cDNA Cloning and Expression Analysis of Troponin C from Gryllus bimaculatus (Orthoptera: Gryllidae)

Few reports have described the effect of starvation on insect muscle physiology and development. This study examined the role of troponin C (TnC) in the skeletal muscles and digestive tracts of the two-spotted cricket (Gryllus bimaculatus; Orthoptera: Gryllidae) during starvation and re-feeding. The TnC gene of G. bimaculatus (GrybiTnC) was cloned and found to encode a 153-amino-acid protein with a theoretical isoelectric point of 4.02 and molecular weight of 17,368.23 Da. Homology analyses revealed that GrybiTnC exhibited high amino acid similarities with TnCs from other insects, showing sequence identities ranging from similar to 54 to 75%. GrybiTnC has two Ca2+-binding sites and five EF-hand motifs, similar to most TnC proteins. GrybiTnC gene expression was examined under starvation and re-feeding conditions in three different skeletal muscle and digestive tract regions. During starvation, GrybiTnC gene expression was unchanged in muscle but upregulated in the foregut and hindgut. Whereas GrybiTnC gene expression in muscle was similar under re-feeding and starvation conditions, it was upregulated in the foregut and midgut by re-feeding with carbohydrates and lipids and downregulated in the hindgut by re-feeding with carbohydrates, proteins and lipids.