Growth, Metabolite Profile, Oxidative Status, and Phytohormone Levels in the Green Alga Acutodesmus obliquus Exposed to Exogenous Auxins and Cytokinins

Abstract

The effects of auxins and cytokinins at the range of concentrations 0.0001-100 µM on Acutodesmus obliquus (Chlorophyceae) cultures were studied. Microalga exhibited sensitivity to cytokinins in the following order: 0.01 µM tZ > 0.1 µM Kin > 1 µM DPU, whereas the hierarchy of auxin activity was: 0.01 µM IAA > 0.1 µM IBA > 0.1 µM PAA. Cytokinins possessed higher stimulating properties on the cell number, whereas auxins increased the size of cells. Differences in the metabolite profiles of the cultures treated with phytohormones were observed. Auxins and cytokinins had a positive effect on the photosynthetic apparatus enhancing the level of chlorophylls, carotenes, and xanthophylls. In comparison with auxins, cytokinins more effectively delayed oxidative damage by increasing the level of non-enzymatic antioxidants (ascorbate, glutathione) and the activity of enzymes scavenging reactive oxidative species (catalase, glutathione reductase, ascorbate peroxidase). On the other hand, auxins stimulated superoxide dismutase activity and provoked hydrogen peroxide generation, which may be involved in cell enlargement. All phytohormones reduced the content of abscisic acid and controlled the level of endogenous auxin and cytokinins suggesting complex interactions. Different dynamics of A. obliquus responses to auxins and cytokinins clearly demonstrated their diverse roles in algal growth and metabolism.

Auxins and Cytokinins Regulate Phytohormone Homeostasis and Thiol-Mediated Detoxification in the Green Alga Acutodesmus obliquus Exposed to Lead Stress

“…www.nature.com/scientificreports www.nature.com/scientificreports/ The results of principal component analysis (PCA) indicated that Pb and exogenous auxins and cytokinins applied with heavy metal possessed strong influence on the levels of endogenous phytohormones in A. obliquus. The intracellular amounts of auxins (IAA, PAA) decreased following Pb stress contributing to growth inhibition www.nature.com/scientificreports www.nature.com/scientificreports/ as previously observed in A. obliquus cultures 3,4,9 . The effect of metals on auxin content and the related alterations in growth and metabolism is extensively explored in vascular plants 21 .…”

“…276-6 was purchased from the SAG Culture of Algae Collection (Germany). The growth conditions and procedures of culture synchronization are the same as previously described 3,4,9,48 . The axenic algal cultures were cultivated in Erlenmeyer flasks with Bold Basal Medium (pH 7.0; 100 mL) 49,50 for 5 days at 25 ± 0.5 °C, in a 16: 8 (light: dark) cycle and illuminated with a light intensity of 50 µMol m −2 s −1 .…”

“…During the experiment, green alga A. obliquus has been grown as an unicellular form. The concentrations of analyzed compounds were selected based on previous experiments 4,9,48 as the most toxic for algal growth in the case of Pb and as the most effective in induction of cell proliferation in case of phytohormones. Therefore, following auxins: 0.01 µM IAA, 0.1 µM IBA and 0.1 µM PAA as well as cytokinins: 0.01 µM tZ, 0.1 µM Kin, and 1 µM DPU were used solely and in combination with 100 µM Pb applied as nitrate form Pb(NO 3 ) 2 .…”

“…Although green microalgae such as Acutodesmus obliquus are less morphologically advanced than vascular plants, they have many similar biochemical processes and responses to abiotic stress, which could potentially be under phytohormone control 3,4 . The presence and/or functions of auxins (i.e., indole-3-acetic acid, IAA; indole-3-butyric acid, IBA; phenylacetic acid, PAA) and cytokinins (i.e., trans-zeatin, tZ; kinetin, Kin; N,N'-diphenylurea, DPU) were confirmed in different microalgal species from Chlorella, Scenedesmus and Acutodesmus genus [5][6][7][8][9] . These phytohormones are the most essential endogenous molecules for modifying physiological and molecular reactions and are critically required by the plant for its survival under heavy metal stress.…”

Co-inoculation of rhizobia, azospirilla and cyanobacteria for increasing common bean production

“…In addition to contributing to BNF, A. cylindrica is able to increase iron solubility by producing siderophores (Wirtz, Treble, & Weger, 2010). Foliar application of the cyanobacterium Anabaena (PCC 7120) and bio-stimulators was found to partly alleviate the harmful impacts of adverse temperature and water stress on growth and physiological activity of willow (Salix viminalis) plants (Piotrowska-Niczyporuk, Bajguz, Kotowska, Bralska, & Talarek-Karwel, 2018). Ghaderiardakani, Collas, Damiano, Tagg, & Graham, (2019) found that the use of algal extracts from Ulva intestinalis as fertilizers should be cautious as its inhibitory effects during plant early development may outweigh any benefits if the concentration of the algal extract is too high.…”