During Drosophila spermatogenesis beta 1, beta 2 and beta 3 tubulin isotypes are cell-type specifically expressed but have the potential to coassemble into the axoneme of transgenic flies.
alpha and beta Tubulins exist in a number of different isotypes with distinct expression patterns during development. We have shown by immunofluorescent staining that beta 1, beta 2 and beta 3 tubulins are distributed very specifically in the testes of Drosophila. beta 3 Tubulin is present exclusively in cytoplasmic microtubules of cells somatic in origin, while the beta 1 isotype is localized in the somatic cells and in early germ cells of both the microtubules of the cytoskeleton as well as in the mitotic spindle. In contrast, beta 2 tubulin is present in all microtubular arrays (cytoskeleton, meiotic spindles, axoneme) of germ cells from meiotic prophase onward, though not detectable in somatic cells. Thus, a switch of beta tubulin isotypes from beta 1 to beta 2 occurs during male germ cell differentiation. This switch is also observed in the distantly related species Drosophila hydei. By fusing beta 1 or beta 3 amino acid coding regions to the control region of the beta 2 tubulin gene and performing germ line transformation experiments, we have examined the copolymerization properties of the different tubulin isotypes. Neither beta 1 nor beta 3 are detectable in the axoneme in the wild-type situation. Analysis of transgenic flies carrying beta 2-beta 1 fusion genes or beta 2-beta 3 fusion genes revealed that both beta 1 and beta 3 tubulin isotypes have the potential to co-incorporate with beta 2 tubulin into microtubules of the sperm axoneme. Male flies homozygous for the fusion genes (beta 2-beta 1 or beta 2-beta 3) remain fertile, despite the mixture of beta tubulin isotypes in the axoneme.
Kaltschmidt
B
B
Gentechnologische Arbeitsgruppe am Max-Planck-Institut für Biochemie, Martinsried/Bundesrepublik Deutschland.
Glätzer
K H
KH
Michiels
F
F
Leiss
D
D
Renkawitz-Pohl
R
R
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D000918:Antibody Specificity; D001483:Base Sequence; D003001:Cloning, Molecular; D004330:Drosophila; D008297:Male; D008648:Mesoderm / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D013082:Sperm Tail / Q000378:metabolism*; D013091:Spermatogenesis; D014404:Tubulin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D014404:Tubulin