NDH-1-dependent Cyclic Electron Transport Around Photosystem I Is Helpful To Resist Adversity In Nostoc Flagelliforme

Nostoc flagelliforme is a well known highly resistant ability cyanobacteria, simultaneously also has the very high economic value, it has been one of the hot topics in the studies of cyanobacterial. Study on resistance oi Nostoc flagelliforme not only for protection and artificial cultivation of Nostoc flagelliforme plays an important role, but also for crop improvement provides new ideas. The research direction has been under stress conditions from the physiological and morphological changes into the resistance mechanism gradually after these years. In this process, sheath, extracellular polysaccharide, carotene and so on in response under the stress conditions were discovered in succession, making people get certain new understanding on the resistance mechanism of Nostoc flagelliforme.Our laboratory have found that NDH-CET is increased obviously during rehydrated and dehydration process in Nostoc flagelliforme. This implies that NDH-CET may play a role in Nostoc flagelliforme of drought resistance. In order to further studies on whether the NDH-1 complex is responsive to the stress factors of ecological environment, we carried out the experiment, and the results are as follows: We compared ndhK sequences from the close-related species of N. flagelliforme, then get the gene nucleotide sequence and corresponding amino acid sequence by molecular cloning. On the basis of this, we have prepared antibody of NdhK. After that, N. flagelliforme were induced by low carbon, high temperature and high light stress. With the increasing of induction time, an amount of NdhK is up-regulated. At the same time, the height and relative rate of postillumination increase in chlorophyll fluorescence became higher. And the reoxidation level of P700 was decreased. These phenomena demonstrated that the activity and an amount of NDH-1 are induced by these three kinds of stress conditions, suggesting that NDH-1 may be one of the resistance mechanisms of N. flagelliforme. In order to study the possible mechanism of the NDH-1 complex, we do further experiments in Synechocystis 6803. NDH-CET results in proton translocation across the membrane and into the lumen, the resultant proton motive force is used to power ATP synthesis, then the additional ATP was used to repair photosynthetic apparatus and therefore helpful to resist adversity in Synechocystis 6803. NdhD1 and NdhF1 are important subunits that contain proton pumps, what is more, NdhP and NdhQ are known to required for stabilization of the NDH-1L complex. Deletion of these two subunits can reduced the accumulation of proton gradient acrossing the thylakoid membrane, and then reduced the synthesis of ATP. In order to verify this conjecture, we select the high light as a stress factor to carry on the research. Results show that AndhP and AndhQ grow more slowly than WT under high light. The results of the study may indicate that the NDH-CET can power additional ATP synthesis to resist adversity in Nostoc flagelliforme.