Mutations in the neverland Gene Turned Drosophila pachea into an Obligate Specialist Species

Abstract

Most living species exploit a limited range of resources. However, little is known on how tight links build up during evolution between specialist species and the hosts they utilize. We examined the dependence of Drosophila pachea on its single host, the senita cactus. Several amino acid changes in the Neverland oxygenase rendered D. pachea unable to transform cholesterol into 7-dehydrocholesterol (first reaction in the steroid hormone biosynthetic pathway in insects) and thus made D. pachea dependent on the uncommon sterols of its host plant. The neverland mutations increase survival on the cactus unusual sterols and are in a genomic region that faced recent positive selection. This study illustrates how relatively few genetic changes in a single gene may restrict the ecological niche of a species.

Recurrent specialization on a toxic fruit in an island Drosophila population

“…The two peaks within the highly differentiated X-linked locus include genes controlling juvenile hormone and ecdysteroid signaling whose perturbation is a common target of plant defensive toxins (48,49). Mutations in genes affecting the ecdysteroid metabolism pathway have enhanced D. sechellia adaptation on toxic noni (20) and helped make Drosophila pachea an obligatory specialist on a toxic cactus (9). Another particularly intriguing candidate is the Osiris cluster associated with resistance to octanoic acid in D. sechellia (19).…”

“…However, ecological differences in preference for the degree of ripeness/decay exist, with species using less decaying material evolving capabilities to resist plant defensive toxins, digest living plant material, and detect the appropriate host and ripening stage (9)(10)(11)(12). Such an "ecological gradient" makes drosophilids ideal for the study of the genetic basis of dietary shifts.…”

Relaxed selective constraints drove functional modifications in peripheral photoreception of the cavefish P. andruzzii and provide insight into the time of cave colonization

“…In particular, two main hypotheses have been explored: first, positive selection directly eliminates traits, either because the reduction in function is itself beneficial or because it allows the preservation of energy (Protas et al, 2007;Lang et al, 2012); second, positive selection indirectly causes the loss of a trait as a byproduct of the gain of a new adaptive function, through mechanisms such as genetic hitchhiking or pleiotropy (Jeffery, 2009). It may be argued that the neutral scenario supported by our results as the most plausible explanation for the evolution of a 'blind' circadian clock does not definitively rule out alternative possibilities.…”

Hemimetabolous genomes reveal molecular basis of termite eusociality

“…In the synthesis of the moulting hormone, 20-hydroxyecdysone, the six Halloween genes (five cytochrome P450s and a Rieske-domain oxygenase) play a key role 48,49 . Only one Halloween gene, Shade (Shd; CYP314A1), which mediates the final step of 20-hydroxyecdysone synthesis, is differentially expressed between the final nymphal stages and adult females in B. germanica (Fig.…”