Abstract
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 Haematococcus pluvialis. Since H. pluvialis cells can produce a large amount of astaxanthin upon nitrogen starvation, its PII protein may represent an important factor on elevated production of Haematococcus astaxanthin. This study identified and isolated the coding gene (HpGLB1) from this microalga. The full-length of HpGLB1 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 H. pluvialis cells were exposed to nitrogen starvation, the HpGLB1 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 Haematococcus astaxanthin biosysthesis.
Highlights
Inorganic nitrogen acts as an important nutrient in autotrophic microalgae cultivation
A 148 bp cDNA fragment of HpGLB1 was obtained from H. pluvialis cells by RT-PCR in this study
A 148 bp cDNA fragment of HpGLB1 was obtained from H. pluvialis cells by RT‐PCR in this
Summary
Inorganic nitrogen acts as an important nutrient in autotrophic microalgae cultivation. It is a limiting factor for cell growth. While under a nitrogen-depleted condition, microalgae will transfer the energy from cell division/growth to produce more secondary metabolites like carotenoids [1,2] and lipids [3], which have widespread commercial value. Nitrogen regulation is an important approach for microalgae cultivation. It is believed that nitrogen metabolism is regulated by multiple signal regulators and linked to carbon flux [4]. PII proteins act as the central signal-integrating molecules for controlling nitrogen and/or carbon metabolism, along with some effector molecules
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