植物毒素茄格孢吡喃酮A的研究(英文)

Study on a Phytotoxin Solanapyrone A

致病真菌Ascochyta rabiei感染鹰嘴豆植物体产生三种植物毒素,茄格孢吡喃酮A,茄格孢吡哺酮B和茄格孢吡喃酮C,其中茄格孢吡喃酮A的毒性最大,往往在感染的植物体中表现出植物体变黄,植物茎部变脆,易折断等病理现象,严重时导致整个植物体因枯萎病而死亡,体外培养Aseochyta rabiei研究已知,该致病菌产生一些叫做茄格孢吡喃酮的植物毒素.当用分离提纯的茄格孢毗喃酮A毒素喂养植物体时虽然出现了与病菌感染植物体完全一样的病理现象,但研究者均不能从感染植物体或者体外喂养毒素的植物体中重新分离到该毒素,很可能这种毒素通过某种机制被鹰嘴豆植物细胞代谢转换成另外一种物质,为了研究这一过程,我们提取鹰嘴豆植物的蛋白质提取物(30%-70%硫氨饱和沉淀法)于实验室条件下分离提取并用HPLC方法鉴定植物毒素茄格孢吡喃酮A反应.不管还原物质NADPH存在或者不存在,发现植物毒素茄格孢吡喃酮A消失,即使在鹰嘴豆蛋白制备物加热沸腾处理后与毒素的反应中也出现植物毒素茄格孢吡喃酮A的大量丢失,说明蛋白质制备物很可能不是酶.HPLC(高压液相色谱)检测反应产物时出现了一个新物质.NMR(核磁共振)确定该物质为脱甲基的茄格孢吡喃酮A.进一步的研究得知,该脱甲基的茄格孢吡喃酮A不是鹰嘴豆植物蛋白质提取物的作用下产生的,而?

Solanapyrone A(solA) ,a toxin produced by the fungus Ascochyta rabiei, casual agent of chickpea blight, is studied in this paper and it is found that solA disappears when the toxin is mixed with the protein extracts of chickpea. A new compound with a longer retention time than the toxin (which elute about 26 minutes withλmax233 nm compared to sol A that elute about 13 minutes with λmax 327 nm) can be detected on reversed phase HPLC(C18 ODS analytical column) when the fractionated 30%-70% ammonium sulphate saturation fractions from chickpea hypocotyls extract incubated with solA. It is clear from the further study by MS (mass spectrometry) and NMR (nuclear magnetic resonance) that the new compound is a demethylated solA and it can be formed by the mixture of ammonium sulphate residue and solA.When the protein fraction is freed from ammonium sulphate by dialysis and Sephadex G-75 column gel filtration and incubated with solA, the new compound was not formed but solA still disappears, and recovery of solA is only 3. 2%-8. 6 %. SDS-page analysis of the active protein fractions showed several protein bands ranged from 100kDa to 40 kDa in the gel. When these protein fractions were separated by FPLC it is discovered that solA, the aromatic aldehyde not only can react with ammonium sulphate, producing new compound, but also can react with Tris-HCL buffer (pH7. 5) and produce another new compound with λmax 321nm which elutes at retention time 19min . The NaCl, the increasing linear gradient in FPLC, can also affect solA to cause some loss of it. When solA is incubated with only NaCl, the loss of solA is about 30%-38%, but no new compound is found. Boiled 30%-70% protein extract also shows high activity towards the solA and the loss of solA was 92%-94%.It can be inferred from the result of the study that solA seems to be a labile compound, it possibly can bind to proteins or lower molecular weight compound non-specifically. This is probably the reason for both its toxicity and failure to find the compound in chickpea plants infected by fungus or fed with the compound.