Most dominant roles of insect gut bacteria: digestion, detoxification, or essential nutrient provision?

BACKGROUND: The insect gut microbiota has been shown to contribute to the host's digestion, detoxification, development, pathogen resistance, and physiology. However, there is poor information about the ranking of these roles. Most of these results were obtained with cultivable bacteria, whereas the bacterial physiology may be different between free-living and midgut-colonizing bacteria. In this study, we provided both proteomic and genomic evidence on the ranking of the roles of gut bacteria by investigating the anal droplets from a weevil, Cryptorhynchus lapathi. RESULTS: The gut lumen and the anal droplets showed qualitatively and quantitatively different subsets of bacterial communities. The results of 16S rRNA sequencing showed that the gut lumen is dominated by Proteobacteria and Bacteroidetes, whereas the anal droplets are dominated by Proteobacteria. From the anal droplets, enzymes involved in 31 basic roles that belong to 7 super roles were identified by Q-TOF MS. The cooperation between the weevil and its gut bacteria was determined by reconstructing community pathway maps, which are defined in this study. A score was used to rank the gut bacterial roles. The results from the proteomic data indicate that the most dominant role of gut bacteria is amino acid biosynthesis, followed by protein digestion, energy metabolism, vitamin biosynthesis, lipid digestion, plant secondary metabolite (PSM) degradation, and carbohydrate digestion, while the order from the genomic data is amino acid biosynthesis, vitamin biosynthesis, lipid digestion, energy metabolism, protein digestion, PSM degradation, and carbohydrate digestion. The PCA results showed that the gut bacteria form functional groups from the point of view of either the basic role or super role, and the MFA results showed that there are functional variations among gut bacteria. In addition, the variations between the proteomic and genomic data, analyzed with the HMFA method from the point of view of either the bacterial community or individual bacterial species, are presented. CONCLUSION: The most dominant role of gut bacteria is essential nutrient provisioning, followed by digestion and detoxification. The weevil plays a pioneering role in diet digestion and mainly digests macromolecules into smaller molecules which are then mainly digested by gut bacteria.

Molecular characterization of diapause hormone and pheromone biosynthesis activating neuropeptide from the black-back prominent moth, Clostera anastomosis (L.) (Lepidoptera, Notodontidae).

Using a strategy of rapid amplification of cDNA ends, the cDNA of diapause hormone (DH) and pheromone biosynthesis activating neuropeptide (PBAN) was cloned from the head of Clostera anastomosis (L.). The Cloan-DH-PBAN cDNA contains an open reading frame encoding a 196-amino acid preprohormone, from which five putative FXPRL peptides, DH, PBAN, alpha-SGNP(SGNP, suboesophageal ganglion neuropeptide), beta-SGNP and gamma-SGNP, are released. Comparing the deduced amino acid sequences from cDNAs of these five FXPRL peptides to those known from other insects, Cloan-DH shows highest similarity of 93.1% to that from Agrotis ipsilon, Cloan-PBAN 93.9% to those from Helicoverpa armigera, Helicoverpa zea and Helicoverpa assulta, which show the highest similarity to species of Noctuidae. Phylogenetic analysis revealed that the Cloan-DH-PBAN gene is relatively closely related to those from Noctuoidea, but distant from those from Tortricoidea, Yponomeutoidea and Bombycoidea species. The DNA sequence encoding Cloan-DH-PBAN was cloned by PCR, which is 3698bp in size and comprises six exons interspersed by five introns. Developmental expression of the DH-PBAN transcripts in the head was also showed by a semi-quantitative RT-PCR method, which was relatively low in larvae and remained low in pupae of both sexes, increased sharply in adults of both sexes.