Use Of Silicon Transporter Mutant To Study Mechanisms Of Synergistic Effect Of Silicon And Salicylic Acid Signaling On Rice Anti-herbovore Resistance

Rice(Oryza sativa L.)is one of the most important grain crops in China.The brown planthopper(Nilaparvata lugens Stal,BPH)(Homoptera:Delphacidae),is one of the most important pests of rice in Asia,causing serious damage of grain security in China.Rice is a typical silicon(Si)accumulator plant.Rice can actively absorb silicon through Lsil transporter.Silicon is absorbed by rice,which has great influence on rice resistance against both biotic and abiotic stressses.Among them,the mechanism of improving rice’s insect resistance is mainly reflected in two aspects,one is physical defense,another is chemical defense.Salicylic acid(SA)is an endogenous defense signaling substance in plants.The SA signaling participates in many physiological and biochemical reactions in plants and plays a key role in plant response to insect attack.In this study,wild-type(WT)and silicon-transporter mutant OsLsil of rice were treated with and without silicon to determine the effects of Si addition on rice resistance and defense responses to the most destructive sucking rice pest BPH.To provide a theoretical basis for the application of silicon fertilizer on agriculture,thus reducing the use of chemical fertilizers and pesticides,ecological security and food security.The main results are as follows:1.First of all,silicon application increased the plant height and had no obvious effect on root length.Silicon addition promoted the accumulation of aboveground material and inhibited the accumulation of underground substances in rice.Silicon application also significantly increased the silicon content of rice stalks.It is suggested that silicon application can change the growth of rice and change the distribution of material in rice.Study on the application effect of silicon on rice brown planthopper resistance,found that silicon can reduce selectivity to host the brown planthopper,reduce the amount of honeydew of BPH,have obvious effect on the fecundity of Brown Planthopper and hatching number,silicon fertilizer can also reduce the number of rice plants on survival of brown planthopper,rice brown in silicon planthoppers were also showed a stronger vitality.All of the above proved that silicon application could improve the resistance of rice to brown planthopper.2.Secondly,activities of three oxidases of superoxide dismutase(SOD),peroxidase(POD)and polyphenol oxidase(PPO)in rice plants were enhanced by silicon application.On one hand,enzymes play an important role in sucking insect induced plant defense response,the other side also shows that silicon can induce significant changes in rice enzymes,help plant more rapid response defense system infection and identification of ROS signal molecules and activate the corresponding brown planthopper,thereby improving insect resistance.The activity of phenylalanine ammonia lyase(PAL)was also enhanced by silicon application.At the same time,the content of soluble sugar and amino acid in rice treated with silicon did not change significantly,and silicon application did not improve insect resistance by changing the nutritional status of rice.3.Finally,it is found that SA and BPH can enhance the silicon content in rice,indicating that silicon plays an important role in rice resistance to stress,and SA is closely related to Si.It is found that silicon can induce the increase of rice SA in insect pests,indicating that silicon enhances insect resistance and SA pathway.Silicon involved in rice insect resistance is regulated by the way of SA elevation,and again confirms the correlation between Si and SA.Then it was found that both silicon addition and spraying SA could reduce the intake of brown planthopper.Both silicon and SA were better than silicon alone and SA alone.It is further proved that Si is also interacted with SA,that is,to cooperate with each other against BPH.After that,it was found that the expression of OsICS1 and OsPAL4,a key gene of SA synthesis pathway,is related to silicon in rice pests.That is to say,adding silicon can enhance the expression of these two genes,and verifies the fact that SA increases more seriously when insects are added to silicon.In addition,the expression of JA and ET related genes was not significantly influenced by silicon under the stress of brown planthopper.The expression of OsCPSl gene by GA was affected by silicon,indicating that GA pathway might also play an important role in the resistance of silicon to insects.It can be seen that the resistance of silicon to rice is not only related to SA,but may also be related to other ways.In addition,silicon application could induce the expression of anti-BPH gene BPH3 in rice,indicating that silicon can regulate the expression of rice anti-BPH genes to resist insect pests.