title: Yolk proteins in the male reproductive system of the fruit fly Drosophila melanogaster: spatial and temporal patterns of expression.
abstract: In insects, spermatozoa develop in the testes as clones of single spermatogonia covered by specialized somatic cyst cells (cc). Upon completion of spermatogenesis, spermatozoa are released to the vas deferens, while the cc remain in the testes and die. In the fruit fly Drosophila melanogaster, the released spermatozoa first reach the seminal vesicles (SV), the organ where post-testicular maturation begins. Here, we demonstrate the temporal (restricted to the evening and early night hours) accumulation of membranous vesicles containing proteins in the SV lumen of D. melanogaster. When SV vesicles were isolated from the semen and co-incubated with testis-derived spermatozoa in vitro, their contents bound to the spermatozoa along their tails. The proteins of the SV vesicles were then characterized using 2-D electrophoresis. We identified a prominent protein spot of around 45-47 kDa, which disappears from the SV vesicles in the night, i.e. shortly after they appear in the SV lumen. Sequencing of peptides derived from this spot by mass spectrometry revealed identity with three yolk proteins (YP1-3). This unexpected result was confirmed by western blotting, which demonstrated that SV vesicles contain proteins that are immunoreactive with an antibody against D. melanogaster YP1-3. The expression of all yp genes was shown to be a unique feature of testis tissues. Using RNA probes we found that their transcripts localize exclusively to the cc that cover fully developed spermatozoa in the distal part of each testis. Temporally, the expression of yp genes was found to be restricted to a short period during the day and is followed by the evening accumulation of YP proteins in the cc. Immunohistochemical staining confirmed that cc are the source of SV vesicles containing YPs that are released into the SV lumen. These vesicles interact with spermatozoa and as a result, YPs become extrinsic proteins of the sperm membrane. Thus, we describe for the first time the expression of yolk proteins in the male reproductive system of D. melanogaster under physiological conditions, and show that somatic cells of the testes are the source of these proteins.
authors.affiliation: Department of Animal Physiology, Zoological Institute, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: mmajewska@biol.uw.edu.pl.
authors.forename: Magdalena M
authors.initials: MM
authors.lastname: Majewska
authors.affiliation: Department of Animal Physiology, Zoological Institute, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: asuszczynska@biol.uw.edu.pl.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Suszczynska
authors.affiliation: Department of Animal Physiology, Zoological Institute, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: askako@biol.uw.edu.pl.
authors.forename: Joanna
authors.initials: J
authors.lastname: Kotwica-Rolinska
authors.affiliation: Department of Animal Physiology, Zoological Institute, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: tomasz.czerwik@biol.uw.edu.pl.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Czerwik
authors.affiliation: Laboratory of Electron and Confocal Microscopy, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: bataki@biol.uw.edu.pl.
authors.forename: Bohdan
authors.initials: B
authors.lastname: Paterczyk
authors.affiliation: Department of Animal Physiology, Zoological Institute, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: martap@biol.uw.edu.pl.
authors.forename: Marta A
authors.initials: MA
authors.lastname: Polanska
authors.affiliation: Department of Paleobiology and Evolution, Faculty of Biology, University of Warsaw, CNBC (Cent 3), 101 Zwirki i Wigury Str., 02-089 Warsaw, Poland. Electronic address: p.p.bernatowicz@uw.edu.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Bernatowicz
authors.affiliation: Department of Animal Physiology, Zoological Institute, Faculty of Biology, University of Warsaw, 1 Miecznikowa Str., 02-096 Warsaw, Poland. Electronic address: piotrbe@biol.uw.edu.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Bebas
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004527:Egg Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D005786:Gene Expression Regulation; D008297:Male; D012669:Seminal Vesicles / Q000737:chemistry / Q000378:metabolism; D013091:Spermatogenesis; D013094:Spermatozoa / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D013737:Testis / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D014819:Vitellogenins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D004527:Egg Proteins; D014819:Vitellogenins; C105973:YP1 protein, Drosophila; C070799:YP3 protein, Drosophila; C101545:yolk protein 2, Drosophila
keywords: Cyst cells; Drosophila melanogaster; Seminal plasma; Seminal vesicles; Testis; Yolk proteins