Physiological and transcriptomic responses of soil green alga Desmochloris sp. FACHB-3271 to salt stress

Abstract

Salinity, a rising global threat to agriculture exacerbated by climate change, may be mitigated through salt-soil bioremediation using microalgae. Most studies on stress responses have focused on aquatic algae, leaving soil microalgae largely unexplored. This study investigates the short- and long-term salt stress responses in the salt-tolerant soil microalga Desmochloris sp. FACHB-3271, combining phylogenetic, physiological, and biochemical analyses. Under salt stress, Desmochloris sp. showed sustained growth, with elevated photosynthetic activity and increased polysaccharide, soluble proteins, and total lipid contents. Linoleic acid was the predominant fatty acid, comprising 48.23 % of the total lipids. Long-term salt stress enhanced energy metabolism (chlorophyll synthesis, glycolysis) and osmotic regulation (fatty acid synthesis and degradation, starch and sucrose synthesis), while short-term stress induced dynamic changes. Three signaling pathways (cAMP, MAPK, and ABC transporters) were identified as regulators of salt stress changes. Notably, genes related to vitamin B12 for synthesis exhibited significant changes. These findings provide insights into the salt stress mechanisms of soil microalgae, offering genetic resources for saline-alkali soil remediation, for genetic modification of microalgae for biofuel production and novel approaches to gene discovery in non-genome-referenced algae.