RNA interference unveils the importance of Pseudotrichonympha grassii cellobiohydrolase , a protozoan exoglucanase, in termite cellulose degradation

Based on prior work, a cellulase from glycosyl hydrolase family 7 (GHF7) was identified and found to be expressed at a high level in Coptotermes formosanus . To determine the function of GHF7 family members in vivo , we used RNA interference (RNAi) to functionally analyse the exoglucanase gene Pseudotrichonympha grassii cellobiohydrolase gene (PgCBH) , which was highly expressed in Pseudotrichonympha grassii , a flagellate found in the hindgut of C. formosanus . In this study, the expression level of PgCBH was down‐regulated by RNAi, causing the death of P. grassii , but no effect was observed for other flagellates found in C. formosanus . RNAi also resulted in significantly reduced exoglucanase activity, and no effect was observed for endoglucanase and β‐glucosidase activities. This result demonstrated that the PgCBH gene plays a role in the protist lignocellulolytic process and is also important for host survival. PgCBH can be used as a target gene and has potential as a bioinsecticide for use against termites.