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Updated: May 20, 2026

Measurements of Physiological Stress Responses in C. Elegans
Published on: May 21, 2020
Ethylene-mediated hormesis uncouples biomass growth and paramylon biosynthesis in Euglena gracilis by modulating
Jiangyu Zhu1, Xinyue Guo1, Yifei Cai1
1School of Food Science and Engineering, Yangzhou University, No. 196 Huayang West Road, Hanjiang District, Yangzhou 225127, China.
Abstract:
High-value paramylon production in Euglena gracilis is typically constrained by the inverse relationship between rapid biomass growth and metabolite accumulation. This study investigates the regulatory effect of the phytohormone ethylene (supplied as ethephon, ETH) on E. gracilis physiology and paramylon (β-1,3-glucan) biosynthesis. Supplementation with 10 mg·L-1 ETH induced a hormetic response, increasing biomass production by 19.19%. This growth enhancement coincided with a morphological transition toward elongated cells exhibiting higher surface-to-volume ratios. Physiologically, ETH treatment improved photosynthetic performance by increasing chlorophyll content, photosystem II efficiency (Fv/Fm), and electron transport fluxes. Additionally, ETH modulated redox homeostasis by upregulating superoxide dismutase activity, which effectively decreased intracellular reactive oxygen species and lipid peroxidation. At the molecular level, ETH significantly upregulated the expression of β-1,3-glucan synthase genes (EgGSL1 and EgGSL2). As a result, paramylon yield increased by 39.33% without inhibiting cell growth. These findings demonstrate that ETH signaling coordinates carbon partitioning by simultaneously enhancing photosynthetic energy supply and activating storage polysaccharide biosynthesis, providing an effective strategy for high-efficiency microalgal bioprocesses.
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