Purification, characterization, and heterologous expression of an antifungal protein from the endophytic Bacillus subtilis strain Em7 and its activity against Sclerotinia sclerotiorum.

An antifungal protein exhibiting a high activity against Sclerotinia sclerotiorum in vivo was purified by ammonium sulfate precipitation, hydrophobic chromatography, and gel filtration chromatography from the culture filtrate of the endophytic Bacillus subtilis strain Em7. The protein was characterized as a ß-1,3-1,4-glucanase according to amino acid analysis, and showed excellent properties in thermal stability and acid resistance. At the same time, the antifungal protein was cloned and heterologously expressed in Escherichia coli BL21. The recombinant protein was purified and showed similar enzymatic properties to the native protein, exhibiting strong inhibitory activity against S. sclerotiorum. This shows that the ß-1,3-1,4-glucanase may play a very important role in B. subtilis Em7 biocontrol function. In addition, many physiochemical properties of the native and purified recombinant protein were compared, including the effect of pH, temperature, metal cations, substrate specificity, and kinetic parameters. All parameters were similar between the native and recombinant purified protein, indicating that the purified recombinant protein has potential for industrial applications.

Cloning of flanking sequence in transgenic plants by restriction site-anchored single-primer polymerase chain reaction.

Determining the insertion position of an exogenous gene in the target plant genome is one of the main issues in the transgenic plant field. This study introduced a simple, rapid, and accurate method to clone the flanking sequences of the transgenic bar gene as the anchoring gene in the transgenic maize genome using single-primer polymerase chain reaction (PCR). This method was based on the distribution of restriction sites in the maize genome and adopted the single-primer PCR method. Cloning the flanking sequences with the restriction site-anchored single-primer PCR simplified the experimental procedures by about 70% and reduced the experimental time by more than 80%. In conclusion, the restriction site-anchored single-primer PCR was a simple, rapid method to obtain the unknown flanking sequences in the transgenic plants.

DNA methylation involved in proline accumulation in response to osmotic stress in rice (Oryza sativa).

Proline accumulation is involved in plant osmotic stress tolerance. Given that DNA methylation is related to almost all metabolic processes through regulation of gene expression, we suspected that this epigenetic modification and proline biosynthesis are probably related. To test this, we investigated whether osmotic stress-induced proline accumulation is associated with DNA methylation modifications in rice. We assessed DNA methylation and expression of 3 key genes (P5CR, P5CS, and δ-OAT) involved in proline biosynthesis, and measured proline content under both osmotic stress (15% polyethylene glycol) and control conditions. After osmotic stress, selfed progenies of osmotic-stressed plants accumulated higher concentrations of proline in leaves under both normal conditions and under osmotic stress than the unstressed control plants. Concomitantly, under osmotic stress, the selfed progeny plants showed higher expression levels of P5CS and δ-OAT than the control. This up-regulated expression was stably inherited by the subsequent generation. Methylation-sensitive Southern blotting indicated that 2 of the 3 genes, P5CS and δ-OAT, had greater DNA demethylation in the selfed progenies than in the control. Apparently DNA demethylation facilitated proline accumulation by up-regulating expression of the P5CS and δ-OAT genes in response to osmotic stress.