Chitin deacetylase: A potential target for Mythimna separata (Walker) control

Chitin deacetylase (CDA) is a hydrolytic enzyme that modifies chitin into chitosan in the body of insects. In this study, we obtained a full-length complementary DNA sequence (MsCDA1) from the oriental armyworm Mythimna separata by high-throughput sequencing. MsCDA1 is 1,952 bp long and includes 1,620 bp open reading frame encoding 539 amino acids. Analysis by quantitative real time polymerase chain reaction showed that MsCDA1 expression was higher at the adult stage than at earlier developmental stages. MsCDA1 was expressed in all larval tissues examined, in which the highest expression level was found in the midgut. The RNA interference (RNAi) suppressed MsCDA1 expression levels at 12, 24, and 48 hr after injection of double-stranded RNA (1-4 μg per larva) specific to MsCDA1. Under RNAi condition, CDA enzyme activity was significantly reduced and changes an ultramicroscopic structure of M. separata peritrophic matrix especially in its microfibrillar organization exhibiting loose network. In contrast, the surface of the peritrophic matrix was relatively smooth and well organized at control or low RNAi conditions. Moreover, RNAi of MsCDA1 expression impaired larval growth and development, occasionally leading to larval death. These results demonstrate that MsCDA1 plays a crucial role in maintaining peritrophic matrix integrity in M. separata.