Tolerance of soil algae and cyanobacteria to drought stress

Abstract

Tolerance to drought stress in soil crust microorganisms is essential for exploiting suitable organisms for restoring soil. In this study, the responses to drought stress of two drought-tolerant species, a green alga and a cyanobacterium, were compared with those of two non-tolerant green algae. In response to drought stress, induced by treatment with polyethylene glycol, the intracellular proline levels increased and were associated with increases in malondialdehye, pigment contents, and enzyme activities such as superoxide dismutase (SOD) and peroxidase (POD). Our results suggest that tolerance to drought stress could be indicated by the intracellular levels of proline, SOD, and carotenoids. This study provides insights into the drought physiology of the photosynthetic microorganisms and suggests that Leptolyngbya boryana and Chlorella vulgaris are suitable pioneer organisms for soil restoration.

Stress responses of the green microalga, Dunaliella salina to PEG-induced drought

“…According to our results, D. salina indicated a high ability to accumulate more intracellular proline contents in response to drought stress, which was highly correlated with the increased doses of PEG. This was compatible with the results of Delauney et al (1993) and Molinari et al (2007) for higher plants and Lin & Wu (2014) for soil algae and cyanobacteria. In the current study, it was also found that the proline accumulation co-occurred with a significant PEG-induced H 2 O 2 generation, especially in 5% PEG-treated cells.…”

“…Although there are numerous reports focused on the defence mechanisms in response to drought stress in higher plants and some species of algae (Gechev et al ., 2013; Lin & Wu, 2014), to the best of our knowledge, there has been no study about physiological responses of the microalga Dunaliella to drought stress to date. Recently, Lee & Yeh (2014) evaluated the effects of PEG concentrations on cell growth, size variation and lipid production of microalgae, Nannochloropsis oculata .…”

“…In the present study, PEG concentrations of more than 5% induced significant mortality rates and finally quickly reaching a plateau phase. Lin & Wu (2014) stated that the total inhibition in the growth of Chlorella vulgaris did not take place even at PEG concentrations of more than 40%. Other microalgae in the same study, including Chlamydomonas reinhardtii , Klebsormidium flaccidum and Leptolyngbya boryana , also continued to grow in PEG-6000 concentrations by more than 20%, 30% and 40%, respectively.…”

“…In response to various stresses such as salt stress, drought stress, cold stress, heavy metal toxicity and UV or gamma radiation, cells tend to accumulate a considerable amount of compatible solutes like low-molecular-weight compounds such as proline, glycine betaine and glycerol as well as other kinds of sugars. Solutes accumulation is well known to be a species-dependent character, such that the resistant plants generally produce larger amounts of compatible compounds in response to stresses (Delauney et al ., 1993; Molinari et al ., 2007; Lin & Wu, 2014; Toghyani et al ., 2020). The compatible solutes could help osmotic and volume control and act as an osmoprotectant (Molinari et al ., 2007), a redox buffer (Hare & Cress, 1997), protecting enzymes and proteins against destruction (Matysik et al ., 2002), a regulator of cytosolic acidity (Venekemp, 1989), a remover of free radicals (Matysik et al ., 2002) and a membrane stabilizer (Lin & Wu, 2014).…”

“…For instance, Holzinger & Karsten (2013) have reviewed the mechanisms of desiccation tolerance in green algae at the ultra-structural, physiological and molecular levels. More recently, Lin & Wu (2014) compared the PEG-induced drought responses of some drought-tolerant and non-tolerant algal species and suggested that the tolerance to drought stress might be indicated by physiological parameters such as the proline level and the enzymatic and non-enzymatic antioxidant system.…”