Evidence for dosage compensation in parthenogenetic Hymenoptera

Abstract

Amounts of DNA-Feulgen staining in individual somatic nuclei and mature sperm of the parthenogenetic wasps, Habrobracon juglandis, H. serinopae, and Mormoniella vitripennis, were determined with a scanning microdensitometer. The haploid genome for both species of Habrobracon was estimated to be 0.15-0.16 X 10-(12) gDNA, corresponding to a molecular weight of roughly 10 X10(10) daltons. The haploid genome of M. vitripennis is approximately twice this value, 0.33-0.34 X 10-(12) g, or about 20X10(10) daltons. Measurements made on dividing nuclei from syncytial preblastoderm embryos of H. juglandis and M. viripennis showed that the chromosomes of impaternate males were present in the haploid number and contained the C amount of DNA; whereas nuclei from female preblastoderm embryos contained the diploid number of chromosomes and the 2C amount of DNA. However, hemocyte and brain cell nuclei from either male or female adult wasps contained 2C and 4C amounts of DNA. Both sexes also showed equivalent levels of polyploidy (8C, 16C, or 32C) in Malpighian tubule nuclei. Therefore, in these parthenogenetic species,, a mechanism must exist the compensates during later development for the initial two-fold difference in the chromatin content of somatic nuclei in haploid male and diploid female embryos. Hemocytes from impaternate Mormoniella diploid males and triploid females contain the 2C and 3C amounts of DNA, respectively Therefore dosage compensation involves an additional cycle of DNA replication only in hapoid cells, and it insures that a certain minimum quantity of DNA is received by each somatic cell.

Epigenetic inheritance and genome regulation: is DNA methylation linked to ploidy in haplodiploid insects?

“…However, we must emphasize that these results are preliminary in nature, requiring additional study to resolve whether epigenetic information is functionally implicated in ploidy-associated regulatory compensation. One important consideration is that haploid males in Hymenoptera are known to compensate for lower genomic content relative to diploid females through endoreplication [6,9], wherein cells increase their genomic content without dividing [1]. Our results raise the possibility that epigenetic information similarly contributes to haploid regulatory compensation, particularly given that endoreplication is not ubiquitous among tissues [6].…”

“…In addition, members of different species sometimes vary in ploidy number. Such ploidy variation shapes molecular evolution, genetic interactions and gene function [5][6][7][8][9]. Thus, variation in ploidy fundamentally affects evolutionary and developmental processes.…”

“…Consequently, as many as 20% of all animal species may be haplodiploid [10]. Despite the taxonomic prevalence of haplodiploidy, the regulatory consequences of ploidy differences between sexes remain largely unknown (but see [6,9,11]). This lack of information represents a gap in our understanding of how biological systems respond to ploidy variation.…”

Impact of a selfish B chromosome on chromatin dynamics and nuclear organization in Nasonia

“…6F). We interpret these PSR clusters to be multiple chromosome copies due to the polyploid nature of these and other somatic cells in N. vitripennis (Rasch et al, 1977). A single region of PSR signal was detected in nearly all post-meiotic spermatids (n5206/210; Fig.…”

Single-locus sex determination in the parasitoid wasp Cotesia glomerata (Hymenoptera: Braconidae)

“…The basic number of chromosomes in C. glomerata revealed in the current study is the same as in many other braconid parasitoids, including Habrobracon (Bracon) hebetor Say (Torvik-Greb, 1935), H. pectinophorae Watanabe (Inaba cited in Mikino, a Data are given as a range from a minimum (where all undetermined males were considered haploid males) to a maximum (where all undetermined males were considered diploid males). (Rasch et al, 1977), Meteorus gyrator Thunberg (Gokhman and Quicke, 1995), M. pallipes Wesmael (Gokhman and Quicke, 1995) and the related species, C. congregate (Belle et al, 2002). Diploid males in some species with sl-CSD have a normal viability, although they can be either sterile (El Agoze et al, 1994;Krieger et al, 1999) or unable to fertilize females (Smith and Wallace, 1971;Naito and Suzuki, 1991).…”