Chitin deacetylases (CDAs) are extracellular-modifying enzymes that deacetylate chitin to produce chitosan. In insects, this modification may contribute to the affinity and/or cross-linking of chitin/chitosan-like polysaccharides for a variety of structural proteins, which may lead to diverse mechanical properties of the cuticle. We previously reported the functional importance of Group I CDAs, TcCDA1 and TcCDA2, as well as the two alternative spliced isoforms of the latter, TcCDA2a and TcCDA2b from the red flour beetle, Tribolium castaneum in molting, morphology of cuticle and movement of legs. In this study, we further analyzed protein localization, ultrastructural defects of the cuticles and leg joints after RNAi of those genes. Both proteins are mainly present in the innermost procuticle region called the “assembly zone”. Loss of function of either TcCDA1 or TcCDA2 caused disorganized chitinous horizontal laminae and vertical pore canals in both the rigid and soft cuticles. RNAi of TcCDA2b affects cuticle integrity similar to that seen in RNAi of the two alternatively spliced forms of TcCDA2. In contrast, TcCDA2a-deficient adult, like that seen in the hypomorphic phenotype produced by RNAi of TcCDA1, exhibited ruptured tendons between femur and tibia, resulting in loss of locomotion ability. These results suggest that Group I CDAs play critical roles in molting, morphology, ultrastructure and mobility in T. castaneum.
This work was supported by NRFs (NRF-2015R1A6A3A04060323 and NRF-2018R1A2B6005106).

• Seulgi Mun(Department of Applied Biology, Chonnam National University, Korea)
• Mi Young Noh(Department of Applied Biology, Chonnam National University, Korea, Department of Forestry, Chonnam National University, Korea)
• Subbaratnam Muthukrishnan(Department of Biochemistry and Molecular Biophysics, Kansas State University, USA)
• Karl J. Kramer(Department of Biochemistry and Molecular Biophysics, Kansas State University, USA)
• Yasuyuki Arakane(Department of Applied Biology, Chonnam National University, Korea)