Chlamydomonas Responses to Salinity Stress and Possible Biotechnological Exploitation

Abstract

Salinity is among the main drivers affecting growth and distribution of photosynthetic organisms as Chlamydomonas spp. These species can live in multiple environments, including polar regions, and have been frequently studied for their adaptation to live at different salinity gradients. Upon salinity stress (hypersalinity is the most studied), Chlamydomonas spp. were found to alter their metabolism, reduce biomass production (growth), chlorophyll content, photosynthetic activity, and simultaneously increasing radical oxygen species production as well as lipid and carotenoid contents. This review summarizes the current literature on salt stress related studies on the green algae from the genus Chlamydomonas considering physiological and molecular aspects. The overall picture emerging from the data suggests the existence of common features of the genus in response to salinity stress, as well as some differences peculiar to single Chlamydomonas species. These differences were probably linked to the different morphological characteristics of the studied algae (e.g., with or without cell wall) or different sampling locations and adaptations. On the other hand, molecular data suggest the presence of common reactions, key genes, and metabolic pathways that can be used as biomarkers of salt stress in Chlamydomonas spp., with implications for future physiological and biotechnological studies on microalgae and plants.

Strain-specific transcriptional responses overshadow salinity effects in a marine diatom sampled along the Baltic Sea salinity cline

“…Our data suggest that S. marinoi adopts a similar response to low salinity. Given that major salinity stress in algae usually results in a decreased chlorophyll content [ 66 ] and less photosynthesis [ 67 ], our data indicate that although low salinities are not optimal for S. marinoi , when acclimated the diatom is not severely stressed in these conditions. Furthermore, this observation might have important consequences for similar experiments that use chlorophyll a as a proxy for growth.…”

Effect of salinity on the biochemical characteristics and antioxidant activity of exopolysaccharide of Porphyridium purpureum FACHB 806

“…The tolerance mechanism of salinity stress varies among microalgae. Some microalgae could change the concentration of the intracellular metabolite to improve salinity tolerance (Bazzani et al, 2021). Microalgal EPS, which was usually wrapped around the algal cells, could provide a stable microenvironment and a natural barrier to protect the cells from the unfavorable environment (Rossi and De Philippis, 2015).…”

“…Salinity is one of the important environmental factors affecting the growth of marine microalgae (Bazzani et al, 2021). Salinity stress leads to a series of physiological and biochemical responses such as photosynthesis inhibition, secondary metabolites synthesis and osmoregulation (Lu et al, 2006).…”

Comprehensive Time-Course Transcriptome and Co-expression Network Analyses Identify Salt Stress Responding Mechanisms in Chlamydomonas reinhardtii Strain GY-D55

“…In the study published by Ji et al (2018) , the total lipid content in C. reinhardtii cells is significantly increased when exposed to salt stress (150 mM) for 48 h. Besides, 200 mM NaCl treatment inhibits the growth and significantly increases the lipid content of C. reinhardtii at 3 days (72 h) ( Hang et al, 2020 ). Salt treatment strikingly induces the production of nitric oxide (NO) after 1–3 days (24–72 h), suggesting that NO, as another second messenger, triggers salt stress response ( Chen et al, 2016 ; Bazzani et al, 2021 ). Besides, the salt stress gradually induced the activities of antioxidant enzymes after 1 or 3 days (72 h) of salt treatment, and such induced activities were declined after 3 days (72–96 h) of salt treatment.…”