A study of recombination, formation of chiasmata and synaptonemal complexes in female and male meiosis of Ephestia kuehniella (Lepidoptera)

Abstract

In female meiosis of Ephestia kuehniella no chiasmata can be detected during oogenesis and nurse-cell formation. The pachytene, which contains synaptonemal complexes, is transformed into metaphase I by shortening of the bivalents without an intermediary diplotene stage. Correspondingly, no crossing-over is found between the linked loci b and t, whereas recombination is normal (i.e. 50%) between the non-linked loci a and Us or b and Us, showing that no gross asymmetry exists in the reduction process of females. -Male meiosis on the other hand displays the normal sequence of prophase events. Synaptonemal complexes are present during the pachytene stage. Diplotene and diakinesis are present, characterized by typical meiotic configurations of bivalents, mostly containing one non-localized chiasma. Crossing-over between b and t occurs at a rate of 18.2% and 27.7% respectively in the male, probably depending on the derivation of the b-t-chromosome. -Except for the synaptonemal complexes, which are present in both sexes, the meiotic situation is thus the reverse of that in Drosophila with respect to the sexes: female meiosis is achiasmatic in Ephestia, male meiosis is chiasmatic with the expected genetic consequences.

Synaptonemal complexes in female and male meiotic prophase of Ephestia kuehniella (Lepidoptera)

“…1-6 in Table 2). These complements might belong to nuclei of nurse cells at the end of the pachytene stage, which differentiate after pachytene from oocytes by shortening of bivalents and their subsequent transformation into condensed metaphase-like structures (Traut, 1977;Guelin, 1975). Bivalents of most complements with the total length in the range of 280-3 50 m showed, similar to the early pachytene nuclei of males, relatively thick LEs (50-60 nm) but their other morphological characteristics varied.…”

“…Butter- microspreading, recombination nodules, synapflies and moths, with few exceptions, possess a WZ/ZZ chromosome mechanism of sex determination (Suomalainen, 1969a;Robinson, 1971). Females are the heterogametic sex displaying achiasmatic meiosis (Suomalainen, 1 969b;Traut, 1977). During oogenesis, eight sister germ cells are connected in a cluster and develop in parallel up to the pachytene stage.…”

“…After pachytene, seven cells are transformed into nurse cells and only one oocyte in a cluster completes meiosis. The SCs of the oocyte do not disintegrate but are transformed into modified SCs by shortening of the bivalents and retained to metaphase I (Rasmussen, 1976;Traut, 1977;Rasmussen & Hoim, 1982). According to Rasmussen (1977), these modified SCs serve as chiasma substitutes.…”

“…According to Rasmussen (1977), these modified SCs serve as chiasma substitutes. Male meiosis on the other hand is chiasmatic with a normal sequence of meiotic events including the process of recombination (Traut, 1977;Holm & Rasmussen, 1980).…”

A single major QTL controls expression of larval Cry1F resistance trait in Ostrinia nubilalis (Lepidoptera: Crambidae) and is independent of midgut receptor genes

“…The trait also was shown to be controlled by a single genetic locus that is inherited in a recessive fashion (Pereira et al 2008b). The sex determination system in O. nubilalis, and all Lepidoptera, is comprised of a homogametic sex chromosome pair in males (ZZ) and a heterogametic pair in females (ZW; Traut and Marec 1997), where achiasmatic females produce gametes that do not undergo meiotic recombination (Traut 1977). A biphastic linkage mapping approach was used as described by Heckel et al (1999) to establish pedigrees initiated from a single cross between a Cry1F resistant female (rr$; P rr$ ) 9 susceptible male (SS#; P SS# ), and subsequent backcross families were derived from an F 1 male 9 Bt resistant female (F 1rS# 9 BCP rr$ ; pedigree FQ4) or reciprocal F 1 female 9 resistant male (F 1rS$ 9 BCP rr# ; pedigree FQ5; Fig.…”