The Preliminary Study On The Relationship Of NO And The Salt-stress Physiology Of Dunaliella Salina

In this study, the salt-resistance of Dunaliella salina in the view of NO was preliminary investigated. And we supposed to find whether NO, which is recognized as the new biological signal molecular, plays a role in the salt-resistance of Dunaliella salina.The growth and photosynthetic parameters of Dunaliella salina in different salinities were measured respectively. The results showed that Dunaliella salina could thrive in a wide range of salinities. And in the salinity of 60%o, compared with 5‰,10‰,30‰, 100‰,150‰,200‰,250‰and 300‰, the status of growth and photosynthesis were best. It also showed that Dunaliella salina would be under salt stress in whether too high or too low salinity, therefore the growth and photosynthesis would be influenced. Simultaneously, the NO production of Dunaliella sanila in different salinities was measured. The results showed that the treatment groups of 5‰,10‰,30‰,100‰, 150‰,200‰,250‰and 300‰, which were all under various levels of salt stress contrast to 60%o, all produced more NO than 60‰. Moreover, the high level of salt stress was corresponding to the more production of NO. These results showed that NO could probably play a role in the salt resistance of Dunaliella sanila.When under salt stress, Dunaliella sanila can start the responses of stress resistance. For instance, the enzymatic activities of the antioxidant enzymes will be increased, like SOD (Super Oxide Dismutase) and CAT (Catalase). What's more, the accumulation of un-eliminated substances produced under stress, like MDA (Malonaldehyde), will be increased. The relationship between NO and SOD, CAT, MDA was studied in this chapter. And the results showed that the activities of SOD and CAT were lower than the control group when adding SNP (NO donor), so were the contents of MDA. However, the activities of SOD and CAT were higher than the control group when adding c-PTIO (NO scavenger), so were the contents of MDA. The phenomenon indicated that exogenous NO of proper concentration participated in the salt resistance of Dunaliella salina and protected the algae cells from damage. The algae cells recovered to the normal physiological activities progressively. And the activities of SOD and CAT which were generated to resist the salt stress were reduced. Hence the contents of MDA were also decreased. The effect of the protection can further demonstrate that NO play a positive role in the salt stress resistance of Dunaliella salina.In this paper the generation pathway of NO in salt stress of Dunaliella salina was studied. In plants, NO was mainly produced through the catalytic reactions of two enzymes, that is NOS-like (Nitric Oxide Synthase) and NR (Nitrate Reductase). The production of NO in Dunaliella salina was decreased contract to control when adding L-NAME (NOS inhibitor) and Na2WO4 (NR inhibitor). This result here about the activities of the main enzymes related to NO generation, NR and NOS-like, indicated that they both are potential contributors to the cellular production of NO in salt stress of Dunaliella salina. The results showed that the NR played a leading role when the algae endured light salt- stress. It also manifested that lower unicellular algae had the similar mechanism of NO generation to the higher plants. The Dunaliella salina in the salinity of 300%o, in which the algae endured greater stress, utilized NOS-like as the leading enzyme to generate NO. This result demonstrated that NOS was induced plentifully in high salinity. Furthermore, NOS activity was more common in animals and bacteria than in plants. So it can be come to a conclusion that lower unicellular algae had the similar physiological metabolic processes of NO to animals and bacteria.In the first growth phase, Dunaliella salina had unstable Physiological conditions and weak ability of resistance. In this phase most concentrations of SNP (50μM) would strongly inhibited the algae growth. But in the exponential phase, the algae cells grew and divided exuberantly and had strong ability of resistance. In this phase all concentrations of SNP (10μM,50μM,100μM,150μM) adding in this study had no obviously inhibition effect on the algae growth.β-carotene and glycerol, which is the two metabolites of Dunaliella salina, did not show any obviously promotion or inhibition rule when adding SNP and c-PTIO. The possible reason might be that:as the metabolites of Dunaliella salina.β-carotene and glycerol were only accumulated in a fixed growth phase and always after some external stimulation. But the effect of SNP and c-PTIO was transient, which was not too long enough to affect the accumulation of the two metabolites.NO signal was a complicated process. Not only because it's special action, but also the difficult detecting, we just did a preliminary research on NO in Dunaliella salina. Even so, the results showed certain rules that when in salt stress Dunaliella salina generated NO through the enzymes of NOS and NR. The NO participated in the salt stress resistance and could protect the algae cells from damage. However, the further study focus on the questions, like how NO protect the algae cells, how the NO signal transmit and the details of the signal transmission, should be done deeply. Now the studies on NO in lower marine algae were still relatively less and this is a new field to broaden the role of NO which is supposed to be involved in a large broad physiological field. Therefore, the studies in this field are valuable and the future research can use the advanced methods in Molecular Biology and Biochemistry to carry out the in-depth exploration.