Exogenous expression of the wheat chloroplastic fructose-1,6-bisphosphatase gene enhances photosynthesis in the transgenic cyanobacterium, <Emphasis Type="BoldItalic">Anabaena</Emphasis> PCC7120

The paper reports a study on the genetic regulation of photosynthesis by introducing the gene encoding wheat chloroplastic fructose-1,6-bisphosphatase (FBPase) into the cyanobacterium Anabaena PCC7120. The gene was RT-PCR amplified from wheat and modified by replacement of the 5′-terminal encoding sequence with optimal and A/T-rich codons to promote prokaryotic expression. The resultant FBPase gene was ligated downstream of the strong promoter, PpsbA of expression vector pRL-439, then inserted into of shuttle vector pDC-08. The resulting shuttle expression vector (pDC-fbp) was transferred into the filamentous, heterocystour cyanobacterium, Anabaena PCC7120, by the tri-parental conjugation transfer method. Protein expression of FBPase in the transgenic Anabaena was 126.5% higher than in wild type cells, and the enzyme activity of transgenic cells was 1.41-fold higher than that of wild type cells. Under atmospheric conditions of 360 μmol mol⁻¹ CO₂, Anabaena cells overexpressing the FBPase gene further showed increases in net photosynthesis (117.2%) and true photosynthesis (122.5%) as compared to wild type cells. In addition, transgenic Anabaena grew faster and contained more Chl a than did wild type cells. Together, these results indicate that introduction of the wheat chloroplastic FBPase gene into Anabaena increase photosynthesis and cell growth; furthermore, these trends were more evident under stress condition (higher CO₂ concentration). This is the first report of enhanced photosynthesis in cyanobacteria expressing genes from higher plants.     

Time-Related Transcriptome Analysis of B. subtilis 168 During Growth with Glucose

Gene expression in Bacillus subtilis from late exponential to stationary phase was monitored by DNA microarrays with samples taken from the culture in LB broth with glucose supplement to prevent sporulation. Three major patterns of gene expression as revealed in this study were consistent to the expression profiling of PerR/Spx regulons and three major sigma factors—SigA, SigB, and SigW. Expression of most SigA-dependent house-keeping genes was significantly decreased and remained at low levels in the stationary phase. The sigB gene and additional genes of the SigB regulon for stress response exhibited a distinct pattern of transient induction with a peak in transition phase. The majority of induced genes after cessation of SigB-dependent surge were subjected to regulation by SigW, PerR, and Spx in response to oxidative stress. No induction of spo0A and skfA regulons supports the suppression of sporulation and cannibalism processes in the stationary phase by glucose supplement. In summary, these results depicted complicated strategies by cells to adapt changes from the fast growing exponential phase toward the stationary phase. The absence of programed cell death and sporulation greatly facilitated data analysis and the identification of distinct expression patterns in the stationary phase of growth in B. subtilis.     

The response regulator RpaB binds the high light regulatory 1 sequence upstream of the high-light-inducible <Emphasis Type="Italic">hliB</Emphasis> gene from the cyanobacterium <Emphasis Type="Italic">Synechocystis</Emphasis> PCC 6803

Cyanobacteria, like other photosynthetic organisms, respond to the potentially damaging effects of high-intensity light by regulating the expression of a variety of stress-responsive genes through regulatory mechanisms that remain poorly understood. The high light regulatory 1 (HLR1) sequence can be found upstream of many genes regulated by high-light (HL) stress in cyanobacteria. In this study, we identify the factor that binds the HLR1 upstream of the HL-inducible hliB gene in the cyanobacterium Synechocystis PCC 6803 as the RpaB (Slr0947) response regulator.