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

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.

From cyanobacteria to Archaeplastida: new evolutionary insights into PII signalling in the plant kingdom

“…5). This result suggested that PII may play a role in regulating astaxanthin biosynthesis (Ma et al, 2017). Nonetheless, PII targets in H. pluvialis must first be elucidated before any conclusion about PII function can be made.…”

“…In addition to N starvation and the effects of inorganic N (Ermilova et al, 2013;Ma et al, 2017;Zalutskaya et al, 2018), PII may be regulated by organic N. For instance, in P. parva, Arg supports the growth of this nonphotosynthetic alga and influences PII abundance, with high internal Arg concentrations corresponding to high PII levels (Lapina et al, 2019). However, the exact mechanism by which external Arg regulates PII levels awaits further studies.…”

Astaxanthin accumulation in the green microalga Haematococcus pluvialis: Effect of initial phosphate concentration and stepwise/continuous light stress

“…Furthermore, phosphorous is crucial in the transfer of energy within cells, membrane development and biosynthesis of nucleic acids and phospholipids [ 45 ]. Thus, limited availability of phosphorous in the growth media would adversely affect cell growth, and energy otherwise used in cell division would be transferred to carotenogenesis [ 24 , [46] , [47] , [48] ]. Nonetheless, numerous studies have reported that high phosphate concentrations could also inhibit the growth of microalgae due to the phenomenon identified as phosphorus toxicity, as further evinced by results of the present study [ 49 , 50 ].…”

Dual positive and negative control of Chlamydomonas PII signal transduction protein expression by nitrate/nitrite and NO via the components of nitric oxide cycle

“…Importantly, no homologues of PipX and NtcA are conserved in plants [ 12 ]. In representative plants, PII proteins are regulated at the transcriptional level [ 20 – 22 ]. In this study, we demonstrate that expression of Chlamydomonas PII is under the complex control of positive signals (i.e., nitrate and nitrite) and negative signals (NO), and GLB1 gene expression pattern is very similar to that observed for nitrate assimilation genes.…”

“…In Chloroplastida (green algae and land plants) PII-encoding GLB1 genes are nuclear-encoded and, in Rhodophyta they are coded by the plastid genome [ 6 ]. It is believed that regulation of PII in plants may be transcriptional [ 20 – 22 ]. However, unlike bacteria, the transcriptional control of plant PII expression remains poorly understood.…”