Comprehensive survey of developmental genes in the pea aphid, Acyrthosiphon pisum: frequent lineage‐specific duplications and losses of developmental genes

Abstract

Abstracti mb_944 47..62Aphids exhibit unique attributes, such as polyphenisms and specialized cells to house endosymbionts, that make them an interesting system for studies at the interface of ecology, evolution and development. Here we present a comprehensive characterization of the developmental genes in the pea aphid, Acyrthosiphon pisum, and compare our results to other sequenced insects. We investigated genes involved in fundamental developmental processes such as establishment of the body plan and organogenesis, focusing on transcription factors and components of signalling pathways. We found that most developmental genes were well conserved in the pea aphid, although many lineage-specific gene duplications and gene losses have occurred in several gene families. In particular, genetic components of transforming growth factor beta (TGFb) Wnt, JAK/STAT (Janus kinase/signal transducer and activator of transcription) and EGF (Epidermal Growth Factor) pathways appear to have been significantly modified in the pea aphid.

Identification and embryonic expression of Wnt2, Wnt4, Wnt5 and Wnt9 in the millipede Glomeris marginata (Myriapoda: Diplopoda)

“…1). The other previously studied Wnt genes also cluster with their orthologs supporting earlier phylogenetic analysis (Janssen et al 2010). Altogether, there is little doubt about Wnt gene orthology, and the newly isolated gene fragments where thus designated as Glomeris Wnt2 (Gm-Wnt2), Wnt4 (Gm-Wnt4), Wnt5 (Gm-Wnt5) and Wnt9 (Gm-Wnt9).…”

“…Seven of them, i.e. wg/Wnt1, Wnt6,Wnt7,Wnt8,Wnt11,Wnt16 and WntA have previously been described and isolated by means of RT-PCR with degenerate primers (Janssen et al 2004(Janssen et al , 2010. At least four Wnt genes, however, remained undetected in these PCR screens, but have been detected in a sequenced embryonic transcriptome (see Experimental Procedures section).…”

Posterior localization of ApVas1 positions the preformed germ plasm in the sexual oviparous pea aphid Acyrthosiphon pisum

“…For detecting the expressions of Apvas mRNA and protein, we synthesized antisense riboprobes of Apvas1 - 4 and antibodies against ApVas1-4, respectively. Among the four Apvas genes, Apvas1 is the sole germline marker throughout viviparous development while expressions of Apvas2 - 4 are not germline specific (Additional file 2: Figure S2) [2,42]. We therefore examined the expression of Apvas1 in the sexual phase, assuming that it was also a germline marker in the oviparous embryos.…”

“…One issue, developmental plasticity, has long been a difficult subject to access in animal models displaying little phenotypic plasticity. However, the pea aphid Acyrthosiphon pisum , a hemimetabolous hemipteran insect with abundant adaptive capacity in response to specific environmental cues, has proven an excellent model for study, and the recently published genome has made research on this species more accessible [1,2]. With a sequenced genome, scientists can start exploring - at molecular and systematic levels - how and why a genome can direct the alteration of phenotypic and reproductive traits by stimuli from outside.…”

The evolution of dorsal–ventral patterning mechanisms in insects

“…Since it has been shown already that BMP signaling has self-regulatory properties in the Tribolium germband embryo (van der Zee et al 2006), it is tempting to speculate that this property of BMP signaling is used to regenerate the missing halves of the fragmented cricket germbands. Interestingly, while some of the critical factors of the vertebrate BMP self-regulatory system are missing from the Drosophila genome (e.g., BAMBI, ADMP, Noggin, and Gremlin), orthologs of these factors are present in the genomes of more basally branching insect species Shigenobu et al 2010;Werren et al 2010;JA Lynch, unpubl.). It will be interesting to see whether these genes participate in regulative processes of more basally branching insect species, and whether the loss of BMP signaling components is correlated with a reduced regulative capacity in the lineage leading to Drosophila.…”