Transcriptome dynamics and hub genes of green alga Nannochloris sp. JB17 under NaHCO3 stress

Abstract

Soil salinization and alkalization are major problems in crop production. To gain insights into the mechanisms of saline-alkaline tolerance, we investigated the molecular response of a highly stress tolerant green alga, Nannochloris sp. JB17 (JB17) to NaHCO3. Results indicated that JB17 cells retain a high level of cell viability when subjected to a high concentration (300 mM) of NaHCO3. A transcriptome analyses was conducted of JB17 cells that were subjected to either 50 mM or 300 mM NaHCO3 for 4 h, 24 h or 72 h. Thousands of differentially expressed genes (DEGs)11DEGs: Differentially expressed genes. were identified, among which, 134 highly expressed DEGs were mainly enriched in photosynthesis-related processes. Gene co-expression analysis revealed the unique molecular profile of JB17 cells subjected to NaHCO3 stress. Detailed analyses of the long-term and high concentration NaHCO3 related modules indicated that the key pathways and hub genes were related to antioxidant capacity, carbohydrate metabolism, and cell division. Corresponding physiological experiments revealed that the antioxidant enzymes activity and the population of palmelloid cells significantly increased in JB17 cells under NaHCO3 stress. Our data indicate that JB17 cells actively support photosynthesis and increase reactive oxygen species scavenging activity to survive in the presence of NaHCO3. These results provide information on the regulatory mechanisms associated with saline-alkaline tolerance in Nannochloris.