Desiccation-Induced Oxidative Stress Causes Metabolic Flux in the Terrestrial Green Alga Trentepohlia sp., Suggesting Extensive Metabolic Reprogramming for Stress Adaptation.

In the present investigation, we report the impact of desiccation stress on the terrestrial green alga Trentepohlia sp. Stress imposition for a period of 7 d until the relative water content (RWC) of the algal thalli reached < 15% resulted in a substantial change in morphological attributes, stress markers such as reactive oxygen species (ROS), oxidative stress markers, antioxidant metabolism, and metabolic responses. Desiccation stress caused extensive changes in algal thalli, reflected in a loss of color and the appearance of white patches compared to the control. Microscopic studies revealed a significant impact of desiccation stress on the algal filaments, manifested by bending and increased translucency due to the loss of cytoplasmic contents. Although desiccation stress did not have a statistically significant effect on photosynthetic pigment levels, it significantly increased ROS production and elevated levels of oxidative stress markers. Under high ROS levels and substantial oxidative stress, desiccation significantly increased the antioxidant metabolism in the alga, compared to the control. The HRLC-MS and 1H-NMR-based metabolic analysis clearly showed that desiccation stress induced a comprehensive metabolic reprogramming, connecting diverse pathways involved in amino acid, lipid, sulfur, and carbohydrate metabolism, demonstrating stress adaptability through metabolic reprogramming. The results suggested that Trentepholia sp. is a desiccation-responsive green alga that can endure stress by upregulating antioxidant defense and through substantial metabolic reprogramming.