The microalga Haematococcus lacustris (formerly H. pluvialis) is able to accumulate high amounts of the carotenoid astaxanthin in the course of adaptation to stresses like salinity. Technologies aimed at production of natural astaxanthin for commercial purposes often involve salinity stress; however, after a switch to stressful conditions, H. lacustris experiences massive cell death which negatively influences astaxanthin yield. This study addressed the possibility to improve cell survival in H. lacustris subjected to salinity via manipulation of the levels of autophagy using AZD8055, a known inhibitor of TOR kinase previously shown to accelerate autophagy in several microalgae. Addition of NaCl in concentrations of 0.2% or 0.8% to the growth medium induced formation of autophagosomes in H. lacustris, while simultaneous addition of AZD8055 up to a final concentration of 0.2 µM further stimulated this process. AZD8055 significantly improved the yield of H. lacustris cells after 5 days of exposure to 0.2% NaCl. Strikingly, this occurred by acceleration of cell growth, and not by acceleration of aplanospore formation. The level of astaxanthin synthesis was not affected by AZD8055. However, cytological data suggested a role of autophagosomes, lysosomes and Golgi cisternae in cell remodeling during high salt stress.

The study was focused on effects of increased zinc concentrations on growth, mineral composition, chlorophyll and carotenoid content in Sisymbrium lipskyi N. Busch from North Caucasus. Plants were cultivated in sand in presence of 80, 160 and 320 mg Zn per kg of substrate. S. lipskyi demonstrated relatively high resistance to zinc toxicity at doses of 80 and 160 mg/kg – plants showed no significant decrease in dry biomass accumulation, no significant changes in chlorophyll a/b ratio, and water status was consistent. A significant inhibitory effect of zinc was observed only at its concentration of 320 mg/kg and resulted in significant decrease in biomass and chlorophyll b content. The balance of mineral elements was disturbed, mainly due to decrease in mineral elements translocation from roots to above-ground organs of plants. The predominant accumulation of zinc in roots (except for the 320 mg/kg treatment) defines S. lipskyi as a species capable of restricting zinc supply to above-ground organs, as evidenced by low values of translocation factor. This feature of mineral metabolism, along with relatively high tolerance to zinc, suggests to consider S. lipskyi as a promising species for phytostabilization of relatively polluted soils.

Устойчивость растений Sisymbrium lipskyi к цинку и их фиторемедиационный потенциал Устойчивость растений Sisymbrium lipskyi к цинку и их фиторемедиационный потенциал