Karyotype analysis of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae) reveals a large X chromosome with rRNA and histone gene families

Abstract

The Russsian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a worldwide pest of cereals. Despite its economic importance, little is known about its genome. Here we investigated physical genomic features in RWA by karyotype analysis using differential staining with AgNO(3), CMA(3), and DAPI, by chromosomal localization of ribosomal DNA (rDNA), H3 and H4 histone genes, and the "arthropod" telomeric sequence (TTAGG)(n) using fluorescence in situ hybridization (FISH), and by measuring the RWA genome size using flow cytometry. The female karyotype, 2n = 10, is composed of four autosome pairs and a pair of X chromosomes, whereas the male karyotype, 2n = 9, has a single X. The X chromosome is the largest element in the karyotype. All three molecular markers used, i.e., 18S rRNA and both H3 and H4 probes are co-localized at one end of the X chromosome. The FISH probes revealed that the AgNO(3)-positive bridge between two prometaphase X chromosomes of females, which is believed to be responsible for the elimination of one X chromosome in aphid oocytes determined to undergo male development, contains clusters of both histone genes, in addition to an rDNA cluster. Interestingly, RWA lacks the (TTAGG)(n) telomeric sequence in its genome, in contrast to several previously investigated aphid species. Additionally, we compared female and male genome sizes. The female genome size is 2C = 0.86 pg, whereas the male genome size is 2C = 0.70 pg. The difference between the DNA content in the two genders suggests that the RWA X chromosome occupies about 35% of the female haploid genome (1C = 0.43 pg), which makes it one of the largest sex chromosomes in the animal kingdom.

Cytogenetic Mapping of H1 Histone and Ribosomal RNA Genes in Hybrids between Catfish Species <b><i>Pseudoplatystoma corruscans</i></b> and <b><i>Pseudoplatystoma reticulatum</i></b>

“…This result confirmed that all individuals were hybrids and that each chromosome bearing associations of 18S/H1 was inherited from 1 specific parental species, which constitutes a conserved linkage group. In some invertebrate species, studies have demonstrated a common association of histone and ribosomal genes [Andrews et al, 1987;Cabrero et al, 2009;Roehrdanz et al, 2010;Novotná et al, 2011]. In fishes, although there are few studies about chromosome location of histone genes, the H1/5S association has already been described in Astyanax species [Hashimoto et al, 2011], and we have also reported the occurrence of H1/18S association in the 2 catfish species here.…”

Chromosomal evolutionary dynamics of four multigene families in Coreidae and Pentatomidae (Heteroptera) true bugs

“…A similar degree of conservation with two autosomal clusters (one bivalent) was also noticed in some Scarabaeinae beetles (Cabral-de-Mello et al 2011a) and in three species of aphids (Mandrioli and Manicardi 2013). Two clusters were also reported in the female of the aphid Diuraphis noxia (Aphididae), but they were located in the X chromosome (Novotná et al 2011). Considering the phylogenetic relationship of Heteroptera and Aphididae (Song et al 2012), it could be suggested that the number of clusters is conserved among these organisms, but the location is variable at the intra-and inter-chromosomal level in distinct species.…”

Chromosomal organization of the 18S and 5S rRNAs and histone H3 genes in Scarabaeinae coleopterans: insights into the evolutionary dynamics of multigene families and heterochromatin

“…Our results reinforce the idea that the association of the 5S rDNA and histone H3 clusters is not sporadic in coleopterans and that it appears to be common. Besides the association of 5S rDNA and histone H3 genes, co-localization or linked organization of major rDNA and histone genes were also reported in insect as described recently for example in Diuraphis noxia (Hemiptera) [50], Anthonomus grandis and A. texanus (Coleoptera) [51]. …”