黄瓜叶片胞间隙几丁质酶与抗霜霉菌侵染关系的研究

采用高抗霜霉病的‘津春4号’和易感霜霉病的‘长春密刺’黄瓜的温室穴盘幼苗为材料,研究了接种霜霉菌对黄瓜叶片胞间隙几丁质酶累积变化及幼苗生长的影响.结果显示:(1)与易感品种相比,抗病品种叶片胞间隙液蛋白浓度升高快、含量高；同时几丁质酶活性上升的速度快、幅度大,于接种后第2天达到峰值,且高活性维持至第7天；(2) SDS-PAGE电泳分析发现,抗病品种有一种27 kD的酸性几丁质酶在接种后第2天迅速积累,并在接种后第4、7天呈现出较高的表达量；Western blotting的结果也证实了上述胞间隙几丁质酶积累的变化.(3)与未接种对照相比,接种处理后第4、7天,易感黄瓜幼苗鲜重、干物质积累量均出现显著降低,但在接种后第7天抗病品种的上述生长指标要显著高于易感病品种.研究表明,接种霜霉菌后,抗病黄瓜叶片胞间隙几丁质酶迅速累积且活性快速升高,以减轻霜霉病对幼苗生长的侵害,这可能是黄瓜抗霜霉菌侵染的一种防御机制.

Relationship between Induced Chitinase in Intercellular Fluids of Cucumber Leaves and Resistance to Pseudoperonospora cubensis

After inoculating with Pseudoperonospora cubensis,the accumulation of induced chitinase in intercellular fluids of plug cucumber seedling leaves of the resistant variety(Cucumis sativus cv.Jinchun No.4) and the susceptible variety(cv.Changchunmici) and the seedling growth of both varieties in greenhouse were studied.As shown by the results,after the inoculation,the content of soluble protein in the resistant cucumber variety rapidly accumulated and reach to higher level than that in the susceptible variety.The activity of chitinase in the resistant variety had a rapid change,leading a peak at the second day,and maintained at high levels until 7 days;the evident expression of a 27 kD acid chitinase was found at the second day by SDS-PAGE method,and had showed visible expressions at the fourth and seventh day.This was further confirmed by western blotting.In addition,compared with CK,the fresh weight and accumulation of dry matter of the susceptible cucumber variety were significantly decreased at the fourth and seventh day after the inoculation.But those indexes of the resistant variety were much more than the susceptible at the seventh day.The above results indicated that the rapid accumulation and fast increasing activity of chitinase in intercellular fluids of the resistant cucumber leaves after the inoculation could reduce the damage of downy mildew to cucumber seedlings.The induction of chitinase was likely as a part of cucumber defense strategy to against P.cubensis infection.