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First published online 22 April 2008
doi: 10.1242/jcs.025320
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Research Article |
1 Department of Genetics and Molecular Biology – "Sapienza" Università di Roma, 00185 Rome, Italy
2 Department of Evolutionary Biology, University of Siena, I-53100 Siena, Italy
* Author for correspondence (e-mail: roberto.piergentili{at}uniroma1.it)
Accepted 20 February 2008
Primary spermatocyte nuclei of Drosophila melanogaster contain three prominent lampbrush-like loops. The development of these structures has been associated with the transcription of three fertility factors located on the Y chromosome, named kl-5, kl-3 and ks-1. These loci have huge physical dimensions and contain extremely long introns. In addition, kl-3 and kl-5 were shown to encode two putative dynein subunits required for the correct assembly of the sperm axoneme. Here, we show that both the kl-5 and kl-3 loops are intensely decorated by monoclonal antibodies recognizing triple-stranded nucleic acids, and that each loop presents a peculiar molecular organization of triplex structures. Moreover, immunostaining of Drosophila hydei primary spermatocytes revealed that also in this species – which diverged from D. melanogaster 58 million years ago – Y-loops are decorated by anti-triplex antibodies, strongly suggesting a conserved role of loop-associated triplexes. Finally, we showed that in D. melanogaster wild-type lines that are raised at the non-permissive temperature of 31±0.5°C (which is known to induce male sterility in flies) both the triplex immunostaining and the axonemal dynein heavy chains encoded by kl-3 and kl-5 are no longer detectable, which suggests a functional correlation between loop-associated triplexes, the presence of axonemal proteins and male fertility in fly.
Key words: Lampbrush-like loops, Triplex, Heterochromatin, Y chromosome, Drosophila hydei
