Saijin Wei

Objective Paclitaxel has a broad-spectrum anticancer effect，but its content in Taxus is extremely low，which was unable to meet the growing clinical needs.At present，Taxus suspension cell culture technology is considered to be one of the effective ways to solve the scarcity of paclitaxel.However，cells are prone to genetic variation after continuous passage，resulting in poor cell growth and decreased ability to synthesize paclitaxel.To solve this problem，this study proposes an optimized method for cryopreservation of Taxus wallichiana var. mairei suspension cells. Method The effects of preculture temperature，preculture time，pretreatment agent，dehydration time，cryoprotectant and thawing temperature on cell survival were investigated by single factor experiment with Taxus wallichiana var. mairei suspension cells as materials.On this basis，the response surface optimization of cryopreservation conditions was conducted with cell survival rate as the optimization objective. Result According to the single factor test，three significant influencing factors were selected，which were sucrose concentration，dehydration time and thawing temperature.By response surface optimization，the optimal preservation conditions of cells were obtained.Taxus wallichiana var. mairei suspension cells were first precultured in B5 medium for 12 days at a preculture temperature of 5 ℃，then pretreated with 6.6% sucrose for 30 min at room temperature，removed the pretreatment agent，added 20% ethylene glycol + 35% glycerol + 10% dimethyl sulfoxide + 10% sorbitol as cryoprotectant，dehydrated at 0 ℃ for 31 min，iced at 0 ℃ for 30 min，placed at -20 ℃ for 2 h，and finally placed in a refrigerator at -80 ℃ for 14 days.The frozen suspension cells were rapidly thawed in a water bath at 41 ℃ for 60 s，and then washed with B5 medium containing 1.2 mol/L sucrose to remove the protective agent.Finally，the suspension cells were resuscitated on B5 medium.The survival rate of Taxus wallichiana var. mairei suspension cells after the above cryopreservation treatment could reach 68.19%. Conclusion In this study，the cryopreservation system of Taxus wallichiana var. mairei suspension cells was established and optimized，and a certain cryopreservation effect was achieved，which provided a technical reference for the long-term maintenance of Taxus wallichiana var.mairei and other medicinal plant cells.

Streptomyces JD211 induces rice resistance and reduces the disease index of rice blast. However, the key pathways or components involved in the defense mechanism by which antagonistic microorganisms cause resistance have not been elucidated. To better understand the cellular process involved in JD211-induced resistance, the changes of proteomics in the rice treated with JD211 and Magnaporthe oryzae were investigated. Most proteins associated with porphyrin and chlorophyll biosynthesis decreased in M. oryzae-infected rice, whereas these proteins increased in the rice treated with JD211. Proteins increased by JD211 were also involved in the phenylpropanoid pathway, signal transduction, and ascorbate biosynthesis. These results indicated that JD211 could protect rice from M. oryzae damages by promoting signal transduction and inducing the production of phenylpropanoids. JD211 contributed to energy synthesis for defense responses in plants, reduced the damage of M. oryzae, and improved the rice resistance by inducing an array of defense responses more quickly and efficiently in the rice. The obtained data provide not only important information for understanding the molecular mechanism involved in JD211-induced resistance but also application clues for genetic breeding of crops with the improved M. oryzae resistance.

The induced resistance against plant pathogens via biocontrol agents is considered as an eco‐friendly and promising strategy. In this study, the induced resistance against Magnaporthe oryzae (M. oryzae) in rice seedling by a new potential biocontrol agent Streptomyces JD211 (JD211) was evaluated. The effects of JD211 on defense‐related enzymes activities and defense genes expression were investigated. The biocontrol efficacy of different JD211 concentrations was different, and the treatment of 10 g kg⁻¹ JD211 achieved the highest biocontrol efficacy. Activities of catalase, phenylalanine ammonia‐lyase (PAL) and β‐1,3‐glucanase significantly increased in the presence of JD211. The gene expression level of both PAL and pathogenesis related protein 1 increased when rice seedlings were inoculated with JD211 alone or co‐inoculated with M. oryzae, and the expression level of chitinase gene was enhanced by JD211 in the later stage. All results suggested that JD211 could increase the rice resistance by stimulating a series of defense responses, which was the result of induced systemic resistance by JD211. This work will provide a new biocontrol agent against Magnaporthe oryzae in rice seedling.

通过旱育秧的方式进行水稻育秧，测定秧苗根系和叶片电导率、叶绿素、丙二醛（MDA）及抗氧化酶的变化，研究稻田土（S）、自然堆沤稻草＋稻田土（SS）、加复合腐解菌剂堆沤稻草＋稻田土（SMS）3种育秧基质对水稻生长和抗性的影响. 结果发现：在20 d时，SMS处理组电导率最大，为41.2（± 0.3）μS/cm，叶片MDA含量是S处理组的1.93倍，叶片多酚氧化酶（PPO）酶活比S、SS处理组分别提高了56.15%、8.96%，根系过氧化物酶（POD）酶活比S、SS处理分别提高了226.04%、63.16%，根系苯丙氨酸解氨酶（PAL）酶活为178.79（± 4.02）U g-1 min-1；40 d时，SMS处理组的根系和叶片PAL酶活比S处理组分别提高了135.28%和148.32%. 因此，加复合腐解菌剂堆沤稻草作为育秧基质促进了秧苗生长，显著提高了秧苗的抗性. （图2 表1 参21）

Antifungalmycin 702, a novel polyene macrolide antibiotic produced by Streptomyces padanus JAU4234, strongly inhibited mycelial growth of the rice blast fungus, Magnaporthe grisea, with EC₅₀ of 37 μg/ml and EC₉₀ of 136 μg/ml. Significant reduction in the number of conidia was observed at above 20 μg/ml. Conidia germination and appressorium formation were also suppressed and were not viable with >40 μg/ml. When treated with antifungalmycin 702, hyphae morphology became irregular. Based on microscopic examination, antifungalmycin 702 may exert its antifungal activity by changing the structure of cell membranes and the cytoskeleton and interacting with the organelles. Antifungalmycin 702 thus has potential as a new fungicide in the treatment of rice blast disease.

To explore the practical application value and action mechanisms of Ag-antibiotic 702 against pathogenic fungi, the inhibition spectrum of Ag-antibiotic 702 was studied by measuring the mycelium growth rate of pathogenic fungi, and the effects of Ag-antibiotic 702 on the membrane permeability of Rhizoctonia solani, a typical pathogenic fungus, were investigated, with the variations of mycelium electrolyte leakage and protein, nucleic acid, and Mg2+ and K+ contents under the action of Ag-antibiotic 702 determined, and the effects of Ag-antibiotic 702 on the cell membrane ergosterol biosynthesis and ultramicrostructure observed. The results showed that the active products of Ag-antibiotic 702 had stronger inhibition effect on 13 test pathogens, among which, Sclerotinia sclerotiorum was most sensitive, with the EC50 being 0.23 microg x mL(-1). As compared with the control, the relative electric conductivity of R. solani treated with Ag-antibiotic 702 was increased by 72.2%, the contents of protein, nucleic acid, and Mg2+ and K+ leaked from the R. solani cells were all increased, while the ergosterol content was decreased by 92.0%. The cell membrane outline was not clear, organelles were badly damaged, and vacuole appeared. It was suggested that the inhibition of ergosterol biosynthesis and the increase of membrane permeability could be the main action mechanisms of Ag-antibiotic 702 against pathogenic fungi.

Two polyene macrolide antibiotics: antifungalmycin (1) and fungichromin (2) were isolated from the culture mycelia of Streptomyces padanus 702 via bioactivity-guided fractionation using various chromatographic procedures. Their structures were elucidated on the basis of spectral analysis, and 1 is a new polyene macrolide. Compounds 1 and 2 showed significant inhibition against Gibberella zeae with EC₅₀ values of 26.71 and 2.21 µg/mL, Fusicoccum sp. (plantain head blight) with EC₅₀ values of 23.4 and 3.17 µg/mL, Mucor ssp. 8894 with EC₅₀ values of 28.80 and 2.11 µg/mL, Ustilaginoidea virens with EC₅₀ values of 26.72 and 0.21 µg/mL, respectively. This shows that the microbial secondary metabolites 1 and 2 have the potential to be developed as agricultural fungicides for use against G. zeae, Fusicoccum sp., Mucor ssp. 8894, and U. virens. Open image in new window