Insects use hydrocarbons as cuticular waterproofing agents and as contact pheromones. Although their biosynthesis from fatty acyl precursors is well established, the last step of hydrocarbon biosynthesis from long-chain fatty aldehydes has remained mysterious. We show here that insects use a P450 enzyme of the CYP4G family to oxidatively produce hydrocarbons from aldehydes. Oenocyte-directed RNAi knock-down of Drosophila CYP4G1 or NADPH-cytochrome P450 reductase results in flies deficient in cuticular hydrocarbons, highly susceptible to desiccation, and with reduced viability upon adult emergence. The heterologously expressed enzyme converts C 18 -trideuterated octadecanal to C 17 -trideuterated heptadecane, showing that the insect enzyme is an oxidative decarbonylase that catalyzes the cleavage of long-chain aldehydes to hydrocarbons with the release of carbon dioxide. This process is unlike cyanobacteria that use a nonheme diiron decarbonylase to make alkanes from aldehydes with the release of formate. The unique and highly conserved insect CYP4G enzymes are a key evolutionary innovation that allowed their colonization of land. Insects are the largest group of extant terrestrial organisms. As their crustacean ancestors moved from aquatic to terrestrial environments, insects were confronted with a new, dry frontier. Insects solved the ecophysiological problem of how to restrict water loss to prevent dessication by depositing long-chain hydrocarbons as essential waterproofing components on their epicuticle (1). These diverse chemicals now serve many additional functions, particularly in defense, reproduction, and communication (2). In flies, cuticular hydrocarbons (CHs) are a complex blend of long-chain (∼C21-C37+) alkanes and alkenes that serve as species-and sex-specific semiochemicals, and some components are sex pheromones. CHs also serve in nest mate recognition by social insects and as trail pheromones in ants; the complexity of their blend can be useful in taxonomic discrimination of mosquitoes. Much is known about the biosynthesis of CHs from fatty acids in insects, involving a complex network of fatty acid synthases, elongases, and desaturases, leading to very long-chain acyl-CoA thioesters. These are converted by acyl-CoA reductases to aldehydes that serve as substrates for the last oxidative decarbonylation step (2) (Fig. 1). The single carbon chain-shortening conversion of precursor aldehydes to hydrocarbons is catalyzed by a P450 enzyme, P450hyd, with release of CO 2 (3), but this enzyme has not yet been identified. The only known decarbonylase that has recently been described occurs in cyanobacteria that use a nonheme diiron enzyme (4-8) to catalyze the last step (Fig. 1). Insect CH are synthesized in large ectodermally derived cells (9) called oenocytes (10-12), and are then shuttled by hemolymph lipophorin (13,14) to the cuticle, where they are deposited on the outer epicuticular layer. Here we identify P450hyd as CYP4G1 in Drosophila melanogaster, and show that the enzyme is massively coexpresse...

SignificanceMany insects release volatile terpenes for chemical communication. However, the biosynthetic origin and evolution of these infochemicals are mostly unknown. We show that the harlequin bug, Murgantia histrionica, a stink bug pest (Hemiptera) of crucifer crops, produces a terpene aggregation pheromone by an enzyme that is unrelated to microbial and plant terpene synthases. M. histrionica terpene synthase activity is highly sex- and tissue-specific and makes a sesquiterpene alcohol, so far unknown in animals, as pheromone precursor. The enzyme evolved from ancestral isoprenyl diphosphate synthases and provides new evidence for de novo biosynthesis of terpenes in hemipteran insects. Knowledge of pheromone biosynthesis in stink bugs may lead to the development of new controls of these pests.

Maternal placentophagy, although widespread among mammals, is conspicuously absent among humans cross-culturally. Recently, however, advocates for the practice have claimed it provides human postpartum benefits. Despite increasing awareness about placentophagy, no systematic research has investigated the motivations or perceived effects of practitioners. We surveyed 189 females who had ingested their placenta and found the majority of these women reported perceived positive benefits and indicated they would engage in placentophagy again after subsequent births. Further research is necessary to determine if the described benefits extend beyond those of placebo effects, or are skewed by the nature of the studied sample.

Pets increasingly serve the function as emotional surrogates of children, with tremendous resources poured into their care. However, this function of pets may be quite different from the typical human-pet dynamics characterizing a wider array of societies. To help fill a gap in the cross-cultural understanding of pets, we employed the probability sample of the electronic Human Relations Area Files (eHRAF), covering 60 societies, to code for various features of human-pet dynamics. The findings revealed that dogs are the most commonly kept pets, followed by birds, cats, and other animals including horses, rodents, and reptiles. Dogs, cats, and other pets frequently served valuable functions such as aiding in hunting and pest removal. Birds, dogs, and some other pets also served as playthings, particularly the young of these animals and for the enjoyment of human children. Feeding, sleeping, and positive and negative interactions varied across societies and pets. Dogs, cats, birds, and other pets were frequently killed-and sometimes eaten-and dogs frequently subject to physical abuse. These data illustrate both similarities and differences cross-culturally in human-pet dynamics as well as many stark contrasts with how pets such as dogs in the US are treated today.

BackgroundThe mountain pine beetle (Dendroctonus ponderosae) is a significant coniferous forest pest in western North America. It relies on aggregation pheromones to colonize hosts. Its three major pheromone components, trans-verbenol, exo-brevicomin, and frontalin, are thought to arise via different metabolic pathways, but the enzymes involved have not been identified or characterized. We produced ESTs from male and female midguts and associated fat bodies and used custom oligonucleotide microarrays to study gene expression patterns and thereby made preliminary identification of pheromone-biosynthetic genes.ResultsClones from two un-normalized cDNA libraries were directionally sequenced from the 5' end to yield 11,775 ESTs following sequence cleansing. The average read length was 550 nt. The ESTs clustered into 1,201 contigs and 2,833 singlets (4,034 tentative unique genes). The ESTs are broadly distributed among GO functional groups, suggesting they reflect a broad spectrum of the transcriptome. Among the most represented genes are representatives of sugar-digesting enzymes and members of an apparently Scolytid-specific gene family of unknown function. Custom NimbleGen 4-plex arrays representing the 4,034 tentative unique genes were queried with RNA from eleven different biological states representing larvae, pupae, and midguts and associated fat bodies of unfed or fed adults. Quantitative (Real-Time) RT-PCR (qRT-PCR) experiments confirmed that the microarray data accurately reflect expression levels in the different samples. Candidate genes encoding enzymes involved in terminal steps of biosynthetic pathways for exo-brevicomin and frontalin were tentatively identified.ConclusionsThese EST and microarray data are the first publicly-available functional genomics resources for this devastating forestry pest.