Accumulation of potentially toxic elements by plants of North Caucasian Alyssum species and their molecular phylogenetic analysis.

Accumulations of potentially toxic metals were investigated in soils and five North Caucasian Alyssum species from metalliferous areas and non-metalliferous areas in Karachay-Cherkessia, Kabardino-Balkaria, Dagestan and the Krasnodar region. Analyses of field samples showed that chemical features of the soils significantly affected the concentrations of Ni, Co, Zn, but had less effect on Cu and Pb concentrations in the shoots of Alyssum. Variations in the degree of accumulating ability were found in the studied species, including hyperaccumulation of Ni in Alyssum murale (up to 12,100 mg kg-1), and significant accumulation of Zn in A. gehamense (up to 1700 mg kg-1). A comparative molecular genetic analysis of two A. murale populations, both Ni-hyperaccumulating population from Karachay-Cherkessia and non-hyperaccumulating population from Dagestan, indicated considerable genetic difference between them. This result supports the hypothesis that the selection of metal hyperaccumulator species with enhanced phytoremediation efficiency should be considered at the population level.

Role of Autophagy in Haematococcus lacustris Cell Growth under Salinity.

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.