Studies On Synthesis And Regulation Of Lignin In Wheat Leaves Of Slow Stripe Rusting Varieties Inoculated By Puccinia Striiformis F.sp. Tritici

Wheat stripe rust is caused by the basidiomycetous fungus Puccinia striiformis f.sp. tritici and is the most destructive disease of wheat. Due to the high single-gene controlled of anti-resistance wheat varieties in the production is easily to breakdown, the minor-genes controlling durable-resistance species were more and more be attention. Wheat slow rust is controlled by minor genes, and its reaction type is sensitivity. However, compared with the susceptible varieties, slow rusting shows a longer incubation period, smaller colonies, slower expansion, the smaller number of urediniospores of pathogen, lower severity degree, and so on. The characteristics of slow rusting have a great significance to maintain the stability and durability of resistance. Lignin and plant disease resistance have a great mutuality, and cell wall lignification is an important mechanism to wheat slow rusting. Caffeic acid O-methyltransferase (COMT) is an enzyme of lignin biosynthesis, its expression increased has a positive meaning to the synthesis of lignin.In this paper, the slow rusting of wheat varieties Chuanmai 107 and funo, highly resistant variety Chuanmai 42 and susceptible varieties Chuanmai28 and Taichuang29 were direct for research subjects. Respectively, From the cell structure, chemical composition and the level of gene expression of wheat varieties, the lignin content and the expression level were studied, after inoculated with severe isolate of wheat stripe rust: CY32. We used free-hand sections and toluidine blue staining method from the histological observation of the level of the leaves of the tested cultivars the degree of cell wall lignification; used thioglycolic acid test for the determination of lignin content in leaves of species; and used real-time quantitative fluorescence PCR (RT-PCR) method for relative expression analysis of COMT.The experimental results show that using free-hand sections and observed under an optical microscope methods, we can see that the cell wall of wheat leaves inoculated by CY32 were stained with toluidine blue O on blue, but can not determine the extent of leaf cell wall lignification. It shows that this method applies only to the characterization of plant cell wall lignification determine, and can not be used for quantitative analysis of the degree of lignification. Thioglycolic acid method with lignin content determination showed that lignin content in leaves of Chuanmai 42, Funo and Chuanmai 107 after inoculation for 7 and 14 days, the control rate of increase was significantly higher than susceptible varieties Chuanmai28 and Taichuang29. So in the test for high resistance and slow rusting wheat varieties, against the highly pathogenic stripe rust lignin content resulted in a significant increase, and susceptible wheat varieties of no significant changes in lignin content. High resistance to slow rust-resistant varieties of both mechanisms plays an important role. Through the method of RT-PCR relative to the COMT gene expression analysis showed that, the COMT gene expression in leaves of Chuanmai42 and Funo after inoculation for 7 days was significantly higher than control, with the results of determination of lignin content is consistent. Prove that the expression of COMT in these two varieties 7 days after inoculation is correlated with lignin synthesis. In Chuanmai 107, Taichuang29 and Chuanmai28, the COMT gene expressions are no significant difference between the controls and inoculation. Might be because in Chuanmai 107 the enzyme regulating the lignin synthesis is not COMT, or COMT in the 7 days ago against a large number of expressions. 14 days after inoculation of the test varieties for COMT gene expression in leaves are also no significant difference between the controls, indicate the possibility of the impact of disease in the period of the expression of lignin has been the peak period.Through the experiments, we studied the wheat stripe rust on the impact of lignin content, and lignin content of lignin synthesis COMT regulation, further understanding of the mechanisms of wheat slow stripe rusting, provide a theoretical basis to wheat breeding work. This study also can be referred as a reference to plant resistance mechanisms and gene expression research of other cereal crops.