The effect of different promoter-sequences on transient expression of gus reporter gene in cultured barley (Hordeum vulgare L.) cells

The cauliflower mosaic virus 35S (35S) and the enhanced 35S (E35S) promoters fused with maize alcohol dehydrogenase (Adh1) intron1 or maize shrunken locus (sh1) intronl along with maize Adh1 and rice actin (Act1) promoters fused to their respective first introns were tested for transient expression of the E.coli -glucuronidase (gus) reporter gene in cultured barley (Hordeum vulgare L) cells. The plasmids, carrying the respective promoterintron combinations to drive the gus fused to nopaline synthase (nos) terminator, were introduced into cultured barley cells using a particle gun. The rice Act1 promoter with its first intron gave the highest expression of all promoter intron combinations studied. This was followed by the E35S promoter and no significant differences were observed between the other two promoters tested. The rice actin promoter is now being used to drive selectable marker genes to obtain stably transformed cereal cells.NRCC No. 36482     

A new and efficient phosphate starvation inducible expression system for Lactococcus lactis

A new expression system for Lactococcus lactis was developed. The system is based on a phosphate starvation inducible pstF promoter of L. lactis MG1363. Intracellular beta-galactosidase and secreted alpha-amylase were produced using this tightly regulated system. No evidence of regulatory sites in regions of the 5'-end of the pstF coding sequence was found. High expression levels of the beta-galactosidase gene were obtained using the original pstF RBS in a phosphate-depleted medium. The results suggested that with the phosphate starvation inducible system, it is possible to achieve expression levels comparable to the ones obtained with the widely used nisin-controlled gene expression system (NICE). A specific beta-galactosidase activity of 670 microkat g(-1) using a phosphate-depleted medium and an alpha-amylase activity of 3.6 microkat l(-1) in a bioreactor cultivation were produced. The advantages of the current expression system include that no prior removal of phosphate from the medium in bioreactor scale is required, and no additions of inducing agents are needed. Furthermore, the system can be operated in L. lactis without introduction of regulatory genes into the host.     

Identification of three cDNA clones expressed in the leaf extension zone and with altered patterns of expression in theslender mutant of barley: a tonoplast intrinsic protein, a putative structural protein and protochlorophyllide oxidoreductase

Three cDNA clones have been isolated on the basis of altered patterns of expression in the leaf extension zone of the developmental mutant,slender barley, compared with the wild type. mRNAs corresponding to two of the cDNAs, 7s and 8s, are increased inslender compared with normal. 7s encodes a putative -TIP and is expressed throughout the elongation zone. -TIPs form transmembrane channels which allow the passive transfer of water. Although expression of 7s was increased inslender leaf tissue, the increase was much less extreme than that shown by Phillips and Huttly (1994) following the application of GA to an extreme dwarf ofArabidopsis. 8s is maximally expressed in the region of early cell elongation and has 66% encoded protein identity with MFS18, a cDNA encoding a putative cell wall structural protein isolated from male flowers of maize. Both 8s and MFS18 encode small (128 amino acids) basic proteins rich in glycine, alanine, proline and serine. mRNA corresponding to the third cDNA, 24n, is present at a greatly reduced level inslender compared with normal and encodes protochlorophyllide oxidoreductase (POR). POR catalyses the conversion of protochlorophyllide into chlorophyllide. The reduced level of POR mRNA is not correlated with a similar reduction in expanded leaf blade chlorophyll levels. Western analysis identified two POR proteins present in light-grown seedlings. Whilst the larger of the proteins is present throughout most of the leaf, the smaller protein mimics the mRNA results, being both maximally present in the elongation tissue and present at a reduced level inslender. An antagonistic relationship between chlorophyll biosynthesis and extension growth is suggested.     

Quantitative transient gene expression: Comparison of the promoters for maize polyubiquitin1, rice actin1, maize-derivedEmu andCaMV 35S in cells of barley,maize and tobacco

The particle gun approach was used for the quantification of promoter efficiency in a test system for transient gene expression. β-Glucuronidase was used as reporter gene for determining promotote strength. The variability inherent in this gene transfer system was considerably reduced by calculating a transformation efficiency factor given by the expression of a cotransferred second reporter gene (firefly luciferase). The calibration of β-glucuronidase activity by the transformation efficiency factor caused a lower statistical variance of the values and allowed reliable results to be obtained with a smaller set of repetitions. The CaMV 35S promoter (as a control) and the monocot-specific promoters for maize polyubiquitin1, rice actin 1 and the maize-derivedEmu were characterized and compared with respect to expression strength, as tested under identical conditions in suspension cell cultures of maize, barley and tobacco. Compared to the 35S promoter, the monocot-specific promoters show up to 15-fold higher expression in maize and barley but give only weak expression in tobacco. No expression was found for the rice actin 1 promoter in tobacco. The level of reporter gene expression is influenced by the osmotic potential in the agar medium. For theEmu promoter, the calibrated β-glucuronidase activities remained mearly constant at low sucrose concentrations. Above 8% sucrose, the calibrated activities increased steadily with increasing osmotic conditions, reaching a three-to four-fold higher level at the highest sucrose concentration (32%) as compared to the standard concentration (4% sucrose) in the medium.     

Cloning of α-amylase gene from Schwanniomyces occidentalis and expression in Saccharomyces cerevisiae

The cloning of α-amylase gene ofS. occidentalis and the construction of starch digestible strain of yeast,S. cerevisiae AS. 2. 1364 with ethanol-tolerance and without auxotrophic markers used in fermentation industry were studied. The yeast/E.coli shuttle plasmid YCEp1 partial library ofS. occidentalis DNA was constructed and α-amylase gene was screened in S.cerevisiae by amylolytic activity. Several transformants with amylolysis were obtained and one of the fusion plasmids had an about 5.0 kb inserted DNA fragment, containing the upstream and downstream sequences of α-amylase gene fromS. occidentalis. It was further confirmed by PCR and sequence determination that this 5.0 kb DNA fragment contains the whole coding sequence of α-amylase. The amylolytic test showed that when this transformant was incubated on plate of YPDS medium containing 1 % glum and 1 % starch at 30°C for 48 h starch degradation zones could be visualized by staining with iodine vapour. α-amylase activity of the culture filtratate is 740–780 mU/mL and PAGE shows that the yeast harboring fusion plasmids efficiently secreted α-amylase into the medium, and the amount of the recombinant α-amylase is more than 12% of the total proteins in the culture filtrate. These results showed that α-amylase gene can be highly expressed and efficiently secreted inS. cerevisiae AS. 2.1364, and the promotor and the terminator of α-amylase gene fromS. occidentalis work well inS. cercvisiac AS. 2.1364.     

A simple diffusion test for soil phosphorus availability

The availability of phosphorus to plants was estimated by a new method based on the diffusion of P from a thin layer of water-saturated stationary soil to a disc of iron oxide coated filter paper. Twenty-one acid Finnish soil samples were tested using four modifications of the method which differed in the duration of the diffusion time and in the thickness of the soil layer. The new diffusion tests were compared with other soil P testing methods and evaluated as indicators of the availability of P to pot-grown barley and oats. Close linear correlations were found between the initial (18 or 42 h) P diffusion rate and the water extractable P contents determined at the extraction ratios of 1:10 and 1:60, respectively (r=0.97–0.99). The amounts of P obtained by the new method were small when the diffusion time was short, but after prolonged diffusion (1 week) the test values were close to the amounts of P taken up by plants. The relationships of plant yield and P uptake with soil P test values were affected by soil acidity. Although the original soil P test values were significantly correlated, the accuracy of all methods drastically improved when the interfering effect of soil acidity was taken into account using a simple pH-correction model. The correlation coefficients (r) between the test values of diffusible P in soil and the uptake of P by plants increased up to 0.97.     

Characterization of human and rat immortalized clones of parotid acinar cells with respect to specific proteins and their mRNAs,and receptor-linked adenylate cyclase

Summary This study reports the isolation and characterization of a rat nontumorigenic parotid acinar cell clone (2RSG), a human nontumorigenic parotid acinar cell clone (2HPC8), and a human tumorigenic acinar clone (2HP₁G). The levels ofα-amylase mRNAs detected when usingα-amylase cDNA of 1176 and 702 bp for hybridization were higher in 2RSG and 2HPC8 cells than their respective whole parotid glands. The level of these mRNAs decreased in 2HP₁G cells. In contrast toα-amylase mRNAs levels, theα-amylase activity in cultured acinar cells was extremely low in comparison to whole glands, irrespective of species or cell status. The levels of proline-rich protein (PRP) mRNA and parotid secretory protein (PSP) mRNA detected when using PRP cDNA of 600 bp and PSP cDNA of 805 bp for hybridization were higher in 2RSG cells than those in rat parotid glands; the reverse was observed in 2HPC8 cells and human parotid glands. The levels of PRP mRNA and PSP mRNA in 2HPC8 and 2HP₁G acinar cells were similar. The level of mRNA was not detectable in murine neuroblastoma cells (NBP2) using the sameα-amylase cDNA, PRP cDNA and PSP cDNA for hybridization. The PSP level in rat parotid gland was lower than that found in 2RSG cells; the reverse was observed in 2HPC8 cells and human parotid glands. The level of PSP in 2HP₁G cells was higher than that found in 2HPC8 cells. Isoproterenol increased the cAMP level in 2RSG, 2HPC8, and 2HP₁G clones, being most effective in 2RSG cells, and least effective in 2HPG cells. Prostaglandin E₁ (PGE₁) also increased cAMP level, being most effective in 2HPC8 cells and ineffective in 2HP₁G cells, suggesting that the PGE₁ receptor-linked adenylate cyclase becomes inactive upon transformation. These results suggest that the three clonal acinar cells from rat and human parotid glands reported here can be useful in comparative studies on regulation of growth, differentiation, and transformation.     

Expression and secretion of barley α-amylase and A.niger glucoamylase in Saccharomyces cerevisiae

cDNAs of barley α-amylase andA. niger glucoamylase were cloned in oneE. coli-yeast shuttle plasmid resulting in the construction of expression secretion vector pMAG15. pMAG15 was transformed intoS. cerevisiae GRF18 by protoplast transformation. The barley α-amylase andA. niger glucoamylase were efficiently expressed under the control of promoter and terminator of yeast PGK gene and their own signal sequence. Over 99% of the enzyme activity expressed was secreted to the medium. The recombinant yeast strain, S.cerevisiae GRF18 (pMAG15), hydrolyzes 99% of the starch in YPS medium containing 15% starch in 47 h. The glucose produced can be used for the production of ethanol. Project supported by the Guangdong Natural Science Foundation.     

Efficient and sensitive assay for T-DNA-dependent transient gene expression

We describe here a very sensitive and reproducible method to detect the efficiency ofAgrobacterium-mediated T-DNA transfer. This method is based on a quantitative assay of β-glucuronidase activity produced in the plant cell upon transfer of T-DNA carrying a specialuidA gene construct. Analysis of the transfer efficiency of a transfer-proficient bacterium compared with that of the same bacterium diluted at different ratios with a transfer-defective bacterium shows a high sensitivity of the β-glucuronidase activity in the plant. Five orders of magnitude in T-DNA transfer efficiency can be covered when the activity is measured combining the fluorimetric MUG assay (for high activity) and the histochemical X-Gluc assay (very sensitive for low activity).     

Transient expression of foreign genes in rice,wheat and soybean cells following particle bombardment

The development of an efficient transformation system is a prerequisite for the molecular analysis of gene expression in plants. In crop plants, this development has been hindered by difficulties encountered both in whole plant regeneration from protoplasts and in the general insusceptibility of monocots to Agrobacterium-mediated transformation. We have circumvented these difficulties by transferring foreign genes directly into the intact cells (with cell walls) of three important crop plants including rice, wheat and soybean by a particle bombardment device. Oryza sativa and Triticum monococcum cells were bombarded with accelerated tungsten particles coated with plasmids containing a -glucuronidase gene as the reporter. Blue transformed cells were detected in an in situ enzyme assay. The number of blue cells was next used as a convenient criterion to study several factors affecting gene transfer efficiency. After optimal conditions were defined, gene transfer into intact cells of O. sativa, T. monococcum and Glycine max was successfully carried out with chloramphenicol acetyltransferase (CAT) gene as the reporter.     

A major cysteine proteinase, EPB, in germinating barley seeds: structure of two intronless genes and regulation of expression

The barley cysteine proteinase B (EPB) is the main protease responsible for the degradation of endosperm storage proteins providing nitrogenous nutrients to support the growth of young seedlings. The expression of this enzyme is induced in the germinating seeds by the phytohormone, gibberellin, and suppressed by another phytohormone, abscisic acid. In situ hybridization experiments indicate that EPB is expressed in the scutellar epithelium within 24 h of seed germination, but the aleurone tissue surrounding the starchy endosperm eventually becomes the main tissue expressing this enzyme. The EPB gene family of barley consists of two very similar genes, EPB1 and EPB2, both of which have been mapped to chromosome 3. The sequences of EPB1 and EPB2 match with the two previously published cDNA clones indicating that both genes are expressed. Interestingly, neither of these genes contain any introns, a rare phenomenon in which all members of a small gene family are active intronless genes. Sequence comparison indicates that the barley EPB family can be classified as cathepsin L-like endopeptidases and is most closely related to two legume cysteine proteinases (Phaseolus vulgaris EP-C1 and Vigna mungo SHEP) which are also involved in seed storage protein degradation. The promoters of EPB1 and EPB2 have been linked to the coding sequence of a reporter gene, GUS, encoding -glucuronidase, and introduced into barley aleurone cells using the particle bombardment method. Transient expression studies indicate that EPB promoters are sufficient to confer the hormonal regulation of these genes.     

Trypanosoma brucei brucei: A comparison of gene expression in the liver and spleen of infected mice utilizing cDNA microarray technology

Trypanosoma brucei brucei, the infectious agent of the disease known as Nagana, is a pathogenic trypanosome occurring in Africa, where it causes significant economic loss to domesticated livestock. Although many studies on the histopathology of organs of mice infected with T. b. brucei have been reported, little work has been done regarding gene expression in these organs in infected mice. In this paper, we describe the use of cDNA microarray to determine gene expression profiles in the liver and spleen of mice infected with T. b. brucei (STIB 920) at peak parasitaemia (12 days after infection). Our results showed that a total of 123 genes in the liver and 389 genes in the spleen were expressed differentially in T. b. brucei infected mice. In contrast, however, in an acute infection in mice caused by Trypanosoma brucei evansi, a species genetically related to T. b. brucei, 336 genes in the liver and 190 genes in the spleen were expressed, differentially, indicating that the liver of mice was more affected by the acute T. b. evansi infection whilst the spleen was more affected by the subacute T. b. brucei infection. Our results provide a number of possible reasons why mice infected with T. b. evansi die sooner than those infected with T. b. brucei: (1) mice infected with T. b. evansi may need more stress response proteins to help them pass through the infection and these are probably excessively consumed; (2) proliferating cell nuclear antigen was more down-regulated in the liver of mice infected with T. b. evansi, which indicated that the inhibition of proliferation of hepatocytes in mice infected with T. b. evansi might be more severe than that in T. b. brucei infection; and (3) more hepatocyte apoptosis occurred in the mice infected with T. b. evansi and this might be probably the most important reason why mice died sooner than those infected with T. b. brucei. Studies of the changes in the gene expression profile in the liver and spleen of mice infected with T. b. brucei may be helpful in understanding the mechanisms of pathogenesis in Nagana disease at the molecular level. By comparing the gene profiles of the liver and spleen of mice infected with T. b. brucei with T. b. evansi, we have identified a number of factors that could explain the differences in pathogenesis in mice infected with these two African trypanosomes.