Polycistronic strategy for cyanobacterial expression vector construction: Co-transcription of a human gene and a selective marker gene

A polycistronic expression vector, pKGA-NTF1, was constructed for the cyanobacterium. Within this vector, the spectinomycin/streptomycin resistance gene (aadA) facilitated the selection of transformants when co-transcribed with favorite genes. A natural glnA gene was selected as the platform to introduce the plasmid into a neutral site of the Synechococcus sp. PCC 7002 chromosome. Function of the vector was demonstrated by the insertion of a modified human Trefoil factor 3 gene (NTF1) to upstream of the aadA gene and by the analyses of the transformed strains. Antibiotics resistance assays showed that the dicistronic expression cassette conferred high spectinomycin resistance to both the E. coli cells and the Synechococcus cells. PCR analysis and Western-blot analysis were carried out to confirm the integration and expression of the NTF1 gene, respectively. Through simple molecular manipulations, the artificial polycistronic structure described here can be conveniently used to express other favorable genes or operons in cyanobacteria, and to study the cyanobacterial gene expression as well.     

转基因鱼腥藻7120光异养生长的研究

研究了不同有机碳源对转基因鱼腥藻７１２０生长的影响,在此基础上进行了光异养条件的优化,并研究了外源添加剂Ｌ－精氨酸、生长激素２,４－Ｄ与ＫＴ对藻细胞生长的影响。结果表明：蔗糖和葡萄糖能促进藻体的生长;最优碳氮源组合为葡萄糖６ｇ／Ｌ、ＮａＮＯ３１．５ｇ／Ｌ,经高压灭菌;Ｌ－精氨酸不支持藻体的光异养生长;一定含量的２,４－Ｄ与ＫＴ能促进藻体在光异养条件下的后期生长。     

Effect of iron deficiency on heterocyst differentiation and physiology of the filamentous cyanobacterium<Emphasis Type="Italic">Anabaena</Emphasis> sp. PCC 7120

The effect of iron deficiency on heterocyst differentiation and some physiological properties of the filamentous cyanobacteriumAnabaena sp. PCC 7120 was investigated. Under moderate iron limitation conditions, achieved by addition of iron chelator 2, 2′-Dipyridyl (<80 μmol/L) led to delayed heterocyst differentiation, no heterocyst differentiation was observed under severe iron limitation conditions, when the concentration of 2,2′-Dipyridyl in the medium was more than 100 μmol/L. it seemed that there are certain iron-regulated genes or operons whose function is to control heterocyst development. In addition, iron deficiency impaired the growth. Low iron cells had a decrease in the quantities of pigment content (chlorophyll and phycocyanin content), the whole cellin vivo absorbance spectra confirmed the decrease, the protein electrophoretic profiles revealed that iron-deficient cells had less protein bands, with the increase of 2,2′-Dipyridyl, the protein bands was more and more less. And differently, iron deficiency also caused an increase of ROS (Reactive Oxygen Species) and SOD activity, it suggests that iron deficiency led to oxidative stress, which generally occured under high-iron conditions. Foundation item: Supported by the National Natural Sciences Foundation of China (30070154), the Frontier Science Projects Programme of the Institute of Hydrobiology, the Chinese Academy of Sciences (220316), State Key Project on Cyanobacterial Bloom Control in Lake Danchi (K9905-35-01) Biography: Xu Wenllang (1974-), male, Ph. D. research direction: molecular genetics of eyanobacteria.     

基于SVD和伪随机循环链的图像认证水印算法

针对矩阵的行列互换使得奇异值分解(SVD)后的奇异值不变,从而由奇异值直接产生水印安全性不高,以及基于SVD的图像认证水印算法把块水印嵌入本图像块的最低有效位,从而很难抵抗矢量量化攻击,提出了基于SVD和由Logistic混沌系统构成伪随机循环链的图像认证水印算法.首先通过Logistic混沌系统调制图像,使得图像矩阵唯一,然后将调制后图像块奇异值生成的块水印嵌入伪随机循环链对应图像块最低有效位.实验结果显示,该算法提高了水印的安全性,不仅能够准确定位,而且可以有效抵抗矢量量化攻击.