The cytogenetic architecture of the aphid genome

Abstract

In recent years aphids, with their well-defined polyphenism, have become favoured as model organisms for the study of epigenetic processes. The availability of the pea aphid (Acyrthosiphon pisum) genome sequence has engendered much research aimed at elucidating the mechanisms by which the phenotypic plasticity of aphids is inherited and controlled. Yet so far this research effort has paid little attention to the cytogenetic processes that play a vital part in the organisation, expression and inheritance of the aphid genome. Aphids have holocentric chromosomes, which have very different properties from the chromosomes with localised centromeres that are found in most other organisms. Here we review the diverse forms of aphid chromosome behaviour that occur during sex determination and male and female meiosis, often in response to environmental changes and mediated by endocrine factors. Remarkable differences occur, even between related species, that could have significant effects on the inheritance of all or parts of the genome. In relation to this, we review the particular features of the distribution of heterochromatin, rDNA genes and other repetitive DNA in aphid chromosomes, and discuss the part that these may play in the epigenetic modification of chromatin structure and function.

A new butterfly species from south Russia revealed through chromosomal and molecular analysis of the Polyommatus (Agrodiaetus) damonides complex (Lepidoptera, Lycaenidae)

“…The latter is also known as “inverted meiosis” (see e.g. Heckman et al 2014, Manicardi et al 2015, Bogdanov 2016). Despite the difference in the interpretation (in fact despite the difference in the definition of conventional and inverted meiosis), both papers stress the significant distinction between the first and the second ways.…”

General trends of chromosomal evolution in Aphidococca (Insecta, Homoptera, Aphidinea + Coccinea)

“…One of the secondary spermatocytes (which includes autosomes only) is smaller in size and degenerates just after anaphase I. The second, larger spermatocyte gives origin to two sperms; both with one X-chromosome (see Manicardi et al 2015 and our Fig. 2).…”

Genomic and Cytogenetic Localization of the Carotenoid Genes in the Aphid Genome

“…The chromosome number and karyotype structure of aphids have been studied in a large number of species over the past few decades showing that chromosomal variations are relatively common within some species [Blackman, 1980;Manicardi et al, 2002Manicardi et al, , 2015aMonti et al, 2011Monti et al, , 2012aRivi et al, 2012Rivi et al, , 2013Mandrioli et al, 2014a]. This is not surprising since aphids have holocentric chromosomes with kinetic activity spread along the whole chromosome axis [Blackman, 1980].…”

“…The peach potato aphid Myzus persicae (Sulzer) is one of the most extensively studied aphid species in the world in terms of lifecycle, migration, population genetics, and cytogenetics, and several molecular and cytogenetic analyses have been performed in order to elucidate the structure of its genome and karyotype [Blackman, 1980;Manicardi et al, 2002Manicardi et al, , 2015aMonti et al, 2011Monti et al, , 2012aRivi et al, 2012Rivi et al, , 2013.…”