Exogenous Abscisic Acid Confers Salinity Tolerance in Chlamydomonas reinhardtii During Its Life Cycle

Abstract

The plant hormone abscisic acid (ABA) coordinates responses to environmental signals with developmental changes and is important for stress resilience and crop yield. However, fundamental questions remain about how this phytohormone affects microalgal growth and stress regulation throughout the different stages of their life cycle. In this study, the effects of ABA on the physiology of the freshwater microalga Chlamydomonas reinhardtii at its different life cycle stages were investigated. Exogenously added ABA enhanced the growth and photosynthesis of C. reinhardtii during the vegetative stage. The hormone also increased the tolerance of this alga to high‐salinity stress during gamete formation under nutrient depletion, as well as it extended their survival. We show that the level of reactive oxygen species (ROS) generated in the ABA‐treated cells was significantly less than that in the untreated cells under inhibiting NaCl concentrations. Cell size examination showed that ABA prevents cells from forming palmella when exposed to high salinity. All together, these results suggest that ABA can support the vitality and survival of C. reinhardtii under high salt conditions.

Genome-Wide Analysis of the WRKY Gene Family in Malus domestica and the Role of MdWRKY70L in Response to Drought and Salt Stresses

“…Taken together, we demonstrated that MdWRKY70L improved the drought and salt stress tolerance in plants. Exogenous ABA improves salt stress tolerance in Lonicera lonicera and drought stress tolerance in Gynura cusimbua [ 56 , 57 ]. Studies have demonstrated that ABA-induced WRKY gene expression is often related to drought and salt stress [ 15 , 58 , 59 ].…”

Plant Growth Promotion, Phytohormone Production and Genomics of the Rhizosphere-Associated Microalga, Micractinium rhizosphaerae sp. nov.

“…In plants, ABA plays essential roles in multiple physiological processes as well as in responses to abiotic and biotic stresses [ 42 ]. In microalgae, the production of ABA is also related to the presence of stress conditions and is thought to also be involved in the regulation of microalgae growth and [ 41 , 43 ]. The exogenous application of ABA also leads to the accumulation of lipids in Chlorella [ 39 , 44 ].…”

Chlamydomonas Responses to Salinity Stress and Possible Biotechnological Exploitation

“…Studies suggested that the phytormone abscissic acid (ABA) can support C. reinhardtii survival under high salt conditions. In fact, externally added ABA successfully reduced the deleterious effects of salt stress-induced oxidative stress, partially releasing the growth suppression and reducing ROS generation under salinities around 100 mM of NaCl [37,38]. In a recent study, ABA addition also fully recovered photosynthesis and prevented palmelloid formation under moderately high NaCl levels, whereas it supported the growth of C. reinhardtii at their gamete phase [38].…”

“…In fact, externally added ABA successfully reduced the deleterious effects of salt stress-induced oxidative stress, partially releasing the growth suppression and reducing ROS generation under salinities around 100 mM of NaCl [37,38]. In a recent study, ABA addition also fully recovered photosynthesis and prevented palmelloid formation under moderately high NaCl levels, whereas it supported the growth of C. reinhardtii at their gamete phase [38]. Thus, Chlamydomonas do respond to ABA even though there are no evidence suggesting it is internally synthesized, and ABA protects Chlamydomonas cells from high salinity, possibly as a signal molecule that mitigates the oxidative stress derived from these conditions.…”