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Review
. 2019 Dec 17;8(12):1657.
doi: 10.3390/cells8121657.

Salinity Stress Responses and Adaptation Mechanisms in Eukaryotic Green Microalgae

Prateek Shetty  1 , Margaret Mukami Gitau  1 , Gergely Maróti  1   2
Affiliations
Review

Salinity Stress Responses and Adaptation Mechanisms in Eukaryotic Green Microalgae

Prateek Shetty et al. Cells. .

Abstract

High salinity is a challenging environmental stress for organisms to overcome. Unicellular photosynthetic microalgae are especially vulnerable as they have to grapple not only with ionic imbalance and osmotic stress but also with the generated reactive oxygen species (ROS) interfering with photosynthesis. This review attempts to compare and contrast mechanisms that algae, particularly the eukaryotic Chlamydomonas microalgae, exhibit in order to immediately respond to harsh conditions caused by high salinity. The review also collates adaptation mechanisms of freshwater algae strains under persistent high salt conditions. Understanding both short-term and long-term algal responses to high salinity is integral to further fundamental research in algal biology and biotechnology.

Keywords: Chlamydomonas; adaptation; green algae; high salt stress; salinity; transcriptome.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Conceptual image detailing the morphological changes that occur when normal cell (A) is exposed to saline conditions (B–G). (A) A C. reinhardtii cell under no stress, (B) Upregulation of membrane transport proteins, (C) Accumulation of osmoregulatory solutes, (D) Degradation of light harvesting complexes, (E) Palmelloid formation, (F) Flagellar loss and reduction of motility, (G) Accumulation of lipids.
Figure 2
Figure 2
Optical microscopy images of Chlamydomonas reinhardtii cc124 under normal condition (A) and under salt stressed (150 mM NaCl) condition (B) (unpublished in-house data).
Figure 3
Figure 3
Electron microscopy images of Chlamydomonas reinhardtii cc124 under normal condition (A) and under salt stressed (150 mM NaCl) condition (B) (unpublished in-house data).
Figure 4
Figure 4
Confocal microscopy images of Chlamydomonas reinhardtii cc124 under normal condition (A) and under salt stressed (150 mM NaCl) condition (B). Calcofluor white stains cellulose and chitin and is blue in color while photosystem II was excited and visualized in red. These images show an increase in polysaccharides as an integral event of the palmelloid formation (unpublished in-house data).
Figure 5
Figure 5
Schematic diagram of Glycerol and TAG synthesis. Metabolites: G1P- glucose 1-phosphate, G6P- glucose 6-phosphate, F6P- fructose 6-phosphate, FBP-, DHAP- dihydroxyacetone phosphate, GA3P- glyceraldehyde 3- phosphate, G3P- glycerol 3-phosphate, RuBP- ribulose 1,5-bisphosphate carboxylase/oxygenase, 3PGA- 3-phosphoglycerate, LPA-, PA-, DAG-, TAG-. Enzymes: AMY- α-amylase, SP- starch phosphorylase, PGM- phosphoglucomutase, PGI- phosphoglucoisomerase, GPDH- glycerol 3-phosphate dehydrogenase, GPAT- glycerol-3-phosphate acyltransferase, LPAAT- lysophosphatidic acid acyltransferase, PAP- phosphatidate phosphatase, DGAT- Diacylglycerol acyltransferase, MCAT- Malonyl CoA-acyl carrier protein transacylase, ACCase- AcCoA carboxylase, PDH- pyruvate dehydrogenase, PFOR- pyruvate-ferredoxin oxidoreductase, GK- glycerol kinase, GPP- glycerol-3-phosphate phosphatase. Others: Free FA- free fatty acids, Co-A- Coenzyme A.
See this image and copyright information in PMC

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