Evolutionary study of duplications of the miRNA machinery in aphids associated with striking rate acceleration and changes in expression profiles.

Background: The sequencing of the genome of the pea aphid Acyrthosiphon pisum revealed an unusual expansion of the miRNA machinery, with two argonaute-1, two dicer-1 and four pasha gene copies. In this report, we have undertaken a deeper evolutionary analysis of the phylogenetic timing of these gene duplications and of the associated selective pressures by sequencing the two copies of ago-1 and dcr-1 in different aphid species of the subfamily Aphidinae. We have also carried out an analysis of the expression of both copies of ago-1 and dcr-1 by semi-quantitative PCR in different morphs of the pea aphid life cycle.

Combination of molecular data support the existence of three main lineages in the phylogeny of aphids (Hemiptera: Aphididae) and the basal position of the subfamily Lachninae.

The first molecular studies on the phylogeny of aphids (Hemiptera: Aphididae) bumped into a striking lack of phylogenetic structure for taxa levels higher than tribe, probably as a consequence of the rapid adaptive radiation that this group of insects went through during the Late Cretaceous. Here we present a new attempt to infer the relationships between major aphid taxa by the separate and combined analysis of two nuclear sequences (the long-wavelength opsin gene and the elongation factor 1 alpha gene) and two mitochondrial sequences (the genes encoding the subunit 6 of the F-ATPase and the subunit II of the cytochrome oxidase). Our results confirm previous results with the grouping of the subfamilies analysed in three main lineages, that are named A+D (subfamilies Aphidinae, Calaphidinae, Chaitophorinae, Drepanosiphinae and Pterocommatinae), E+T (subfamilies Anoeciinae, Eriosomatinae, Hormaphidinae, Mindarinae and Thelaxinae) and L (subfamily Lachninae).

Molecular systematics of aphids (Homoptera: Aphididae): new insights from the long-wavelength opsin gene.

Viviparous aphids (Aphididae) constitute a monophyletic group within the Homoptera with more than 4000 extant species worldwide but higher diversity in temperate regions. Several aspects of their biology account for attention paid to this group of insects. Their plant-sap-sucking way of feeding with many species transmitting viruses to crop plants has important implications on crop management strategies.