Study of the salinity acclimation in Dunaliella

Abstract

The purpose of this study is to find out the various acclamatory mechanisms in response to the broad range of salt concentrations in Dunaliella. In 0.8 M NaCl and 1.5 M NaCl concentration, Dunaliella salina KCTC10654BP grew well with the highest number of cell. While D. viridis exhibited the largest number of cell in 2.5 M NaCl and 4.5 M NaCl concentration. In case of Dunaliella salina CCAP 19/18 wild type, mutant and D. bardawil they showed slow growth pattern compare to other three species. Northern blot analysis revealed that Dunaliella salina CCAP 19/18 mutant showed higher expression of zds and lcy genes than wild type which may indicate enhanced expression of zds and lcy genes in mutant are responsible to greater accumulation of β-carotene. Dunaliella salina CCAP 19/18 wild type, mutant and D. bardawil cells became red and increased their size in 4.5 M NaCl concentration. In 4.5 M salt concentration, Dunaliella sp., D. salina KCTC10654BP and D. viridis cells became bigger than cells grown in low salinity. When changes in the content of GB (glycine betaine) were measured under various salt condition, contents of GB were similar to those of glycerol in low salinity. When salt concentration was increased to near saturation, glycerol contents increased more rapidly than GB contents, which indicate that the accumulation of glycerol in Dunaliella is more important than that of GB in high salt conditions. When changes in expression of FeSOD protein and CBR were monitored by western blot analysis under different salinity, the level of FeSOD is increased by salinity in D. salina KCTC10654BP, D. bardawil and D. viridis, but expression of CBR was only observed at 4.5 M salt concentration in Dunaliella sp., Dunaliella bardawil and Dunaliella salina CCAP 19/18. These results indicate that CBR in response of extreme high salinity may involve important role in acclimation of salt stress in Dunaliella.