Oligochitosan inhibits Phytophthora capsici by penetrating the cell membrane and putative binding to intracellular targets

The mechanism of action of oligochitosan, which has shown great antifungal activity against Phytophthora capsiciin vitro, was studied using 2-aminoacridone-labeled oligochitosan (2-AMAC-oligochitosan) and a gel-retardation experiment. Internalization of 2-AMAC-oligochitosan in cysts, germtubes and sporangia of P. capsici was confirmed by confocal laser scan microscopy (CLSM), and the degree of uptake depended on the incubation concentration. 2-AMAC-oligochitosan localized mainly in the cytoplasm and showed no binding to both cell wall and cell membrane. Mannose, an inhibitor for oligochitosan uptake by macrophages, could not inhibit the internalization of oligochitosan in P. capsici. The gel-retardation experiment showed that oligochitosan bound strongly to DNA and RNA of P. capsici. These results indicate that oligochitosan exerts its antifungal activity by penetrating the cell membrane and putative binding to intracellular targets such as DNA and RNA.     

氨基寡糖素田间防治辣椒疫病及体外抑菌试验

研究了氨基寡糖素田间防治辣椒疫病和体外对辣椒疫霉(Phytophthoracapsici)的抑菌作用,为其在生产上的应用提供依据。田间喷雾使用氨基寡糖素对辣椒疫病有一定的防效,40mg/L氨基寡糖素对辣椒疫病的防效高达73.2%。采用生长速率法在马铃薯葡萄糖琼脂(PDA)上研究了氨基寡糖素体外对辣椒疫霉菌丝生长的影响,结果表明氨基寡糖素可以抑制辣椒疫霉的菌丝生长,有效中浓度EC50为100mg/L。在无菌水中氨基寡糖素可以抑制辣椒疫霉新生菌丝上孢子囊的形成以及静止孢的萌发,有效中浓度EC50分别为0.64mg/L和41.84mg/L。     

Induction of antiviral resistance and stimulary effect by oligochitosan in tobacco

Oligochitosan was applied by spraying it on tobacco leaves for inhibition of tobacco mosaic virus (TMV). The maximum inhibition of TMV by oligochitosan was observed when inoculation occurred at 24 h after spraying 50 μg ml⁻¹ oligochitosan. The production of H₂O₂ and NO in epidermal tobacco cells induced by oligochitosan was investigated by epidermal strip bioassay and LSCM, using cell permeable fluorophore diaminofluorescein diacetate (DAF-2D) and 2′,7′-dichlorofluorescin diacetate (H₂DCF-DA), respectively. Epidermal tobacco cells treated with oligochitosan resulted in a strong increase of intracellular NO and H₂O₂. Oligochitosan and NO donor sodium nitroprusside (SNP) induced the defense reaction against tobacco mosaic virus (TMV), and increased phenylalanine ammonia-lyase (PAL) activity. Co-treatment of the tobacco cells with oligochitosan and NO scavenger CPTIO blocked the inducing resistance. The results indicated that the defense response induced by oligochitosan was connected with NO pathway.     

壳寡糖与草莓细胞结合过程的研究

 壳寡糖是一类能有效的诱导植物抗病性的重要激发子。本研究用2 - 氨基吖啶酮(22AMAC)标记壳寡糖, 应用激光共聚焦显微成像技术, 研究了壳寡糖与草莓细胞结合过程。结果表明壳寡糖能通过草莓细胞壁与细胞膜结合, 在细胞壁和细胞膜上有其结合位点, 与壳寡糖的结合具有专一性。     

氨基寡糖素诱导作物抗病毒病药效试验

总结了氨基寡糖素防治烟草、辣椒及番茄3种作物病毒病的田间实验结果,为其在生产上的应用提供依据。实验结果表明氨基寡糖防治烟草病毒病防效高达77.9%,辣椒病毒病防效77.0%,番茄病毒病防效74.45%,喷雾使用,浓度为稀释300~400倍。     

Oligochitosan induces cell death and hydrogen peroxide accumulation in tobacco suspension cells

Oligochitosan has been shown to induce several plant defense responses. In the present work, the effect of oligochitosan on tobacco cell survival was investigated. The results showed that oligochitosan caused tobacco cell death in a dose-dependent manner. About 40.6 % tobacco cells died when cultured for 72 h after 500 μg ml⁻¹ oligochitosan treatment. Certain aspects of this cell death process appeared to be similar to apoptosis in animal cells. These included shrinkage of cytoplasm and condensation of chromatin. Oligochitosan also induced H₂O₂ accumulation in tobacco cell suspension culture. The role of H₂O₂ in the signal transduction that leads to cell death was investigated. Co-treatment of tobacco cells with oligochitosan and catalase inhibited H₂O₂ accumulation but did not inhibit the induction of cell death. The results suggested that apoptosis-like cell death of tobacco cells induced by oligochitosan is independent of H₂O₂ signal pathway.     

Effect of foliar application of oligochitosan with different molecular weight on growth promotion and fruit yield enhancement of chili plant

Oligochitosan (OC) is effective biostimulant on growth promotion and elicitation against disease infection for plants. However, the range of OC molecular weight that exhibits the most effective activity is not fully understood and requires further investigation. In this study, OCs with different weight average molecular weight (Mw) were prepared by gamma Co-60 irradiation degradation of chitosan in solution and the effect on growth promotion and enhancement of fruit yield of chili plant (Capsicum frutescens L.) by foliar application of OCs particularly with Mw of 7.8, 5.0, and 2.5 kDa was investigated. Chili plants, cultivated in a greenhouse were sprayed with OC concentration of 50 mg/L for three times. Results indicated that among treatments, OC with 2.5 kDa proved to be the best, which increased the shoot fresh weight by 71.5%, shoot dry weight by 184%, total chlorophyll content by 12%, and fruit fresh weight by 49.8% for the control. Thus, OC with low Mw (2.5 kDa) that can be suitably produced on large scale by gamma Co-60 ray irradiation degradation of chitosan solution is potentially promising to apply as a biostimulant to enhance chili fruit yield significantly.     

受壳寡糖诱导的油菜MAPK基因的克隆与分析

利用油菜cDNA芯片差异显示得到一个可被壳寡糖诱导的, 与已知植物丝裂原活化蛋白激酶(MAPK)同源性高达94%的cDNA片段, 利用cDNA末端快速扩增(RACE)的方法得到了该片段全长, 与拟南芥中AtMPK4具有高同源性, 故将其命名为BnMPK4登录到NCBI GenBank(DQ206628)。用生物信息学方法分析, 该基因属于植物MAPK的B家族, 具有植物MAPK典型的TXY保守区域, 在C端也含有一个在B家族中保守的CD区。利用半定量RT-PCR检测发现BnMPK4在叶片中表达且可被茉莉酸(JA)和壳寡糖诱导, 但对水杨酸(SA)和脱落酸(ABA)响应不明显。推测该基因在壳寡糖诱抗信号转导和JA/ET信号通路中起关键作用。     

壳寡糖改善珍珠龙胆石斑鱼非特异性免疫能力的机制

为研究壳寡糖(OCS)对珍珠龙胆石斑鱼非特异性免疫能力的影响及作用机制,实验通过在基础实验饲料中分别添加0(对照组)、200、400和800 mg/kg的壳寡糖投喂珍珠龙胆石斑鱼4周,综合分析壳寡糖对石斑鱼免疫调控作用的影响.实验首先检测了壳寡糖对鱼体内免疫及抗菌相关酶活性的影响.结果 显示,投喂壳寡糖后显著提高珍珠龙...     

壳寡糖提高茄子幼苗抗冷性的效应研究

分别以1/1 500、1/1 000、1/500 和1/100(w/v)4种浓度的壳寡糖溶液对4片真叶期茄子幼苗进行叶面喷施,研究壳寡糖对茄苗抗冷性的影响.结果表明:除1/100浓度外,其它浓度壳寡糖喷施的幼苗经5℃低温胁迫处理3 d后,与清水对照组相比,其低温伤害率减少,常温下恢复生长后的存活率提高;叶片相对电导率和MDA含量增幅较小,可溶性糖和脯氨酸含量升高;SOD和POD活性增大,CAT活性降幅减少.因此,适宜浓度壳寡糖处理可增强茄苗的抗冷性, 且以1/1 000壳寡糖处理的抗冷效果最明显.