The sex determination cascades in insects are diversified at the top of the cascade, where different primary molecular signals are employed, while at the bottom of the cascades, particularly the doublesex genes, are highly conserved. Here, we identified the doublesex ortholog (Btau-dsx) of Bactrocera tau, a pumpkin fruit fly, and found that Btau-dsx is composed of six exons and five introns with an additional short "m" exon located in the second intron. Btau-dsx is different from its orthologs in most dipteran insects: Its pre-mRNA is sex-specifically spliced to yield three (two male and one female) instead of two transcript variants. The two deduced proteins produced by the male-specific transcripts are a functional (Btau-DSXM1) and a truncated (Btau-DSXM2) protein, while the female-specific transcript produces the functional Btau-DSXF protein. These three proteins contain all conserved domains except Btau-DSXM2 which has no OD2 domain. The female-specific transcript is detected in both fertilized and unfertilized eggs and in both somatic and germ cells of the adult females, while the male-specific transcript is detected only in fertilized eggs and in the abdominal tissues and testes of adult males. The presence of the Btau-dsxM1 transcript in fertilized eggs at the early syncytium stage suggests that in XY embryos, the Y-linked M factor gene may function quite soon after fertilization to alter the splicing pattern of Btau-dsx pre-mRNA from the female-specific to the male-specific mode. Injection of Btau-dsxF dsRNA into recently emerging females can reduce the expression of vitellogenin (Btau-Vg) and causes some defects in the ovaries, indicating that Btau-dsxF works upstream of Btau-Vg., Thanaset Thongsaiklaing, Hataichanok Passara, Mingkwan Nipitwathanaphon, Lertluk Ngersiri., and Obsahuje bibliografii
Bisexual gonads in the stoneflies Perla burimeisteriana, P. pallida and Dinocras cephalotes are reported for the first time. Gross morphology and ultrastructure of the accessory ovaries of mature larvae and adult males of Perla marginata are described in detail. There are 36-58 male ovarioles situated distal to the paired testes and opening into fused termini of the lateral ducts in abdominal segments II and III. These correspond in structure to the ovarioles of adult females but are significantly smaller (maximum size of proximal oocyte 9.0 × 45 µm) and each usually contains 10-14 linearly arranged previtellogenic oocytes. Oogenesis ceases at the end of previtellogenesis or at the onset of vitellogenesis. The ooplasm contains either regularly dispersed or irregularly accumulated particles in different regions of the cell with accumulations occurring near mitochondria and Golgi complexes. Based on results of metachromatic staining, these are thought to represent either lipid droplets (most) or yolk globules. The oolemma rarely develops short microvili and few pycnotic vesicles. Development of the follicular epithelium (influencing vitellogenesis and secretory activity during choriogenesis) is abnormal. Follicular cell growth is not synchronized with that of the oocytes, and the follicular cells of the terminal (distal) oocytes show neither patency nor secretory activity. The mechanism controlling degeneration of male ovarioles and the evolutionary significance of hermaphroditic gonads in the Plecoptera are discussed.
Although a monophyletic group, male (XX/XY) and female heterogametic (WZ/ZZ) sex chromosome systems with a couple of variants like XX/X, Z/ZZ and multiple sex chromosome systems occur in insects. Molecular and morphological differences between X and Y or W and Z range from imperceptible to conspicuous. This article illustrates sex chromosome differentiation mainly in two fly species, Drosophila melanogaster and Megaselia scalaris, and in Lepidoptera. The earliest phases of XY evolution are present in the fly M. scalaris. Occasionally in this species, the male determining gene jumps to another chromosome, transforming the new host chromosome to a functional Y chromosome. Thus, in M. scalaris there are strains with virtually no XY differentiation (except for the sex determining function) and others with a moderate degree of differentiation. Base substitutions and alterations like sequence deletions, duplications, and insertions of mobile sequences mark the onset of molecular differentiation. Accumulation of molecular changes and coarser alterations are thought to lead to the morphological differences seen in WZ chromosome pairs of Lepidoptera. The W chromosome probably evolved in the most numerous clade of Lepidoptera, the Ditrysia, after it diverged from the common lepidopteran stem. Extant species display various degrees of molecular and morphological differentiation of the W chromosome, translocation or fusion with autosomes, and loss of the W.