Stress On Physiological And Biochemical Effects And The Effect Of DNA Methylation Of Soybean

Adversity stress can lead to stress responses and genome-wide variation in plant physiology to escape or endure adversity. As an epigenetic modification phenomenon, the main function of DNA methylation is to regulate gene expression and to maintain the stability of the genome, and it plays an important role in the process of plant abiotic stress response.Cercospora sojina Hara is a worldwide fungal disease, and seriously affect the yield and quality of soybean. Researching the physiological and biochemical characteristics and genomic methylation variation under Cercospora sojina Hara stress has the great significance to reveal the molecular mechanisms of soybean resistanting to Cercospora sojina Hara. This paper selects soybean susceptible strains(Long pin 09-85) and highly resistance strains(Yu nong 09-521) as experimental materials to study Cercospora sojina Hara inoculation treatment on physiological and biochemical effects and the effect of genomic DNA methylation of soybean and to investigate the relationship between DNA methylation and the resistance of Cercospora sojina Hara. The experimental results are as follows:1. After the infection of Cercospora sojina Hara, the leaf disease spot number of Long pin 09-85 was large, and the area of leaf disease spot was 21 percent to 50 percent. It belonged to the level four- susceptible. The leaf disease spot number of Yu nong 09-521 was minimal, and the area of leaf disease spot was less than 1 percent. It belonged to the level one- highly resistance.2. The result of determining soybean physiological and biochemical indexes under Cercospora sojina Hara stress showed that compared with the control, the O2- and MDA content within the plant leaves of the soybean susceptible strains increased, the H2O2 and chlorophyll content decreased, SOD, CAT, APX, POD activity increased, and the rise of that was larger than highly resistant strains. In highly resistant strains, the O2-, H2O2 and MDA content within the leaves decreased, the chlorophyll content increased, and SOD, CAT activity increased, APX, POD activity decreased. These results described that the plasma membrane and chloroplast of the highly resistant plants suffered a minor injury, and they had a very strong resistant property.3. The result of using methylation-sensitive amplification polymorphism(MSAP) technical to analyse soybean genomic DNA methylation levels and patterns of susceptible and resistant strains under Cercospora sojina Hara stress showed that after Cercospora sojina Hara stress treatment, the soybean leaf DNA methylation ratio(Full methylation rate + Semi-methylation rate) of both strains decreased comparing with the control, and the downward trend of the susceptible strains was obvious. The methylation patterns of two kinds of strains in the stress response were based on demethylation, but the difference between methylation variation of highly sense strains and demethylation variation was large, and the difference between methylation variation of highly resistant strains and demethylation variation was small. The methylation polymorphism of highly resistant strains was higher than that of susceptible strains. It was inferred that DNA methylation may play an important role in the resistant response of soybean, and there were differences among different resistant strains.4. The result of methylation differential bands with homology comparisons and functional analysis showed that the DNA methylation mutate range was wide, and differential fragments showed high homology with soybean genome, and most of that were associated with soybean response to adversity stress.