Fanyu Kong

Synthesis of thiodiazole copper microcapsules and release behavior of inhibiting R. solanacearum

Microcapsules are one of the most useful devices to reduce the dosage of pesticides and prolong the duration of the active ingredient in target crops. In this study, thiadiazole copper (TDC) microcapsules were synthesized by in situ polymerization using poly(urea-formaldehyde) and characterized by field emission scanning electron microscopy, laser diffraction analysis, 3D optical microscopy, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy. The effects of pH and temperature on the release of TDC were characterized by UV-visible absorption spectroscopy. The relationship between the micromechanical behavior of the microcapsules and release of TDC was studied by nanoindentation tests. The particle size distributions of the microcapsules (10–530 μm) were controlled by different reaction parameters. The microcapsules were stable below 220 °C, as determined by TGA. The release kinetics indicated that the higher the temperature, the faster the release rate. The TDC microcapsules were sensitive to pH, and the fastest release rate was observed at pH 4.0. The maximum load, hardness, and Youngs modulus under the same displacement conditions decreased during the release. Water swelling was the major reason for TDC release from the microcapsules. The pot experiments confirmed that the microcapsules exhibited long-term sustained release of TDC, thereby protecting the tobacco from R. solanacearum.

Extract of Syringa oblata: A new biocontrol agent against tobacco bacterial wilt caused by Ralstonia solanacearum.

Ralstonia solanacearum causes serious wilt disease in tobacco. To effectively control this disease, the antibacterial activity of 95% ethanol extracts from the flower buds of Syringa oblata was examined. Based on GC-MS analysis and an inhibition experiment against R. solanacearum, the main antibacterial component is eugenol. We further determined the effect of eugenol on the physiology, biochemistry, and cellular morphology of R. solanacearum. The results showed that eugenol can destroy wilt bacteria, leading to the disappearance of flagella, the leakage of contents, and the appearance of a cavity. SDS-PAGE showed that eugenol decreased protein content in R. solanacearum, reduced medium carbohydrate utilization, and inhibited CAT and SDH activity. The above results showed that eugenol had a significant inhibitory effect on R. solanacearum and this component has the potential to prevent tobacco bacterial wilt.

Cloning, expression analysis and recombinant expression of a gene encoding a polygalacturonase-inhibiting protein from tobacco, Nicotiana tabacum

Polygalacturonase inhibiting proteins (PGIPs) are major defensive proteins produced by plant cell walls that play a crucial role in pathogen resistance by reducing polygalacturonase (PG) activity. In the present study, a novel PGIP gene was isolated from tobacco (Nicotiana tabacum), hereafter referred as NtPGIP. A full-length NtPGIP cDNA of 1,412 bp with a 186 bp 5′-untranslated region (UTR), and 209 bp 3′-UTR was cloned from tobacco, NtPGIP is predicted to encode a protein of 338 amino acids. The NtPGIP sequence from genomic DNA showed no introns and sequence alignments of NtPGIP’s deduced amino acid sequence showed high homology with known PGIPs from other plant species. Moreover, the putative NtPGIP protein was closely clustered with several Solanaceae PGIPs. Further, the expression profile of NtPGIP was examined in tobacco leaves following stimulation with the oomycete Phytophthora nicotianae and other stressors, including salicylic acid (SA), abscisic acid (ABA), salt, and cold treatment. The results showed that all of the treatments up-regulated the expression of NtPGIP at different times. To understand the biochemical activity of NtPGIP gene, a full-length NtPGIP cDNA sequence was subcloned into a pET28a vector and transformed into E. coli BL21 (DE3). Recombinant proteins were successfully induced by 1.0 nmol/L IPTG and the purified proteins effectively inhibited Phytophthora capsici PG activity. The results of this study suggest that NtPGIP may be a new candidate gene with properties that could be exploited in plant breeding.