Impairment of cytotype regulation of P-element activity in Drosophila melanogaster by mutations in the Su(var)205 gene.

Cytotype regulation of transposable P elements in the germ line of Drosophila melanogaster is associated with maternal transmission of P elements inserted at the left telomere of the X chromosome. This regulation is impaired in long-term stocks heterozygous for mutations in Suppressor of variegation 205 [Su(var)205], a gene implicated in the control of telomere length. Regulation by TP5, a structurally incomplete P element at the X telomere, is more profoundly impaired than regulation by TP6, a different incomplete P element inserted at the same site in a TAS repeat at the X telomere. Genetic analysis with the TP5 element indicates that its regulatory ability is not impaired in flies whose fathers came directly from a stock heterozygous for a Su(var)205 mutation, even when the flies themselves carry this mutation. However, it is impaired in flies whose grandfathers came from such a stock. Furthermore, this impairment occurs even when the Su(var)205 mutation is not present in the flies themselves or in their mothers. The impaired regulatory ability of TP5 persists for at least several generations after TP5 X chromosomes extracted from a long-term mutant Su(var)205 stock are made homozygous in the absence of the Su(var)205 mutation. Impairment of TP5-mediated regulation is therefore not directly dependent on the Su(var)205 mutation. However, it is characteristic of the six mutant Su(var)205 stocks that were tested and may be related to the elongated telomeres that develop in these stocks. Impairment of regulation by TP5 is also seen in a stock derived from Gaiano, a wild-type strain that has elongated telomeres due to a dominant mutation in the Telomere elongation (Tel) gene. Regulation by TP6 is not impaired in the Gaiano genetic background. The regulatory abilities of the TP5 and TP6 elements are therefore not equally susceptible to the effects of elongated telomeres in the mutant Su(var)205 and Gaiano stocks.

Sexual dimorphism in foot length proportionate to stature.

BACKGROUND: The preponderance of existing results suggests that, relative to stature, women have smaller feet than men. However, several investigations indicate that the relationship between foot length and stature may be curvilinear, a pattern that, due to the dimorphic nature of stature, would mask the true direction of pedal sexual dimorphism in published results. AIM: The study aimed to determine whether proportionate foot length is sexually dimorphic and, if so, the nature of that dimorphism. MATERIALS AND METHODS: Surveying genetically disparate populations (USA, Turkey, and Native North and Central American), we examined data from three previous anthropometric studies (Davis 1990, Parham et al. 1992, Ozaslan et al. 2003) and foot tracings from the Steggerda Collection at the US National Museum of Health and Medicine. Analyses explored sex differences in the ratio between foot length and stature, and tested for nonlinearity. RESULTS: Although varying in degree across populations, proportionate to stature, female foot length is consistently smaller than male foot length. CONCLUSION: Given the biomechanical challenges posed by pregnancy, smaller female proportionate foot length is somewhat surprising, as foot length affects dorsoventral stability. It is possible that the observed pattern reflects intersexual selection for small female foot size, a cue of youth and nulliparity.

Maternal transmission of P element transposase activity in Drosophila melanogaster depends on the last P intron.

Maternal transmission of RNAs or proteins through the egg cytoplasm plays an important role in eukaryotic development. We show that the transposase activity encoded by the P transposable element of Drosophila melanogaster is transmitted through the oocytes of females heterozygous for this element even when these oocytes do not carry the element itself. However, this maternal transmission is abolished when the last of three introns is removed from the P element. These facts imply that maternal transmission of transposase activity involves the RNA transcribed from the P element rather than the polypeptide it encodes, and that to be transmitted maternally, this RNA must possess the last intron. Examination of the intron's sequence reveals that it contains a motif of nine nucleotides that has been implicated in the maternal transmission of developmentally significant RNAs. This same intron limits expression of the P transposase to the germ line of Drosophila. Thus, the last P intron has two important biological functions.

A hobo transgene that encodes the P-element transposase in Drosophila melanogaster: autoregulation and cytotype control of transposase activity.

Drosophila were genetically transformed with a hobo transgene that contains a terminally truncated but otherwise complete P element fused to the promoter from the Drosophila hsp70 gene. Insertions of this H(hsp/CP) transgene on either of the major autosomes produced the P transposase in both the male and female germlines, but not in the soma. Heat-shock treatments significantly increased transposase activity in the female germline; in the male germline, these treatments had little effect. The transposase activity of two insertions of the H(hsp/CP) transgene was not significantly greater than their separate activities, and one insertion of this transgene reduced the transposase activity of P(ry(+), Delta2-3)99B, a stable P transgene, in the germline as well as in the soma. These observations suggest that, through alternate splicing, the H(hsp/CP) transgene produces a repressor that feeds back negatively to regulate transposase expression or function in both the somatic and germline tissues. The H(hsp/CP) transgenes are able to induce gonadal dysgenesis when the transposase they encode has P-element targets to attack. However, this ability and the ability to induce P-element excisions are repressed by the P cytotype, a chromosomal/cytoplasmic state that regulates P elements in the germline.

Regulation of P-element transposase activity in Drosophila melanogaster by hobo transgenes that contain KP elements.

Fusions between the Drosophila hsp70 promoter and three different incomplete P elements, KP, SP, and BP1, were inserted into the Drosophila genome by means of hobo transformation vectors and the resulting transgenic stocks were tested for repression of P-element transposase activity. Only the H(hsp/KP) transgenes repressed transposase activity, and the degree of repression was comparable to that of a naturally occurring KP element. The KP transgenes repressed transposase activity both with and without heat-shock treatments. Both the KP element and H(hsp/KP) transgenes repressed the transposase activity encoded by the modified P element in the P(ry(+), Delta2-3)99B transgene more effectively than that encoded by the complete P element in the H(hsp/CP)2 transgene even though the P(ry(+), Delta2-3)99B transgene was the stronger transposase source. Repression of both transposase sources appeared to be due to a zygotic effect of the KP element or transgene. There was no evidence for repression by a strictly maternal effect; nor was there any evidence for enhancement of KP repression by the joint maternal transmission of H(hsp/KP) and H(hsp/CP) transgenes. These results are consistent with the idea that KP-mediated repression of P-element activity involves a KP-repressor polypeptide that is not maternally transmitted and that KP-mediated repression is not strengthened by the 66-kD repressor produced by complete P elements through alternate splicing of their RNA.

Telomeric P elements associated with cytotype regulation of the P transposon family in Drosophila melanogaster.

P elements inserted at the left end of the Drosophila X chromosome were isolated genetically from wild-type P strains. Stocks carrying these elements were tested for repression of P-strain-induced gonadal dysgenesis in females and for repression of transposase-catalyzed P-element excision in males and females. Both traits were repressed by stocks carrying either complete or incomplete P elements inserted near the telomere of the X chromosome in cytological region 1A, but not by stocks carrying only nontelomeric X-linked P elements. All three of the telomeric P elements that were analyzed at the molecular level were inserted in one of the 1.8-kb telomere-associated sequence (TAS) repeats near the end of the X chromosome. Stocks with these telomeric P elements strongly repressed P-element excision induced in the male germline by a P strain or by the transposase-producing transgenes H(hsp/CP)2, H(hsp/CP)3, a combination of these two transgenes, and P(ry(+), delta2-3)99B. For H(hsp/CP)2 and P(ry(+), delta2-3)99B, the repression was also effective when the flies were subjected to heat-shock treatments. However, these stocks did not repress the somatic transposase activity of P(ry(+), delta2-3)99B. Repression of transposase activity in the germline required maternal transmission of the telomeric P elements themselves. Paternal transmission of these elements, or maternal transmission of the cytoplasm from carriers, both were insufficient to repress transposase activity. Collectively, these findings indicate that the regulatory abilities of telomeric P elements are similar to those of the P cytotype.