Effects Of Sulfur Nutrition On Interactions Between Rice And PXO99

Rice bacterial blight is a bacterial disease caused by Xanthomonas oryzae pv.Oryzae(Xoo).Bacteria usually invade rice from the water holes or wound and produce gray spots along the veins.Rice suffered from bacterial blight,general reduction of 10%or even worse,is the second largest disease after rice blast.Many sulfur compounds are involved in the process of plant resistance to various diseases and insect pests,and the application of ammonium sulfate at seedling stage can improve the disease resistance of rice seedlings,and it is speculated that the sulfur metabolism of rice is closely related to the disease resistance.Xa21 is a resistance gene of rice bacterial leaf blight,PX099.Avrax21,the non-toxic factor,interacts with Xa21 in rice to induce the resistance to PX099.Here,the disease resistance of rice with two different rice varieties CX621B(transgenic rice transferred with Xa21 gene)and D62B(no Xa21 gene)was analyzed after different sulfur nutrition treatment.The leaves of rice were inoculated with PX099 under different sulfur nutrient treatment.The lesion length of rice leaves was found to reach the highest value at 0.5mM sulfate treatment.In presence of JA or its biosynthesis inbibitor,for CX621B,lesion length at high concentration of sulfate were reduced to t o about 50%of that at 0.5mM,for D621B,lesion length at high concentration of sulfat e were reduced to about 60%of that at 0.5mM.In order to further understand the reasons,the relative transcription level of Xa21 gene were analyzed.The results showed that the expression of Xa21 gene,with the increase of the concentration of sulfur,the relative transcriptional level of Xa21 increased gradually.The GSH content was measured and found to have little correlation to rice disease resistance to PX099.In order to analyze if plant hormone invloved in the disease resistance to PX099,OsJAZ8 and OsRD22 were screened to be positive marker genes for jasmonte(JA)and abscisic acid(ABA)in rice.According to the transcription level of the marker gene,we found that the ABA content of CX621B was much lower than that of D62B under the condition of 3.3mM sulfur concentration,and the difference was not significant except at other sulfur concentration.The relative transcription level of the rice bounded jasmonic acid(OsJAZ8)is higher than that of the D62B,CX621B was 3times,6 times and 3 times higher than that of D62B at 0-0.5mM sulfur concentration.Under the condition of 3.3-1 OmM sulfur concentration,CX621B was 3times,6 times and 5 times higher than that of D62B(Figure 2.7).It was evident that the contents of CX621B and D62B in transgenic rice was close to that at 3.3-5mM,and the content of SA(salicylic acid)10 mM,the difference between the two gradually increased,and showed a downward trend,in lOmM sulfur concentration conditions,the difference between the two reached the maximum,CX621B is D62B 2 times.CX62 1B and D62B lesion length and JA content in the overall level showed a certain correlation,indicating that JA on the PX099 defense plays a key role,and elevated expression of Xa21 in CX621B upon the increase of sulfur concentration in medium,suggests that effects of sulfur nutrition on rice disease resistance were probably achieved via fluctuation of hormone and Xa21 contents in rice leaves.