Indole-3-acetic-acid-induced phenotypic plasticity in Desmodesmus algae

Abstract

Phenotypic plasticity is the ability of a single genotype of an organism to exhibit variable phenotypes in response to fluctuating environments. It plays a crucial role in their evolutionary success. In natural environments, the importance of interactions between microalgae and other microorganisms is generally well appreciated, but the effects of these interactions on algal phenotypic plasticity has not been investigated. In this study, it revealed that indole-3-acetic acid (IAA), the most common naturally occurring plant hormone, can exert stimulatory at low concentrations and inhibitory effects at high concentrations on the growth of the green alga Desmodesmus. The morphological characteristics of Desmodesmus changed drastically under exposure to IAA compared with the algae in the control environment. The proportion of Desmodesmus unicells in monocultures increased with the IAA concentration, and these unicells exhibited less possibility of sedimentation than large cells. Furthermore, we discovered that lipid droplets accumulated in algal cells grown at a high IAA concentration. Results also demonstrated that the presence of algal competitor further stimulated inducible morphological changes in Desmodesmus populations. The relative abundance of competitors influenced the proportion of induced morphological changes. The results indicate that phenotypic plasticity in microalgae can be a response to fluctuating environments, in which algae optimize the cost–benefit ratio.

Effects of auxin derivatives on phenotypic plasticity and stress tolerance in five species of the green algaDesmodesmus(Chlorophyceae, Chlorophyta)

“…We found that the algal strains we assayed here have different response patterns to the external IAA. In this study and our previous study, we found that when IAA concentration increased, the mean number of cells per particle of some Desmodesmus species decreased (Chung et al, 2018). The surface-to-volume ratios of the unicells was larger than the colony cells in microalgae.…”

“…We also demonstrated that these unicells exhibited a lower tendency to sedimentation than did large cells and that shrinkage may facilitate nutrient uptake and light capture (Chung et al, 2018). However, whether other coenobial algal species of Desmodesmus use the same strategy to overcome stress remains unknown.…”

“…In a previous study, we performed a dose-response analysis to determine the fitness effects of IAA on the coenobial alga D. komarekii (Chung et al, 2018). The results revealed that different concentrations of IAA had different effects on the growth and morphological changes of D. komarekii.…”

“…Notably, not only plants but also bacteria, fungi (including yeast), and even some microalgae produce or respond to IAA (Fu et al, 2015). Researchers have hypothesized that the microbes sense environmental IAA concentrations to determine the cell density of its competitors (Spaepen, Vanderleyden & Remans, 2007;Fu et al, 2015;Chung et al, 2018). Thus, IAA has been speculated to be a signal that coordinates microbial behavior to enhance protection against damage by adverse conditions (Bianco et al, 2006;Chung et al, 2018).…”

“…Researchers have hypothesized that the microbes sense environmental IAA concentrations to determine the cell density of its competitors (Spaepen, Vanderleyden & Remans, 2007;Fu et al, 2015;Chung et al, 2018). Thus, IAA has been speculated to be a signal that coordinates microbial behavior to enhance protection against damage by adverse conditions (Bianco et al, 2006;Chung et al, 2018). We proposed that the physiological changes in response to IAA confers a fitness advantage by promoting the ability of Desmodesmus strains to survive in their niches that often undergo fluctuations in environmental factors, such as temperature, osmotic pressure, reactive oxygen species, and pH changes.…”