Effect of nitrogen and temperature on the transcription of an ACAT gene in Isochrysis galbana.

Thiolases are functionally divided into two groups: 3-ketoacyl-CoA thiolase and acetoacetyl-CoA thiolase (ACAT). Acetoacetyl-CoA thiolase plays a key role in the mevalonate pathway. In this study, a novel gene, IgACAT, which encodes ACAT was cloned from Isochrysis galbana and characterized. The cDNA of IgACAT was 1551 bp in length, consisting of an open reading frame of 1173 bp, a 5' untranslated region of 69 bp and a 3' untranslated region of 309 bp. The deduced amino acid sequence of IgACAT was 390 amino acid residues in length with a predicted molecular weight of 53.59 kDa and an isoelectric point of pH 9.04. The triterpenes content and the expression of IgACAT under nitrogen and temperature stress were analyzed. When I. galbana was treated with excessive nitrogen and at 35 °C, respectively, both the triterpenes content and the abundance of IgACAT gene transcript increased. Our findings will facilitate the regulation of gene expression and genetic modification of the triterpenes synthesis pathway of I. galbana.