Heat stress response in the closest algal relatives of land plants reveals conserved stress signaling circuits.

All land plants (embryophytes) share a common ancestor that likely evolved from a filamentous freshwater alga. Elucidating the transition from algae to embryophytes - and the eventual conquering of Earth's surface - is one of the most fundamental questions in plant evolutionary biology. Here, we investigated one of the organismal properties that might have enabled this transition: resistance to drastic temperature shifts. We explored the effect of heat stress in Mougeotia and Spirogyra, two representatives of Zygnematophyceae - the closest known algal sister lineage to land plants. Heat stress induced pronounced phenotypic alterations in their plastids, and high-performance liquid chromatography-tandem mass spectroscopy-based profiling of 565 transitions for the analysis of main central metabolites revealed significant shifts in 43 compounds. We also analyzed the global differential gene expression responses triggered by heat, generating 92.8 Gbp of sequence data and assembling a combined set of 8905 well-expressed genes. Each organism had its own distinct gene expression profile; less than one-half of their shared genes showed concordant gene expression trends. We nevertheless detected common signature responses to heat such as elevated transcript levels for molecular chaperones, thylakoid components, and - corroborating our metabolomic data - amino acid metabolism. We also uncovered the heat-stress responsiveness of genes for phosphorelay-based signal transduction that links environmental cues, calcium signatures and plastid biology. Our data allow us to infer the molecular heat stress response that the earliest land plants might have used when facing the rapidly shifting temperature conditions of the terrestrial habitat.

Toxic potential of iron oxide, CdS/Ag2S composite, CdS and Ag2S NPs on a fresh water alga Mougeotia sp.

Nanoparticles (NPs) are being used in many industries ranging from medical, textile, automobile, consumer products, etc. This may increase the probability of their (NPs) release into the environment and fresh water ecosystems. The present study focuses on testing the potential effect of iron oxide, nanocomposite of cadmium sulfide and silver sulfide, cadmium sulfide and silver sulfide nanoparticles (NPs) on a fresh water alga Mougeotia sp. as the model organism. The alga was treated with different concentrations of NPs (0.1-25 mg/L). The NPs exposure caused lipid peroxidation and ROS production, and suppressed the antioxidant defense system such as catalase, glutathione reductase, and superoxide dismutase. Adsorption of NPs on algal surface and membrane damage were confirmed through microscopic evaluation and increase in protein content in extracellular medium. The present investigation pointed out the ecological implications of NPs. The study warrants the need for regulatory agencies to monitor and regulate the use of NPs.