Influence of fuel oil on Platymonas helgolandica: An acute toxicity evaluation to amino acids

Toxic mechanisms of the antiviral drug arbidol on microalgae in algal bloom water at transcriptomic level

Increasing antivirals in surface water caused by their excessive consumption pose serious threats to aquatic organisms. Our recent research found that the input of antiviral drug arbidol to algal bloom water can induce acute toxicity to the growth and metabolism of Microcystis aeruginosa, resulting in growth inhibition, as well as decrease in chlorophyll and ATP contents. However, the toxic mechanisms involved remained obscure, which were further investigated through transcriptomic analysis in this study. The results indicated that 885-1248 genes in algae were differentially expressed after exposure to 0.01-10.0 mg/L of arbidol, with the majority being down-regulated. Analysis of commonly down-regulated genes found that the cellular response to oxidative stress and damaged DNA bonding were affected, implying that the stress defense system and DNA repair function of algae might be damaged. The down-regulation of genes in porphyrin metabolism, photosynthesis, carbon fixation, glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation might inhibit chlorophyll synthesis, photosynthesis, and ATP supply, thereby hindering the growth and metabolism of algae. Moreover, the down-regulation of genes related to nucleotide metabolism and DNA replication might influence the reproduction of algae. These findings provided effective strategies to elucidate toxic mechanisms of contaminants on algae in algal bloom water.

Multi-omics analyses reveal new insights into nutritional quality changes of alfalfa leaves during the flowering period

High-quality alfalfa is an indispensable resource for animal husbandry and sustainable development. Its nutritional quality changes dramatically during its life cycle and, at present, no molecular mechanisms for nutrient metabolic variation in alfalfa leaves at different growth stages have been clearly reported. We have used correlation and network analyses of the alfalfa leaf metabolome, proteome, and transcriptome to explore chlorophyll, flavonoid, and amino acid content at two development stages: budding stage (BS) and full-bloom stage (FBS). A high correlation between the expression of biosynthetic genes and their metabolites revealed significant reductions in metabolite content as the plant matured from BS to FBS. l-Glutamate, the first molecule of chlorophyll biosynthesis, decreased, and the expression of HemA, which controls the transformation of glutamyl-tRNA to glutamate 1-semialdehyde, was down-regulated, leading to a reduction in leaf chlorophyll content. Flavonoids also decreased, driven at least in part by increased expression of the gene encoding CYP75B1: flavonoid 3'-monooxygenase, which catalyzes the hydroxylation of dihydroflavonols and flavonols, resulting in degradation of flavonoids. Expression of NITRILASE 2 (NIT2) and Methyltransferase B (metB), which regulate amino acid metabolism and influence the expression of genes of the glycolysis-TCA pathway, were down-regulated, causing amino acid content in alfalfa leaves to decrease at FBS. This study provides new insights into the complex regulatory network governing the content and decrease of chlorophyll, amino acids, flavonoids, and other nutrients in alfalfa leaves during maturation. These results further provide a theoretical basis for the generation of alfalfa varieties exhibiting higher nutritional quality, high-yield cultivation, and a timely harvest.

Physiological changes and rate of resistance of Acrosiphonia arcta (Dillwyn) Gain upon exposure to diesel fuel

The changes in the morpho-physiological state of green alga Acrosiphonia arcta upon exposure to diesel fuel (DF) at concentrations of 20; 100; 1,000; 2,000; 3,000 of maximum permissible concentrations (MPC) were studied. The main physiological stress markers, such as enzymes of the antioxidant system (AOS), non-enzymatic antioxidants (carotenoids) and free amino acids (as components of plant metabolome) were measured. In general, all concentrations of the petroleum product used changed the activity of the antioxidant system, changed the intensity of physiological processes (photosynthesis, free amino acid synthesis) and also affected the structure of microbiomes inhabiting the surface of algae.

It was shown that the concentration of DF within 1 mg/l (20 MPC) was not lethal as plants were able to maintain physiological activity and the observed changes were reversible.

Although DF exposure caused decreases in superoxide dismutase (SOD) activity, proline concentration and photosynthetic rate, increases in catalase activity and pigment concentration were observed. After the effects of stress disappeared, most physiological parameters were restored, except for carotenoid content.

Higher DF concentrations (100 MPC and higher) caused injury to cell structures and damage to the pigment apparatus. The restoration of functions after the termination of exposure to stress was not achieved. Epiphytic bacterial communities actively responded both to the introduction of a toxicant and to the changing physiological parameters of algae by the change in the numbers of cultured heterotrophic bacteria. The results of this study showed that the concentration of petroleum products in the water decreased to values not exceeding MPC in the presence of algae in the environment.