Sequencing and Characterization of Novel PII Signaling Protein Gene in Microalga Haematococcus pluvialis.

The PII signaling protein is a key protein for controlling nitrogen assimilatory reactions in most organisms, but little information is reported on PII proteins of green microalga . Since cells can produce a large amount of astaxanthin upon nitrogen starvation, its PII protein may represent an important factor on elevated production of astaxanthin. This study identified and isolated the coding gene (Hp) from this microalga. The full-length of Hp was 1222 bp, including 621 bp coding sequence (CDS), 103 bp 5' untranslated region (5' UTR), and 498 bp 3' untranslated region (3' UTR). The CDS could encode a protein with 206 amino acids (HpPII). Its calculated molecular weight (Mw) was 22.4 kDa and the theoretical isoelectric point was 9.53. When cells were exposed to nitrogen starvation, the Hp expression was increased 2.46 times in 48 h, concomitant with the raise of astaxanthin content. This study also used phylogenetic analysis to prove that HpPII was homogeneous to the PII proteins of other green microalgae. The results formed a fundamental basis for the future study on HpPII, for its potential physiological function in astaxanthin biosysthesis.