THE FUNCTION AND MECHANISM OF BURSICON GENE IN CARIDINA

To study the function of bursicon gene in Caridina during molting and cuticle formation, its open reading frame (ORF) containing two subunits genes were amplified by PCR respectively. The ORF of bursicon-α is 441 bp in length, encoding a protein with 146 amino acid residues. The ORF of bursicon-β is 411 bp in length, encoding a protein with 136 amino acid residues. The dynamic changes in the expression of both bursicon subunit genes during the molt cycle in Caridina have been analyzed by the real-time quantitative PCR. Relative expression of both bursicon-α and bursicon-β had different levels in different stages of the molt cycle, which increased through premolt stage (D stage) and reached their peak level at the D₃ stage. The mRNA accumulation decreased to its lowest level at the molt stage (E stage). RNA interference-mediated knockdown of bursicon-α and bursicon-β retard the molting process and ecdysis behavior of Caridina. The cuticle of dsRNA-treated Caridina was thinner than that in the control group. These findings demonstrate that bursicon is involved in the thickening and hardening of cuticle in newly formed exoskeleton. Moreover, bursicon plays an important role in molt cycle.