Cloning and characterization of the first actin gene in Chinese oak silkworm, Antheraea pernyi

The first actin gene in Chinese oak silkworm, Antheraea pernyi (Apactin) was cloned and characterized. Remarkably, two types of the Apactin cDNA clones were isolated from the pupal cDNA library, which differed by the length and sequence of 5' untranslated region (UTR). The open reading frame (ORF) of the Apactin gene is 1131 bp and encodes a protein of 376 amino acids with a predicted molecular weight of 40.81 kDa and an isolectric point of 5.30. The deduced amino acid sequence of the Apactin gene contains typical structural features of the actin genes. Sequence alignment and phylogenetic analysis showed that the Apactin gene was a cytoplasmic actin gene and had closest genetic relationship with Antheraea yamamai actin gene. The Apactin gene held the highest identity with the Bombyx mori actin A4 gene among the four known B. mori actin isoforms. RT-PCR analysis showed that the Apactin gene was constitutively expressed during four developmental stages and in all tested tissues. These results indicate that the Apactin gene presented here plays an essential role throughout the entire life cycle and can be used as a reference gene in the normalization of gene expression.