The Study Of WspA And Its Function In Nostoc Commune

Nostoc commune is a kind of terrestrial nitrogen-fixing cyanobacterium. It exhibites desiccation resistance, and is considered to be a useful model for studying the desiccation tolerance of prokaryotic cells. The isolating the drought-resistant genes from N. commune and exploring their functions would provide candidate genes and theoretical reference for plant genetic engineering.It has been formerly reported N. commune wspA gene is1086bp and encodes361amino acids, but its drought-associated function was not clear. WspA protein is a water stress protein, and is induced by drought stress. A large amount of WspA is also reported to distribute in extracellular glycan sheath, and show β-galactosidase activity.In this research, we attempted to explore the potential drought-reistance-associated function of WspA by heterologously expressing wspA gene into transgenic Arabidopsis. The transgenic Arabidopsis plants were identified by PCR, RT-PCR and Western Blot. The β-galactosidase activity of transgenic Arabidopsis plants was also higher than that in wild-type Arabidopsis. Further, we evaluated the morphology, physiological and biochemical indexes of transgenic Arabidopsis upon drought stress. The transgenic plant showed longer root growth than WT control after treatment for7days on300mM mannitol-added MS solid medium. Also, the MDA and conductivity in leaves of transgenic plants were lower that that in control. These results demonstrated that WspA protein was involved in the drought resistance in transgenic plants. The distribution and location of WspA in transgenic plant were also evaluated by constructing fusion construct of WspA and eGFP and then transforming it into Arabidopsis. It was found WspA protein could be specifically transport to meristematic zone in root tip. The possible role of a predicted C-terminal signal peptide in WspA was further analyzed by fusing the signal peptide with eGFP and the result indicated that it indeed played an important role in WspA’s orientation transport. The distribution and location observation of WspA had suggested the possible reason of longer root elongation under the stress environment in transgenic plants.Nostoc commune, Nostoc flagelliforme and Nostoc sphaeroids, which are close neighbor species, are the most common macroscopic Nostoc. We found that N. fflagelliforme and N. sphaeroids also had several homologous proteins of WspA by western blot analysis, while Nostoc.sp7120and Synechocystis PCC6803had no such homologous proteins. This research suggested WspA protein was possibly unique in macroscopic Nostoc.