The expression of galectin-8 at various organs, its characterization through in silico analysis with possible anti-viral activity, was carried out from the grubs of Oryctes rhinoceros. Galectin-8 amplification, sequencing, prediction of amino acids, and analysis showed functional domains specific to galectin of several other species of insects. Further, quantification of galectin-8 transcripts revealed significantly higher levels of expression in hemocyte lysate than any other organs. The glycan lactose, that specifically inhibited the functional activity of galectin was used as a ligand for molecular docking, with a binding energy of -8.5 kcal/mol, revealing the specificity of lactose to galectin-8. MD simulation performed to find the binding stability disclosed the dynamic nature of galectin-8 and its targeted interaction with lactose. The protein-protein docking performed between galectin-8 with two dengue viral non-structural proteins, NS1 and NS5, suggested the possible antiviral property of galectin-8 against the dengue virus.

Abstract: The pseudostem weevil Odoiporus longicollis being a major pest of banana confers a serious loss to the crop. The cellulose- and terpene-laden diet demands a high reliance on gut microbiome to platter the nutrition. Here we investigated the whole microbiome of foregut, midgut and hindgut of O. longicollis to understand the spatial distribution of microbes. In bacteria, Firmicutes: Bacilli dominated the foregut and Proteobacteria: Gammaproteobacteria was highest in midgut and hindgut. Interestingly, Erysipelotrichia was comparatively much higher in hindgut. The Enterobacteriaceae subjugated the entire gut (Klebsiella and Enterobacter) with differential distribution of Raoultella, Citrobacter and Escherichia. This is followed by Lactobacillaceae (Leuconostoc, Lactiplantibacillus etc.) in foregut and Streptococcaceae (Lactococcus) in midgut and hindgut. The primary endosymbiont Candidatus Nardonella was found to be foregut-specific. In Fungi, Ascomycota and Basidiomycota were abundant. Foregut and hindgut had an abundance of Debaryomycetaceae (Scheffersomyces, Millerozyma and Candida) and the midgut had Saccharomycodaceae (Hanseniaspora and Yarrowia). Other eukaryotes i.e., Alveolata, Apicomplexa, Oomycota, Discoba, Amoebozoa, CS clade, Euglenozoa, Heterolobosea and Perkinsozoa were distributed differentially. Hindgut was determined to be a species-rich and diversified site for whole microbiome whereas for Fungi, foregut and midgut were species-rich sites, and hindgut and foregut had higher species diversity. Varying patterns of gene counts for carbohydrate metabolism, terpene degradation and nitrogen cycle were observed with particular significance in uncovering dependent and independent modes of cellulolysis in O. longicollis. The findings improved the understanding of site-specific diversity and richness of gut microbiome in O. longicollis to prospect for its control and management.

Cellulose, the substance that makes up most of a plant’s cell wall, is pondered to be one of the most abundant natural organic polymers on earth made up of glucose units linked by β-1, 4 glycosidic bonds. Insects possess cellulolytic system capable of producing variegate enzymes with multifarious specificities to break down complex lignocellulosic products. Astonishingly, endoglucanases, exoglucanase, and β-glycosidases act sequentially in a synergistic system to facilitate the breakdown of cellulose to utilizable energy source glucose. These extremely versatile enzymes are a better source in terms of environmental performance and overall energy efficiency. Pertaining to four main glycosyl hydrolase families (GHF), insect cellulases are distributed in all the insect orders explored up until now. In silico docking studies of endo-β-1,4-glucanase from 19 different insects belonging to six different orders identified that it possesses high affinity for all the six substrates, including CMC, cellulose, cellotriose, cellotetraose, cellopentose and cellohexaose. Additionally, β-glucosidase from nearly all the reported insect sources also showed considerable affinity towards cellobiose. Van der Waals, conventional hydrogen bonds, and carbon-hydrogen bonds stabilize the interaction between the enzyme and different substrates. Molecular dynamics simulations also held up the stability of various complexes. With lignocelluloses-based biofuels becoming a major focus of industrial and academic communities worldwide, this study can perhaps complement the propensity of insect cellulases for prospected applications.