The effect of Vibrio alginolyticus infection on caspase-3 expression and activity in white shrimp Litopenaeus vannamei.

Complementary (c)DNA encoding cysteine aspartate protease-3 (caspase-3) messenger (m)RNA of the white shrimp Litopenaeus vannamei was obtained from haemocytes by a reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) using oligonucleotide primers based on the caspase sequences of Penaeus merguiensis, Spodoptera frugiperda, Spodoptera littoralis, and Penaeus monodon. The 1212-bp cDNA contained an open reading frame (ORF) of 951bp, a 56-bp 5'-untranslated region (UTR), and a 205-bp 3'-UTR containing the poly(A) tail. The molecular mass of the deduced amino acid (aa) sequence (316aa) was 28.7kDa with an estimated pI of 6.46. It contains two hits in the caspase family, including a p20 domain profile and p10 domain profile. From aa residues 183 to 194, there was a single pattern hit for QACRG, a caspase family cysteine active site. Caspase-3 mRNA was widely distributed in all tissues; especially in haemocytes and lymphoid organ, but was weakly expressed in muscles, ganglia, spermaries, and ovaries. Shrimp injected with Vibrio alginolyticus induced transcription of caspase-3 mRNA and increased caspase-3 activity which contributed to the occurrence of apoptosis and DNA fragmentation in haemocytes.