mitochondria have an active role in germ line development, and their inheritance dynamics are relevant to this process. Recently, a novel protein (RPHM21) was shown to be encoded in sperm by the male-transmitted mtDNA of Ruditapes philippinarum, a species with Doubly Uniparental Inheritance (DUI) of mitochondria. In silico analyses suggested a viral origin of RPHM21, and we hypothesized that the endogenization of a viral element provided sperm mitochondria of R. philippinarum with the ability to invade male germ line, thus being transmitted to the progeny. In this work we investigated the dynamics of germ line development in relation to mitochondrial transcription and expression patterns using qPCR and specific antibodies targeting the germ line marker VASPH (R. philippinarum VASA homolog), and RPHM21. Based on the experimental results we conclude that both targets are localized in the primordial germ cells (PGCs) of males, but while VASPH is detected in all PGCs, RPHM21 appears to be expressed only in a subpopulation of them. Since it has been predicted that RPHM21 might have a role in cell proliferation and migration, we here suggest that PGCs expressing it might gain advantage over others and undertake spermatogenesis, accounting for RPHM21 presence in all spermatozoa. Understanding how foreign sequence endogenization and co-option can modify the biology of an organism is of particular importance to assess the impact of such events on evolution.
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Liliana
L
Milani
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Fabrizio
F
Ghiselli
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Andrea
A
Pecci
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Maria Gabriella
MG
Maurizii
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Marco
M
Passamonti
D000595:Amino Acid Sequence; D000818:Animals; D049872:Bivalvia / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D050259:Genes, Mitochondrial; D005819:Genetic Markers; D006066:Gonads / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D040582:Inheritance Patterns; D008297:Male; D008928:Mitochondria / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D038081:Organogenesis / Q000235:genetics; D016415:Sequence Alignment; D013091:Spermatogenesis / Q000235:genetics; D013094:Spermatozoa / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*
D005819:Genetic Markers