Physiological and transcriptome analysis elucidates the metabolic mechanism of versatile Porphyridium purpureum under nitrogen deprivation for exopolysaccharides accumulation

Abstract

Porphyridium purpureum is a mesophilic, unicellular red alga rich in phycoerythrin, sulfate polysaccharides, and polyunsaturated fatty acids. Nitrogen deficiency inhibited the growth of P. purpureum and resulted in yellowing of the cells and thickening of the extracellular viscousness sheath. Under nitrogen stress, the contents of total lipids and exopolysaccharides in P. purpureum were increased by 65.2% and 188.0%, respectively. We demonstrate that the immediate response of P. purpureum to nitrogen deficiency is mediated by carbon flow to polysaccharide synthesis, while the synthesis of lipids is enhanced as a permanent energy storage substance at the later stage. Based on transcriptome annotation information, we elucidate the synthesis pathway of polysaccharides from P. purpureum from the perspective of glycosyl-donor interconversion, and demonstrate that the n-6 pathway is the main synthesis pathway of polyunsaturated fatty acids. This study not only provides a production strategy for polysaccharides and fatty acids by single-celled marine red algae P. purpureum, but also provides targets for further genetic modification.

Maximizing Polysaccharides and Phycoerythrin in Porphyridium purpureum via the Addition of Exogenous Compounds: A Response-Surface-Methodology Approach

“…In addition to influencing the growth of P. purpureum , the nitrogen source can also affect the synthesis of phycoerythrin. Nitrogen deficiency has been previously observed to decrease the content and stability of phycobilisomes associated with photosynthetic activity in P. purpureum [ 39 ]. It has also been reported that the maximum phycoerythrin concentration in P. purpureum UTEX LB 2757 occurred at a low nitrogen concentration of 0.075 g L −1 [ 17 ].…”

Cell adaptation of the extremophilic red microalga Galdieria sulphuraria to the availability of carbon sources

“…Overall, these results suggest that some of the gene families acquired by HGT are subject to transcriptional regulation in G. sulphuraria . Whether this transcriptional regulation is specific to this alga or common amongst the red algae with HGT still needs to be deciphered ( Ji et al, 2021 ).…”

Circadian rhythm promotes the biomass and amylose hyperaccumulation by mixotrophic cultivation of marine microalga Platymonas helgolandica

“…Cells from day 9 were collected for transmission electron microscopy (TEM). Cell pretreatment and section preparation were performed according to standard procedures [ 40 ]. Cutall microtome LEICA EM UC7 was used to prepare samples.…”