The Signal Transduction Pathway Of Oligosaccharide-induced Resistance In Sunflower Against The Rust

It has been confirmed that oligosaccharides can induce the resistance in sunflower against the rust, but the study of signal transduction pathways still not be gone into details. In this study, the germination and penetration of Puccinia helianthi Schw. and the ratio of closed stomata were observed after oligosaccharides induced. The signal transduction pathway of oligosaccharide-induced resistance in sunflower against the rust was known by determining the LOX activity, SA level and callose deposition in sunflower leaves, and by positioning the hydrogen peroxide, as well as the expression of PR5 and PDF1.2 which are the marker genes of SA and JA. The results showed that:1. The urediniospore germination of Puccinia helianthi Schw. was inhibited after the sunflower leaves were treated by oligosaccharide. The germination rates after 1 d and 4 d treated by oligosaccharide were 53.7% and 57.68% respectively. Comparing with the control group, the rate reduced 36.56% and 32.58% respectively. The germination rate after the twice oligosaccharides treatment was 60.44%. Comparing with the control group, it reduced 29.82%.2. The penetration of Puccinia helianthi Schw. was inhibited after the sunflower seedlings were treated by oligosaccharide. 12 h after inoculation, the penetration rate was 26.04% treated with oligosaccharides, the rate is 67.13% in control group, and it had been in a lower level until 72 h. It was significantly lower than the control.3. After sunflower leaves were treated by oligosaccharide, the stomatal closure of leaves increased. The stomatal closure rates of the control group were 24.1% to 50.5%, and the rates of observed group were 79% to 93.4%,significantly higher than the control group.4. 12 h after inoculation, the phenolics was sedimented at the contact sites on sunflower leaves treated by oligosaccharide, the rate was 74.97%, and the rate was 14.01% in contral group; 24 h after inoculation, 46.72% of the contact sites on sunflower leaves treated by oligosaccharide appeared phenolics accumulation, it was 10.98% in control group; 48 h after inoculation, the phenolics was sedimented at the contact sites on sunflower leaves treated by oligosaccharide, the rate was 11.32%, there was no significant difference with the control group.5. The LOX activity decreased after oligosaccharide treatment. The LOX activity was 1.305 U/g·FW·min in control group, and 1.041 U/g·FW·min in treated leaves by oligosaccharide, and 1.295 U/g·FW·min in the leaves when spores were applied after oligosaccharides treatment.6. Oligosaccharide would promote the accumulation of SA leaves when spores penetrated. The SA levels of leaves non-inoculated and inoculated with spores were 17.525ng/g and 17.769 ng/g respectively after oligosaccharide treatment, significantly higher than those of leaves treated by water 17.297 ng/g and 17.526 ng/g respectively.7. When spores penetrated, the callose deposition was sedimented on sunflower leaves. 4 d after inoculation, a little callose deposition was sedimented on sunflower leaves treated by JA and water,a large number of callose deposition at infection sites on leaves treated by oligosaccharide and SA。8. Oligosaccharide could induce expression of PR5 and PDF1.2, it explained that the signal transduction pathway of oligosaccharide-induced resistance in sunflower against the rust was related to SA and JA pathway.The results showed that oligosaccharide could inhibit the infection of Puccinia helianthi Schw.. And the results proved that the signal transduction pathway of oligosaccharide-induced resistance in sunflower against the rust was SA pathway, through the detection of SA level, callose deposition, LOX activity and the expression of PR5 which is the marker genes of SA pathway.