Multi-omics insight into the adaptation mechanism of desert cyanobacterium Chroococcidiopsis sp. ASB-02 under...

Soil salinity is an environmental stress severely restricting organism growth and causing ecological deterioration. However, Chroococcidiopsis sp. can grow in various salt-rich deserts and is known for extreme environmental tolerance. Currently, there is little information about its salt adaptation mechanism. To address this issue, we conducted investigation at multiple levels, including phylogenetics, physiology, transcriptomics, and metabolomics, to gain understanding of its evolution, degree of salt tolerance, and study salt adaptation mechanism of Chroococcidiopsis sp. ASB-02. The results showed that Chroococcidiopsis sp. ASB-02 exhibited high survival rates under high salt stress and could grow even in 600 mM NaCl, which is 3-6 times than the salt limit of other desert cyanobacteria. Multi-omics analyses revealed that high salt enhanced the expression of PSII repair genes, activated SuS sucrose synthesis and TreS trehalose synthesis pathways, which help to reduce PSII damage, maintaining stable PSII activity, and facilitating osmoregulation. In addition, in response to higher salt concentration (600 mM NaCl), Chroococcidiopsis sp. ASB-02 activated Na⁺/H⁺ transporters and ion channel genes to regulate intracellular ion concentrations. To counter salt-induced oxidative stress, Chroococcidiopsis sp. ASB-02 employed distinct antioxidant strategies based on salt concentration. At 300 mM NaCl, sodA2 and katG genes mainly played roles, whereas at 600 mM NaCl, gor2 and grxB of glutaredoxin system, as well as trxB and ntrC of thioredoxin system played key roles in mitigating oxidative damage. This study clarified the salt adaptation mechanism of Chroococcidiopsis sp. ASB-02 and revealed crucial biological pathways with multi-omics insight, which may be helpful to develop salinization bioremediating with cyanobacteria.