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.
Highlights
Phenotypic plasticity is the capacity of a single genotype of an organism to alter its phenotypes in response to different environments[1]
The results revealed that different concentrations of Indole-3-acetic acid (IAA) had divergent effects on the growth of D. komarekii (Fig. 1)
The results showed that the D. komarekii cells and P. pectinatus cells in the control groups did not produce, or only produced a small amount of, lipid droplets, but the large unicells of D. komarekii and P. pectinatus cells both accumulated a large amount of lipid droplets at an IAA concentration of 500 μM (Supplementary Figs 4 and 5)
Summary
Phenotypic plasticity is the capacity of a single genotype of an organism to alter its phenotypes in response to different environments[1]. Yang and his colleagues further address how abiotic factors affect plastic responses to biotic factors They indicated that herbicide exposure and metal (Cu)-contaminated waters both impair antigrazer colonial morphs in S. obliquus. This phenomenon can increase the risk of predation by herbivores, thereby disrupting the inducible phytoplankton community[17,18] They showed that the morphological defense in S. obliquus was enhanced with more eight-celled colonies formed in populations grown in a high-CO2 environment[19]. We proposed that the IAA acts as a diffusible signal in the communication between the microalgae and its associated microorganisms To test this hypothesis, we investigated the induced colony changes, population growth, and physiological changes of Desmodesmus at different IAA concentrations. The sinking rates of Desmodesmus populations cultured in different levels of external IAA were determined
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