低磷诱导水稻化感抑草能力增强的分子生理特性

Molecular Physiological Properties of the Enhanced Weed-suppression Ability of Rice Allelopathy Induced by Lower Phosphorus Supplies

以化感水稻PI312777和非化感水稻Lemont为供体,以无芒稗(Echinochloa crusgalli L.)为受体,采用水培的方法研究低磷(P,0.5mg L-1)胁迫下稻/稗共培体系中水稻化感抑草作用的分子生理机制.结果表明,低磷条件下,化感水稻PI312777抑草效应增强,对稗草的保护酶活性及其它生理生化指标呈明显的抑制作用.进一步分析发现,低磷条件下,化感水稻PI312777根和叶组织中苯丙氨酸解氨酶活性及总酚含量上升,且明显高于非化感水稻Lemont.对水稻根系分泌物中酚类物质的HPLC分析结果表明,低磷条件下,从化感水稻PI312777根系分泌物中检出的酚酸类物质总量是正常磷素条件下的2.89倍,而非化感水稻Lemont中的则是正常磷素条件下的1.17倍.两个水稻品种根部和叶部酚酸代谢途径关键酶基因的差异表达分析结果表明,化感水稻PI312777酚酸代谢途径的4个关键酶基因均上调表达,而非化感水稻Lemont中只有苯丙氨酸解氨酶基因上调,其余均下调.可见,低磷条件下,化感水稻PI312777化感抑草能力增强与其酚酸代谢途径关键酶基因增强表达,代谢途径旺盛,进而导致酚酸类物质含量增加有关.

In order to explore the changing mechanism of rice allelopathic potential under lower phosphorus supplies, allelopathic rice PI312777 and non-allelopathic rice Lemont were employed as donor plants, and the morphological and physiobiochemical characteristics of receiver plant branyard grass （Echinochloa crusgalli） mediated by the two donor plants were investigated under lower phosphorus supplies [0.5 mg （P） L^-1, denoted as P-） and normal phosphorus [6 mg （P） L^-1, denoted as P^＋]. Simultaneously, the content of phenolics and activity of phenylalanine ammonia-lyase in the two rice accessions were detected. Furthermore, differential expression of 4 genes encoding the key enzymes involved in phenolic metabolic pathway was also detected in rice by Real Time Fluorescent Quantitative PCR （FQ-PCR） to evaluate the expression changes in the two rice accessions under lower phosphorus supplies. The results showed that under lower phosphorus supplies, the two rice accessions inhibited the growth of barnyard grass to different extents. The inhibitory effect （IR, %） of allelopathic rice PI312777 on barnyard grass was greatly higher than that of non allelopathic rice Lemont, showing 56.51% （IR, the same below） vs 8.59% in the suppression of root length of barnyard grass, 38.49% vs 5.59% in plant height, and 40.21% vs 4.24% in dry weight. Under lower phosphorus condition, the contents of MDA, soluble carbohydrate and soluble protein, the activities of superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT）, and root activity of barnyard grass were decreased at a higher rate by allelopathic rice PI312777 than those by non-allelopathic rice Lemont. Furthermore, the content of phenolics and activity of phenylalanine ammonia-lyase in allelopathic rice PI312777 were also significantly enhanced compared with those in non-allelopathic rice. The result from the analysis of phenolic acids in the two rice root exudates by using HPLC showed that the total amount of ten phenolic acids concerned in allelopathic rice PI312777 under lower phosphorus supplies was 2,89 times as high as that under normal phosphorus condition. However, it was only 1.17 times in non allelopathic rice Lemont under the same condition. Simultaneously, the expressions of the genes encoded phenylalanine ammonia-lyase, cinnamate- 4-hydroxylase, hydroxylase, and O-methyltransferases, which are the key enzymes involved in phenolic acid metabolic pathway, were all up-regulated in the roots and leaves of allelopathic rice PI312777 under lower phosphorus supplies. But all these enzymes were down-regulated in non-allelopathic rice Lemont except phenylalanine ammonia-lyase in the leaves under the same condition. The results suggested that enhancement of rice allelopathic potential in the suppression of the target weeds under lower phosphorus supplies might be attributed to the up-regulation of the key enzymes involved in phenolic acid metabolism, which led to the activation of phenolic metabolism, and increased phenolic allelochemicals and consequently inhibited the growth of barnyard grass.