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.

This paper describes a new species from the class Chlorophyceae, Heterochlamydomonas uralensis sp. nov., isolated from the soil of the carex-moss-lichen tundra in the Subpolar Urals Mountains, Russia. The taxon is studied using morphological methods and DNA identification. Heterochlamydomonas uralensis differs from other Heterochlamydomonas spp. by cellular morphology, detected on light and ultrastructural levels, and 18S and ITS2 rDNA sequences. These results support the separation of the species Heterochlamydomonas uralensis sp. nov. This study is important for connecting data from DNA metabarcoding with species described on the basis of morphological characteristics.

This first inventory of the charophytes of the Caucasus region was compiled based on records from published references, online sources, a review of herbarium collections, and our own field collections. The documented Caucasian charophyte flora includes 27 species from six genera: 18 Chara species, 6 Nitella, 2 Tolypella, and 1 species each of Lamprothamnium, Nitellopsis, and Sphaerochara. Chara uzbekistanica, C. virgata, and C. contraria var. hispidula are newly recorded for the Caucasus. The high species richness of the genus Chara, the much less diverse genus Nitella, and a few species of Tolypella and Sphaerochara in the Caucasian charophyte flora are typical traits of Palearctic charophyte floras. In total, there are 10 species recorded in Armenia, 16 in Azerbaijan, 18 in Georgia, and 16 in the mountainous region of the North Caucasian Federal District of Russia. Most of the species have wide distributions; none are endemic to the Caucasus. One of the most commonly recorded species in the region, C. gymnophylla, is a usual feature of the Mediterranean and West Asia. The Caucasian charophyte flora can be described as unsurprising from a large-scale perspective, considering its species distribution ranges. However, the association of species makes the region specific at the scale of West Asia when comparing it to its large neighboring areas.

Filamentous green chaetophoralean algae are distributed mainly in aquatic ecosystems, less known from terrestrial habitats. Many of them have a complicated thalli and complex life cycles that make it difficult to determine these organisms by morphology. Description of new representatives of the Chaetophorales continues. In this study, we have explored the filamentous green alga IRK–A 341 from soil of the Baikal Region by light and electron microscopy along with molecular phylogeny. Based on the results of morphological, ecological, and molecular phylogenetic analyses (18S–28S rDNA, tufA), we described the studied alga as the new species, Barranca variabilis sp. nov. The study complements the data on the diversity of soils green filamentous algae, and their biogeography. For the first time, the data on the structure of the cell walls and the cell ultrastructure of Barranca were established. The information on the morphology of the reproductive and resting cells is updated.