Portiera as a phylogenetic tool on whiteflies

Whiteflies (Sternorrhyncha: Aleyrodidae) are a group of small phloem-feeding insects which includes several important agricultural pests. In contrast to other insect groups, whiteflies taxonomy is based on nymphal stages morphology. However, this stage shows phenotypic plasticity, complicating the classification. In fact, several authors have proposed revisions in whiteflies taxonomy, especially in ranks above species.Whiteflies have specialized cells that harbor an obligatory/primary bacterial endosymbiont named 'Candidatus Portiera aleyrodidarum', which complements the insect's diet with essential amino acids. Portiera has been vertically transmitted since the divergence of whiteflies (circa 160 Mya) from their Psyllinea ancestor, and therefore reflects its host phylogeny (co-evolution). In contrast to the genome stasis showed by three Portiera lineages, the Portiera lineage in Bemisia tabaci presents an uncommon genome instability (rearrangements), probably due to the loss of the DNA polymerase proofreading sub-unit (dnaQ). Our main goal here was to improve whiteflies classification by establishing a phylogenetic framework based on several Portiera genes. In addition, we followed divergence time and the rise, in Portiera, of genomic instability (by tracing the presence/absence of dnaQ and several genomic rearrangements).