Dataset Information

Chloromonas nivalis subsp. tatrae, subsp. nov. (Chlamydomonadales, Chlorophyta): re-examination of a snow alga from the High Tatra Mountains (Slovakia).

ABSTRACT: Melting snow fields populated by aplanozygotes of the genus Chloromonas (Chlamydomonadales, Chlorophyta) are found in polar and alpine habitats. In the High Tatra Mountains (Slovakia), cells causing blooms of brownish-red snow designated as Scotiella tatrae kol turned out to be genetically (18S, ITS1 and ITS2 rDNA, rbcL) very closely related to Chloromonas nivalis (Chodat) Hoham et Mullet from the Austrian Alps. Therefore, Sc. tatrae is transferred into the latter taxon and reduced to a subspecies as Cr. nivalis subsp. tatrae. Both exhibit a similar photosynthetic performance, thrive in similar habitats at open sites above timberline, but differ in astaxanthin accumulation and number of aplanozygote cell wall flanges. In a field sample of Cr. nivalis subsp. tatrae, polyunsaturated fatty acids formed nearly 50 % of total lipids, dominating in phospholipids and glycolipids. Cr. nivalis subsp. tatrae represents likely a variation of a common cryoflora species with distinct morphology.

SUBMITTER: Prochazkova L

PROVIDER: S-EPMC6456015 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Chloromonas nivalis subsp. tatrae, subsp. nov. (Chlamydomonadales, Chlorophyta): re-examination of a snow alga from the High Tatra Mountains (Slovakia).

Procházková Lenka L Remias Daniel D Řezanka Tomáš T Nedbalová Linda L

Fottea (Praha) 20170926 1

Melting snow fields populated by aplanozygotes of the genus Chloromonas (Chlamydomonadales, Chlorophyta) are found in polar and alpine habitats. In the High Tatra Mountains (Slovakia), cells causing blooms of brownish-red snow designated as Scotiella tatrae kol turned out to be genetically (18S, ITS1 and ITS2 rDNA, rbcL) very closely related to Chloromonas nivalis (Chodat) Hoham et Mullet from the Austrian Alps. Therefore, Sc. tatrae is transferred into the lat ...[more]

PMID: 30976329

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Project description:Cold environments, such as glaciers and alpine regions, constitute unique habitats for organisms living on Earth. In these harsh ecosystems, snow algae survive, florish, and even become primary producers for microbial communities. How the snow algae maintain physiological activity during violent ambient temperature changes remains unsolved. To explore the cold adaptation mechanisms of the unicellular snow alga Chlamydomonas nivalis, we compared its physiological responses to a model organism from the same genus, Chlamydomonas reinhardtii. When both cell types were exposed to a shift from 22°C to 4°C, C. nivalis exhibited an apparent advantage in cold tolerance over C. reinhardtii, as C. nivalis had both a higher growth rate and photosynthetic efficiency. To determine the cold tolerance mechanisms of C. nivalis, RNA sequencing was used to compare transcriptomes of both species after 1 h of cold treatment, mimicking temperature fluctuations in the polar region. Differential expression analysis showed that C. nivalis had fewer transcriptomic changes and was more stable during rapid temperature decrease relative to C. reinhardtii, especially for the expression of photosynthesis related genes. Additionally, we found that transcription in C. nivalis was precisely regulated by the cold response network, consisting of at least 12 transcription factors and 3 RNA-binding proteins. Moreover, genes participating in nitrogen metabolism, the pentose phosphate pathway, and polysaccharide biosynthesis were upregulated, indicating that increasing resource assimilation and remodeling of metabolisms were critical for cold adaptation in C. nivalis. Furthermore, we identified horizontally transferred genes differentially expressed in C. nivalis, which are critical for cold adaptation in other psychrophiles. Our results reveal that C. nivalis adapts rapid temperature decrease by efficiently regulating transcription of specific genes to optimize resource assimilation and metabolic pathways, providing critical insights into how snow algae survive and propagate in cold environments.

Project description:Melting mountainous snowfields are populated by extremophilic microorganisms. An alga causing orange snow above timberline in the High Tatra Mountains (Poland) was characterised using multiple methods examining its ultrastructure, genetics, life cycle, photosynthesis and ecophysiology. Based on light and electron microscopy and ITS2 rDNA, the species was identified as Chloromonas krienitzii (Chlorophyceae). Recently, the taxon was described from Japan. However, cellular adaptations to its harsh environment and details about the life cycle were so far unknown. In this study, the snow surface population consisted of egg-shaped cysts containing large numbers of lipid bodies filled presumably with the secondary carotenoid astaxanthin. The outer, spiked cell wall was shed during cell maturation. Before this developmental step, the cysts resembled a different snow alga, Chloromonas brevispina. The remaining, long-lasting smooth cell wall showed a striking UV-induced blue autofluorescence, indicating the presence of short wavelengths absorbing, protective compounds, potentially sporopollenin containing polyphenolic components. Applying a chlorophyll fluorescence assay on intact cells, a significant UV-A and UV-B screening capability of about 30 and 50%, respectively, was measured. Moreover, intracellular secondary carotenoids were responsible for a reduction of blue-green light absorbed by chloroplasts by about 50%. These results revealed the high capacity of cysts to reduce the impact of harmful UV and high visible irradiation to the chloroplast and nucleus when exposed at alpine snow surfaces during melting. Consistently, the observed photosynthetic performance of photosystem II (evaluated by fluorometry) showed no decline up to 2100 μmol photons m-2 s-1. Cysts accumulated high contents of polyunsaturated fatty acids (about 60% of fatty acids), which are advantageous at low temperatures. In the course of this study, C. krienitzii was found also in Slovakia, Italy, Greece and the United States, indicating a widespread distribution in the Northern Hemisphere.

Dataset Information

Chloromonas nivalis subsp. tatrae, subsp. nov. (Chlamydomonadales, Chlorophyta): re-examination of a snow alga from the High Tatra Mountains (Slovakia).

Publications

<i>Chloromonas nivalis</i> subsp. <i>tatrae</i>, subsp. nov. (Chlamydomonadales, Chlorophyta): re-examination of a snow alga from the High Tatra Mountains (Slovakia).

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