First evidence of a horizontally‐acquired GH‐7 cellobiohydrolase from a longhorned beetle genome

Abstract

Xylophagous larvae of longhorned beetles (Coleoptera; Cerambycidae) efficiently break down polysaccharides of the plant cell wall, which make the bulk of their food, using a range of carbohydrate‐active enzymes (CAZymes). In this study, we investigated the function and evolutionary history of the first identified example of insect‐encoded members of glycoside hydrolase family 7 (GH7) derived from the Lamiinae Exocentrus adspersus. The genome of this beetle contained two genes encoding GH7 proteins located in tandem and flanked by transposable elements. Phylogenetic analysis revealed that the GH7 sequences of E. adspersus were closely related to those of Ascomycete fungi, suggesting that they were acquired through horizontal gene transfer (HGT) from fungi. However, they were more distantly related to those encoded by genomes of Crustacea and of protist symbionts of termites and cockroaches, supporting that the same enzyme family was recruited several times independently in Metazoa during the course of their evolution. The recombinant E. adspersus GH7 was found to primarily break down cellulose polysaccharides into cellobiose, indicating that it is a cellobiohydrolase, and could also use smaller cellulose oligomers as substrates. Additionally, the cellobiohydrolase activity was boosted by the presence of calcium chloride. Our findings suggest that the combination of GH7 cellobiohydrolases with other previously characterized endo‐β−1,4‐glucanases and β‐glucosidases allows longhorned beetles like E. adspersus to efficiently break down cellulose into monomeric glucose.

Insects Associated with the European Mistletoe (Viscum album) in Western Ukraine: a Pilot Study

“…Moreover, most of them cannot develop without the presence of fungal hyphae in the tissues of the host plant. Fungi play a very important role in the larval development and feeding of adults of many saproxylic insect species, and even in the evolution of their ability to decompose cellulose (Sasakura et al, 2022;Shin & Pauchet, 2023). In our study, the only fungal species we found was the parasitic fungus S. visci, of which numerous pycnidia were found on V. album specimens.…”

Functional carbohydrate-active enzymes acquired by horizontal gene transfer from plants in the whiteflyBemisia tabaci

“…The first plant cell wall degrading enzymes (PCWDEs) identified in an animal were ß-1,4-endoglucanases (or cellulases), which belong to the glycoside hydrolase 5 (GH5) family of CAZymes (Drula et al 2022) and were presumably horizontally acquired from bacteria by plant-parasitic nematodes (Smant et al 1998). Since then, numerous examples of CAZymes acquired by HGT from bacterial or fungal donors and active on polysaccharides constitutive of the plant cell wall have been described in plant-parasitic nematodes (Danchin et al 2010; Haegeman et al 2011; Danchin and Rosso 2012; Palomares-Rius et al 2014; Vicente et al 2019), but also in phytophagous arthropods (Pauchet et al 2010; Pauchet and Heckel 2013; Kirsch et al 2014; Pauchet et al 2014; Evangelista et al 2015; Antony et al 2017; Faddeeva-Vakhrusheva et al 2017; Busch et al 2019; Shin et al 2021; Le et al 2022; Shin and Pauchet 2023). HGT-acquired CAZymes identified in plant-parasitic nematodes and phytophagous arthropods also include enzymes directly involved in plant carbohydrate assimilation for energy metabolism (Acuña et al 2012; Sun et al 2013; Danchin et al 2016; Dai et al 2021).…”