BackgroundRelatively little is known about the genomic basis and evolution of wood-feeding in beetles. We undertook genome sequencing and annotation, gene expression assays, studies of plant cell wall degrading enzymes, and other functional and comparative studies of the Asian longhorned beetle, Anoplophora glabripennis, a globally significant invasive species capable of inflicting severe feeding damage on many important tree species. Complementary studies of genes encoding enzymes involved in digestion of woody plant tissues or detoxification of plant allelochemicals were undertaken with the genomes of 14 additional insects, including the newly sequenced emerald ash borer and bull-headed dung beetle.ResultsThe Asian longhorned beetle genome encodes a uniquely diverse arsenal of enzymes that can degrade the main polysaccharide networks in plant cell walls, detoxify plant allelochemicals, and otherwise facilitate feeding on woody plants. It has the metabolic plasticity needed to feed on diverse plant species, contributing to its highly invasive nature. Large expansions of chemosensory genes involved in the reception of pheromones and plant kairomones are consistent with the complexity of chemical cues it uses to find host plants and mates.ConclusionsAmplification and functional divergence of genes associated with specialized feeding on plants, including genes originally obtained via horizontal gene transfer from fungi and bacteria, contributed to the addition, expansion, and enhancement of the metabolic repertoire of the Asian longhorned beetle, certain other phytophagous beetles, and to a lesser degree, other phytophagous insects. Our results thus begin to establish a genomic basis for the evolutionary success of beetles on plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-1088-8) contains supplementary material, which is available to authorized users.

The aromatic polymer lignin protects plants from most forms of microbial attack. Despite the fact that a significant fraction of all lignocellulose degraded passes through arthropod guts, the fate of lignin in these systems is not known. Using tetramethylammonium hydroxide thermochemolysis, we show lignin degradation by two insect species, the Asian longhorned beetle (Anoplophora glabripennis) and the Pacific dampwood termite (Zootermopsis angusticollis). In both the beetle and termite, significant levels of propyl side-chain oxidation (depolymerization) and demethylation of ring methoxyl groups is detected; for the termite, ring hydroxylation is also observed. In addition, culture-independent fungal gut community analysis of A. glabripennis identified a single species of fungus in the Fusarium solani/Nectria haematococca species complex. This is a soft-rot fungus that may be contributing to wood degradation. These results transform our understanding of lignin degradation by wood-feeding insects.Asian longhorned beetle ͉ Pacific dampwood termite ͉ TMAH thermochemolysis ͉ Anoplophora glabripennis ͉ Zootermopsis angusticollis L ignin plays a central role in carbon cycling on Earth. Its heterogeneous structure imparts plants with structural rigidity and also serves to protect cellulose and hemicellulose from degradation (1). Most of what is known about lignin biodegradation is from pure culture studies with filamentous basidiomycete fungi, known as white-rot and brown-rot decay. Although both white-rot and brown-rot fungal degradation have been characterized, much more is known about the white-rot system (2, 3). White-rot fungi simultaneously degrade the three major components of the plant cell wall: lignin, cellulose, and hemicellulose. Analysis of white-rot-degraded wood shows that the reactions in lignin: (i) are oxidative, (ii) involve demethylation (or demethoxylation), (iii) include side-chain oxidation at C ␣ , and (iv) involve propyl side-chain cleavage between C ␣ and C ␤ (Fig. 1) (4). In contrast to white-rot fungi, brown-rot fungi are able to circumvent the lignin barrier, removing the hemicellulose and cellulose with only minor modification to the lignin. Consequently, lignin remains a major component of the degraded plant cell wall (5). The remaining lignin is demethylated on aryl methoxy groups and contains a greater number of ring hydroxyl groups (6).Little is known about lignin degradation in complex ecosystems, such as insect guts, where a consortium of microbes may be involved in degradation rather than just a single species. Although cellulose degradation in insect guts is well documented (7,8), the fate of lignin has not clearly been demonstrated (9, 10), and it is widely accepted that insect gut systems do not have the capacity to degrade lignin (10). Although the majority of previous reports suggest that many wood-feeding insects overcome the lignin barrier by feeding on predegraded wood (11) or through exosymbiotic relationships with wood-degrading fungi (12, 13), there are species of insects...

Bactrocera papayae Drew & Hancock, Bactrocera philippinensis Drew & Hancock, Bactrocera carambolae Drew & Hancock, and Bactrocera invadens Drew, Tsuruta & White are four horticultural pest tephritid fruit fly species that are highly similar, morphologically and genetically, to the destructive pest, the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). This similarity has rendered the discovery of reliable diagnostic characters problematic, which, in view of the economic importance of these taxa and the international trade implications, has resulted in ongoing difficulties for many areas of plant protection and food security. Consequently, a major international collaborative and integrated multidisciplinary research effort was initiated in 2009 to build upon existing literature with the specific aim of resolving biological species limits among B. papayae, B. philippinensis, B. carambolae, B. invadens and B. dorsalis to overcome constraints to pest management and international trade. Bactrocera philippinensis has recently been synonymized with B. papayae as a result of this initiative and this review corroborates that finding; however, the other names remain in use. While consistent characters have been found to reliably distinguish B. carambolae from B. dorsalis, B. invadens and B. papayae, no such characters have been found to differentiate the latter three putative species. We conclude that B. carambolae is a valid species and that the remaining taxa, B. dorsalis, B. invadens and B. papayae, represent the same species. Thus, we consider B. dorsalis (Hendel) as the senior synonym of B. papayae Drew and Hancock syn.n. and B. invadens Drew, Tsuruta & White syn.n. A redescription of B. dorsalis is provided. Given the agricultural importance of B. dorsalis, this taxonomic decision will have significant global plant biosecurity implications, affecting pest management, quarantine, international trade, postharvest treatment and basic research. Throughout the paper, we emphasize the value of independent and multidisciplinary tools in delimiting species, particularly in complicated cases involving morphologically cryptic taxa. Bactrocera (Bactrocera) dorsalis (Hendel)