Multifunctional cellulase enzymes are ancestral in Polyneoptera

Abstract

Many hemimetabolous insects produce their own cellulase enzymes from the glycoside hydrolase family 9, first observed in termites and cockroaches. Phasmatodea have multiple cellulases, some of which are multifunctional and can degrade xylan or xyloglucan. To discover when these abilities evolved, we identified cellulases from the Polyneoptera sampled by the 1000 Insect Transcriptome and Evolution (1KITE) project, including all cockroach and termite transcriptomes. We hoped to identify what role enzyme substrate specificities had in the evolution of dietary specification, such as leaf‐feeding or wood‐feeding. Putative cellulases were identified from the transcriptomes and analysed phylogenetically. All cellulases were amplified from an exemplar set of Polyneoptera species using rapid amplification of cDNA ends PCR and heterologously expressed in an insect cell line, then tested against different polysaccharides for their digestive abilities. We identified several multifunctional xyloglucanolytic enzymes across Polyneoptera, plus a large group of cellulase‐like enzymes found in nearly all insect orders with no discernible digestive ability. Multifunctional xylanolytic cellulases remain unique to Phasmatodea. The presence or absence of multifunctional enzymes does not impact dietary specification, but rather having multiple, multifunctional cellulase genes is an ancestral state for Polyneoptera and possibly Insecta. The prevalence of multifunctional cellulases in other animals demands further investigation.

Integrative omics analysis of the termite gut system adaptation to Miscanthus diet identifies lignocellulose degradation enzymes

“…Until now, hemicellulose degradation seems to be conducted by gut microbes, and no putative hemicellulolytic genes were recovered from the reconstructed termite transcriptome. For comparison, recent discovery of multi-functional GH9 cellulases in Phasmatodea suggested that some insects are capable to target xylan and xyloglucan in addition to cellulose 36 . The same study evidenced multi-functionality for two GH9 cellulases from Mastotermes darwiniensis, suggesting that some endogenous GH9 members in termites might also hydrolyse hemicellulose.…”

Analyzing the Substrate Specificity of a Class of Long‐Horned‐Beetle‐Derived Xylanases by Using Synthetic Arabinoxylan Oligo‐ and Polysaccharides

“…For example, in the bean beetle Callosobruchus maculatus , a protein from the subfamily 10 of GH5 (GH5_10)—a typical family of mannanases—has been identified; this protein accepts only xylan as a substrate . In stick and leaf insects (Phasmatodea), a gene family encoding GH9 proteins expanded through several gene duplication events, resulting in one clade of orthologous GH9 proteins having the ability to use both amorphous cellulose and xylan as substrates . We expect that more insect‐derived xylanases will be identified in the near future, due to the increasing amount of transcriptome/genome data which are currently generated, in particular for phytophagous/xylophagous species.…”

Purification and characterization of an endogenous cellulase from the digestive system of grub of banana pseudostem weevil Odoiporus longicollis (Olivier)

“…xyloglucanolytic cellulase and a speci c ancestral cellulase that lacks cellulolytic ability in almost all the insect orders necessitate the critical investigation with expansion of enzyme hypothesis (Shelomi et al, 2020). These divergent approaches to the insect cellulases indicate its multifaceted potentialities that hold a strong stand in research pursuits.…”