Chiyoko Tokunaga

Cell lineage and differentiation on the male foreleg of Drosophila melanogaster.

Abstract Cell lineage was studied in the epidermis of the basitarsus of the foreleg of male Drosophila melanogaster . This was accomplished by “marking” single cells, and their descendants, with genotypes different from the rest of the tissues. The mosaic basitarsi thus produced had areas with yellow chaetae on a background of black chaetae. On the basis of cell lineage data, the male basitarsus can be divided in two main parts. Region A occupies most of the segment including the primary sex comb and the central bristle. It does not include the area of the longitudinal rows 1, 2, and 3 and that of the secondary sex comb which shows a close developmental relation to rows 1 and 2. These areas constitute region B. Within region A cell lineage data yield a subdivision into A-1 which includes longitudinal row 1′, the transverse rows, longitudinal rows 7 and 6 and 5.5, the primary sex comb and the central bristle; and A-2 the remaining area which includes longitudinal rows 4 and 5. In region A-1 the following developmental relations were found. (a) The descendants of a yellow cell tend to form longitudinal strips of tissue both along the longitudinal rows and in the area of the transverse rows. (b) The proximal teeth of the sex comb and the central bristle are closely related to the posterior part of the transverse rows. (c) The middle teeth are closely related to the middle and the anterior parts of the transverse rows and to row 7. (d) The bractless bristles 5.5 are closely related to the distal teeth within the middle part of the sex comb. (e) The distal teeth of the sex comb are closely related to longitudinal row 6, and less closely, to row 7. The data suggest that the prospective area of the primary sex comb initially occupies the same distal part of the basitarsus as the most distal transverse rows of the female basitarsus. They suggest further that in the male the tissue of this area shifts anteriorly, whereby it changes its direction by approximately 90 degrees. This not only is deduced from the results of the cell lineage studies, but explains the position of the bracts at the base of the sex comb teeth and the direction assumed by the teeth, both of which deviate by about 90 degrees from that of the other chaetae of the segment. The above results on pure male basitarsi were confirmed by cell lineage studies of gynandric basitarsi. Systematic deviations from the norm in the location and direction of the male sex comb teeth and of female chaetae at the distal part of the segment are the result of the differential morphogenesis of the male and female tissues in this area.

THE DEVELOPMENTAL AUTONOMY OF EXTRA SEX COMBS IN DROSOPHILA MELANOGASTER.

Abstract In males of Drosophila melanogaster the first legs possess a sex comb, certain tibial transverse rows of bristles, and certain basitarsal transverse rows. These structures are absent on the second and third legs. The recessive autosomal mutant esc (extra sex comb) transforms certain features of the second and third into those of first legs. In different legs the transformation may be incomplete. The different parts may be transformed independently of each other, resulting in an array of partially transformed legs which are epigenetic mosaics of changed and unchanged areas. Genetic mosaics consisting of esc esc patches on esc + legs were obtained in consequence of X-ray induced somatic crossing over. By means of a translocation the esc esc areas were marked by genetically yellow pigmentation on the background of wild-type esc + . In the genetic mosaics esc acts autonomously in causing the appearance of sex combs and both types of transverse rows even in very small esc esc areas. Wild-type colored sex comb teeth on second and third legs were induced by X-ray irradiation of esc + males. The second legs of males with the combination esc D en +en of esc d , a dominant allele of esc, and en (engrailed) had a typical (primary) sex comb as well as the secondary comb normally placed by en on the first leg only. The gene esc as compared to esc+ controls the terminal pattern of leg differentiation by changing the competence of imaginal disk cells to respond to a prepattern that is alike for both alleles. The changed response consists in a tendency in certain areas toward growth in a transverse direction coupled with differentiation in a closely packed row, of bristles or teeth.

Determination of bristle direction in Drosophila

Abstract In Drosophila melanogaster the recessive mutant aristaless ( al ) leads to an abnormal orientation of the posterior scutellar bristles. The mutant also affects the shape of the dorsal scutellar surface. Heterozygous al + al flies show more than 10% penetrance in causing mutant-type bristle orientation. By means of genetic mosaics on the scutellum, caused by X-ray-induced somatic crossing-over and marked by areas of yellow pigmentation on a nonyellow background, it is shown that al autonomously leads to abnormal scutellar growth. Secondarily, in cases of such abnormal growth, an aristaless-type direction is imposed on the posterior scutellar bristle, regardless of its own al al or al + al genotype.

The effects of temperature and aging of Drosophila males on the frequencies of XXY and XO progeny

Abstract Drosophila males of the constitution y/y+Y were aged for 10 days at 25° and 10° and then mated daily for 13 days at 25° to virgin yw (XX) females. The total frequencies of exceptional XXY and XO offspring to which the father contributed either (a) both an X and a Y chromosome, or (b) neither of them, were highly significantly more numbers in the 7th- and 8th-day broods of the 10° than the 25° pre-aged series. In all experiments the frequency of paternal XO exceptions was greatly in excess of that of XXY exceptions. The data on brood patterns suggest that the stages most sensitive to the production of paternal exceptions by pre-aging at 10° are those of the primary spermatocytes. The same stages are also sensitive to low temperature induction of temporarily low fertility.

Intragenic somatic recombination in the lozenge cistron of Drosophila.

SummaryIn Drosophila melanogaster intragenic mitotic recombination between the two lozenge alleles, lz36 and lzy4, separated from each other by 0.14 meiotic recombination units, was observed. Among 48 725 females of the genotype w+lz36/w lzy4 which had been irradiated by a dose of 1000 r X-rays as larvae 41–47 hours after oviposition, a total of 11 faceted eye spots (not lz) were induced. All 11 spots were w+, none w. Possible reasons for the lack of the expected w, faceted spots were checked. Inversion of the X chromosome which would suppress recombination between the w and lz loci was not involved. Gene order of lz36-lzy4-kinetochore was confirmed by meiotic recombination test. Nonautonomy of lz gene action was not a factor, as tested by gynanders which showed that lzy4 and lzs were autonomous. Possibility of reverse mutation was not likely as shown by the large scale control experiments. Gene conversion is suggested as a likely mechanism for the lack of the expected w, faceted spots although the possibility of unequal crossing over induced by X-rays can not be excluded, nor can the preferential z-segregation hypothesis.

Nonautonomy in differentiation of pattern-determining genes in Drosophila. II. Transplantation of eyeless-dominant leg disks.

Abstract Mosaics consisting of tissue of normal genotype in the sex comb region of otherwise ey D males had shown nonautonomy of sex comb differentiation, i.e., production of multiple combs by not- ey D cells. In work reported in this paper, it was investigated whether the nonautonomy depends on local action of ey D in the first-leg imaginal disk or on an ey D substance produced elsewhere in the larval body. Disks of male first legs of y larvae 70 hours old were transplanted into ey D larvae of the same age. As controls, transplants were produced in the combination y to y , and ey D to y . Regardless of variability in the manifestation of the developmental capacity of transplants, the data obtained show clear-cut autonomy in differentiation of sex comb patterns of not- ey D tissue in ey D host and of ey D tissue in not- ey D host.

Genetic studies on Aphiochacta sp.

1. ノミバエの short arista (sa°) ストツクの起源, 形質及びこの表現に関与する変更因子の存在を推定した.2. sa°は第 III 染色体劣性因子による形質で, Delta と連関し, truncate や bar° は II 染色体に位置することを明らかにした.3. sa°の野生型に復帰する状態を調査し, 復帰野生型を生ずると同時に他の突然変異形質をも生ずること, 復帰野生型交配を継続して種々の突然変異を生じ, 再び sa 形質をも生ずる状態について述べた.4. 復帰野生型雄を sa 雌に交配すると, sa を伴性因子様に分離させる事実から, 更に伴性因子 Abrupt が復帰野生型雄との交配で常染色体因子様分離ををする事実を発見し, これが復帰野生型 Y 染色体の存在により起ることを確めた. これと同じ特性をもつ Y 染色体を sa1 や sa67 の再復帰 sa や一部の sa° がもつこと, sa°, sa°120, sa° より由来した b67 や Ab67, 野生型ストツクの Y 染色体にはこのような特性はないことを明らかにした. この特殊 Y 染色体の存在の Ab3b° ストツクの Ab の相手の X 染色体にある致死因子, sa1 の X 染色体にある半致死因子の効果は失われる特長がある.5. sa°, sa1, sa67 形質は対立因子関係にあると思われるが, これら相互の間の相異について述べた.6. 幼虫期以後 sa°, sa67 を18°Cで飼育して, 25°Cで飼育した対照に比し羽化個体の sa 表現度の低下を見たが, この操作では sa に因子的な変化は起らなかつたと考えられる.7. sa°, 復帰野生型, それから生じた突然変異体及び復帰野生型 Y 染色体をもつ Ab3b°雄等について, 主として幼虫神経節細胞の中期像での染色体異常を塗抹標本や切片で或は幼虫に冷却処理を行つて後調査したが, この像で見出される範囲の染色体異常は起つていなかつたと考えられる.8. ノミバエの性原細胞有糸分裂に見られる特異な相同染色体間の親和性について述べ, これと同様に somatic pairing が幼虫神経節細胞の有糸分裂にも見られること, 及びこの神経節細胞の分裂 prophase や metaphase に見られる染色体内の一定の非染色部について述べた. 精巣における減数分裂像の観察によつても復帰野生型や sa°等の染色体異常の発見は困難であつた.9. 復帰野生型の特殊な Y 染色体の遺伝行動を説明する為に, ノミバエでは Y 染色体に強力な雄性決定因子がありこの作用で性決定が行われると仮定し, 復帰野生型等の特殊 Y 染色体は第 III染色体と強力な雄性決定因子をもつ Y 染色体部分との間に転座が起つたもので, この特殊 Y 染色体をもつ個体では第 III 染色体が通常の場合の性染色体となつたものとして説明を試みた. sa° の複雑な復帰現象や頻繁な突然変異形質の変化については, 遺伝子の変化によるのでなく染色体異常によることを暗示した.