Gene Expressions And Physiological Effects Induced By Wheat Powdery Mildew Pathogen In Powdery Mildew Resistance Strains L693

Wheat (Triticuma aestivum L.) is rich in protein, minerals, fat and starch, which are important food crops grown in our country. Wheat powdery mildew is airborne fungal disease caused by powdery mildew (Blumeria graminis f.sp.Tritici). It mainly harms the blades, but it can be seriously hazards sheath, stem, spike-head, which is one of the important leaf diseases affecting the yield and quality of wheat. In the 1980s, due to the continuous improvement of water and fertilizer conditions, massive planting of susceptible varieties, the increasing seeding density and mutating of pathogenic fungi, lead to the onset of wheat powdery mildew range expanding trend. It gradually spread from the southwest and southeast coastal wheat growing area to almost all wheat growing areas, and in many areas other diseases even have been replaced by wheat powdery mildew diseases.Wheat powdery mildew diseases become the major diseases in these areas.Since Waterhouse(1930) found the powdery mildew resistance gene in wheat variety Thew, scientists from various countries have done much research on the genetic characteristics and chromosome locating of wheat powdery mildew resistance genes.64 main wheat powdery mildew resistance genes have been found in wheat and re(?)ed species so far. They are numbered from Pml to Pm47, covering more than 40 sites.Pm40 was a powdery mildew resistance gene, which was discovered and named from GRY19 and located in 7BS of the wheat. Wheat varieties containing Pm40 gene in are highly resistant to powdery mildew in Henan and Sichuan, and they are immune to all physiological powdery mildew races.In order to elucidate the mechanism of disease resistance genes Pm40, especially gene expression and physiological effects after powdery mildew infectionIn this paper, powdery mildew resistant strains L693 (containing Pm40) and powdery mildew susceptible strains L1095 are used to study the gene resistance mechanism in early infection stages of wheat powdery mildew (0h,24h,48h,72h). Through measuring the photosynthesis parameters and antioxidant enzyme activity and SSH comprehensive analysis, we want to build up a good basis for further cloning of the resistance gene. The results were as follows:1.After comprehensive analysis L693 and L1095 fluorescence data of photosynthesis, the results showed that in the early powdery mildew infection stage, because L1095 is free Pm40 gene, it can only adjust the opening and closing of stomata to resist pathogen invasion; while L693, which contains resistance genes, the resistance genes of it get activated between 0-24 hours. L693 closes parcial PSII system to protect against pathogen invasion PSII reaction center injury between 24-48 hours. The plants re-optimize the PSII system after 72 hours, recovering high photosynthetic capacity to give full play host resistance.2.By analyzing the antioxidant enzyme activity and malondialdehyde (MDA), soluble protein, proline content changes after powdery mildew infection, the results show that L693 was found to have lower antioxidant enzyme activity within 48h, then antioxidant enzyme activity significantly increased in L693 after 48h. Studies have shown that low levels of activity can serve as signaling molecules, so we think that H2O2 in L693 works as a signaling molecule to stimulate the resistance gene expression within 48h, and with the increase in the level of resistance, the host builds resistance after 48h.3.we extract the same amount of mixing RNA of the two materials at 24,48,72 h to build a forward and reverse SSH-cDNA library. L693 was used as tester, L1095 as the driver in forward SSH-cDNA library. The results showed that 48.3% of the genes expressing in L693 participated in the process of carbon metabolism; 15.5% participated in the photosynthetic pathways; 5.2% was involved in nitrogen metabolic pathways; 1.7% metabolic processes involved in the transportation; the function of the remaining 27.6% of the expressed genes is still not clear. Of the genes expressing in L1095,23.1%,19.2%, 3.8%,3.8% of the genes were involved in the photosynthetic metabolism, cell wall metabolism, nitrogen metabolism and carbon metabolism pathway respectively; function of over 50% of the genes is unclear. At the same time, we found a EST sequences JZ532636, which is located on 7BS. After sequencing, a certain homology was found between the EST sequences and encoding3-ketoacyl-CoA synthase 6(E=0, Identity=92.9%).In Arabidopsis, KCS1 gene encoding 3-ketoacyl-CoA synthase involved inthechain extension of the fatty acid, and synthetic waxes. And studies have reported long-chain fatty chain involved in the plant-pathogen interaction in the process of signal transduction, suggesting that this gene may be involved in signal transduction of powdery mildew disease after infection; adding the gene is located on chromosome 7BS, so the gene encoding 3-ketoacyl-CoA synthase 6 may be a candidate gene of Pm40.In summary, this study from the perspective of gene expression, biochemistry and physiology clarifies the Pm40 resistance to powdery mildew infection mechanism: oxidative burst as first signaling molecular when pathogens attacked to actively trigger resistance related gene expression; then genetic regulation of photosynthetic competence by closing part PSII to protect PSII; and finally, plant reopens PSII reaction centers and restores high photosynthetic competence, optimizes energy utilization, and host resistance fully establishes. This study helps to completely clear Pm40 mediated resistance mechanism, but also help to speed up the resistance to powdery mildew resistance ge(?) in the genetic improvement of wheat.