Arginine-rich peptides have attracted considerable attention due to their distinct internalization mechanism. It was reported that arginine and guanidino moieties were able to translocate through cell membranes and played a critical role in the process of membrane permeation. In this work, arginine was conjugated to the backbone of chitosan to form a novel chitosan derivative, arginine modified chitosan (Arg-CS). Arg-CS/DNA complexes were prepared according to the method of coacervation process. The physicochemical properties of Arg-CS and Arg-CS/DNA complexes were characterized and the transfection activity and efficiency mediated by Arg-CS/DNA complexes were investigated taking HeLa cells as target cells. Arg-CS was characterized by FTIR and 13 C NMR. Arg-CS/DNA polyelectrolyte complexes were investigated by agarose gel retardation, dynamic light scattering (DLS) and atomic force microscopy (AFM). The results revealed that the Arg-CS/DNA complexes started to form at N/P ratio of 2:1, and the size of particles varied from 100 to 180 nm. The cytotoxicity of Arg-CS and their complexes with plasmid DNA were determined by MTT assay for HeLa cells, and the results suggested that Arg-CS/DNA complexes were slightly less toxic than Arg-CS. Moreover, the derivative alone and their complexes showed significantly lower toxicity than PEI and PEI/DNA complexes, respectively. Taking HeLa cells as target cells and using pGL3-control as reporter gene, the luciferase expression mediated by Arg-CS was greatly enhanced to about 100 folds compared with the luciferase expression mediated by chitosan at different pH media. These results suggest that Arg-CS is a promising candidate as a safe and efficient vector for gene delivery and transfection. chitosan, arginine-modified chitosan, non-viral vector, arginine-rich peptides, gene delivery system

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Astronautical mutagenesis is a new and security agricultural breeding technique in recent decades. There are very large differences in physical environment between space and ground. After returning to the ground, new varieties are bred by the conventional breeding techniques. There are rich genetic types in mutagenesis. In this paper, “Longmu 801” alfalfa seeds were carried by “Shijian-8” recoverable satellite and some new types were selected and bred. The genetic variation of 11 mutated lines and their CK were identified by RAPD analysis, determination of leaf protein concentrates (LPC) and crude protein. For genetic identification, 100 primers were tested and 19 primers were selected in RAPD amplification. The amplified bands and polymorphic sites were rich. Polymorphism points and ratios of polymorphism point were statistical in detail. They were 326 and 15.04% respectively. For quality identification, it was compared with yields of alfalfa LPC and crude protein contents. The results showed that the range of yields of LPC was 6.52%-7.65%, range of nitrogen content was 43.79%-52.38%. Comparing with CK, variation ranges were -3.99%-+12.99% and -4.45%-+12.49%.

The osmotic stress and ion toxicity caused by high salt is one of the major abiotic stress factors that affect the crop growth and development. Na+/H+ antiporter is the key factor in the salt-stress tolerance in organism. It can maintain normal growth and metabolism of organism under high salt stress. PCR was per- formed to clone a plasma membrane Na+/H+ antiporter gene nhaA from Pseudomonas stutzeri, and the plant expression vector pBI121-nhaA was constructed. NhaA gene was trans- formed into soybean growing point via Agrobacterium- mediated transformation. PCR, Southern blot analysis showed that nhaA gene had been integrated into the soybean genome. Salt resistance analysis showed that the relative electronic conductivity of the transformed plants plasma membrane was signify- cantly lower than that of the control under salt stress. While the content of chlorophyll and proline in the transformed plants were significantly higher than that in the controls. The expression of nhaA gene increased the salt stress tolerance of the transgenic soybean and provided excellent candidate genes for improving salt tolerance of crops.