Expression patterns of ubiquitin, heat shock protein 70, α-actin and β-actin over the molt cycle in the abdominal muscle of marine shrimp Litopenaeus vannamei

Crustacean muscle growth is discontinuous due to molt cycle. To characterize molt-related gene expression patterns, we studied the mRNA levels of molecular chaperone-ubiquitin and heat shock protein 70 (Hsp 70) in comparison with muscle protein a-actin and P-actin in marine shrimp Litopenaeus vannamei. Total RNA from abdominal muscle was isolated from 3-month-old animals in six different molt stages. The mRNA levels of target genes were detected by reverse-transcriptase-multiplex PCR and expressed as the ratio to elongation factor-la. Ubiquitin mRNA levels were relatively steady over all stages of the molt cycle. Hsp70 levels were not detectable in early postmolt and late premolt stages, but showed a progressive increase from late postmolt to intermolt stages. Expression levels of a-actin gene were lower during postmolt, reached a plateau in intermolt and remained relatively high in premolt stage, Levels of P-actin increased progressively from postmolt to intermolt, reaching a maximum value in premolt. Therefore, the mRNAs encoding for ubiquitin and Hsp 70 in abdominal muscle did not increase significantly in premolt stages, which is typically associated with claw muscle degradation. Muscle structural a-actin and cytoskeletal P-actin were increased during intermolt and premolt stages, suggesting high muscle growth during these stages in the abdominal muscle of the L. vannamei.