Highlights d Novel aphid bicycle genes contribute to plant gall development d Variation in a bicycle gene alters plant gene expression and a gall phenotype d bicycle genes encode a large family of diverse, secreted, cysteine-rich proteins d Many bicycle genes have experienced repeated diversifying selection

Highlights d Expression changes in a Hox gene correlate with loss of pigmentation in D. santomea d Restoring Hox expression to D. santomea does not restore pigmentation phenotype d Changes throughout a downstream Hox-regulated network mask effects of Hox evolution d Hox-regulated traits evolve by small steps distributed throughout entire networks

Evolutionary shifts in plant -herbivore interactions provide a model for understanding the link among the evolution of behaviour, ecological specialization and incipient speciation. Drosophila mojavensis uses different host cacti across its range, and volatile chemicals emitted by the host are the primary cue for host plant identification. In this study, we show that changes in host plant use between distinct D. mojavensis populations are accompanied by changes in the olfactory system. Specifically, we observe differences in olfactory receptor neuron specificity and sensitivity, as well as changes in sensillar subtype abundance, between populations. Additionally, RNA-seq analyses reveal differential gene expression between populations for members of the odorant receptor gene family. Hence, alterations in host preference are associated with changes in development, regulation and function at the olfactory periphery.

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Several evolutionary forces are thought to maintain genetic variation for fitness-related traits, such as lifespan, but experimental support is limited. Using a powerful experimental design, we identified lifespan-associated variants by exposing outbred Drosophila melanogaster to standard and high-sugar diets and tracking genome-wide allele frequency changes as the flies aged. We mapped alleles associated with early vs late life tradeoffs, late-onset effects, and genotype-by-environment (GxE) interactions - all of which are predicted by long-standing theories to maintain genetic variation for lifespan. We also validated an environmentally-dependent role for nAChRalpha4 in regulating lifespan; the ortholog of this gene is one of the few lifespan-associated genes in humans (CHRNA3). Our results provide insight into the highly polygenic and context-dependent genetic architecture of lifespan, as well as the evolutionary processes that shape this key trait.

In an elaborate form of inter-species exploitation, many insects hijack plant development to induce galls, novel plant organs resulting from dramatic reprograming of plant cell biology. Insects induce galls by introducing unidentified molecules into plants. Here we identify an aphid gene, determinant of gall color (dgc), that is genetically associated with variation in a gall phenotype, providing the first example of an insect gene implicated in gall development. Dgc encodes a BICYCLE protein, a new family of secreted proteins. Bicycle genes are strongly expressed specifically in galling aphid salivary glands, suggesting they control many aspects of gall development. Bicycle genes have experienced unusually strong diversifying selection, consistent with their potential role controlling gall development in a molecular arms race between aphids and their host plants.

Two photos in figure 3a in a recent paper [1], intended to represent Z stacks of Or59b-expressing cells, were inserted incorrectly. The corrected panel is included here. Reference 1. Crowley-Gall A, Date P, Han C, Rhodes N, Andolfatto P, Layne JE, Rollamnn SM. 2016 Population differences in olfaction accompany host shift in Drosophila mojavensis.