| As one of the most important food crops in world,rice production has significant implications for national food security.Rice is mainly attacked by insect pests such as striped stem borer(Chilo suppressalis walker),rice leaf folder(Cnaphalocrocis medinalis Guenee)and brown planthopper(Nilaparvata lugens Stal).The control of rice insect pests mostly depends on use of insecticides.The long-term unreasonable use of pesticides has led to environmental problems such as reduced sensitivity of insect pests to chemicals,environmental pollution and inseciticide residues in grain.Therefore,finding effective and safe control measures against pests is the most important challenge that needs to be solved urgently.Plant genetic engineering provides a novel approach for the comprehensive prevention and control of rice pests.The and genes have been shown to suppress the feeding and digestion of insect pests of maize.Studies on the Toxin gene showed that the Toxin gene has the effect of inactivating the ribosome,but there was no reported on the role of these genes in rice resistance to insect pests.Hence,we explored the NCBI database and found that RIPI,RIP2 and Toxin genes were located in rice.However it is not clear whether these genes are also resistant to insects in rice.In order to clarify whether these genes have also the function of resistance to insect in rice,we conducted a series of experiments in lab.The main results were summarized as follows:1.Expression of RIP and Toxin genes in different rice varietiesThe expression levels of RIPI,RIP2 and Toxin in the leaves of 10 different rice varieties(TNI、Xiushuil34、Zhejing99、Zhongzao39、Jinzao47、Zhongzheyou8、Y Liangyou689、Yongyou12、Yongyou15 and Yongyoul540)at the tillering stage were determined by Real-Time PCR.The results showed that the expression levels of these three genes in Zhongzheyou 8 were higher than the other 9 rice varieties.2.Expression of RIP and Toxin genes in different growth stages of riceThe expression levels of the three genes in leaves and stems of rice during different growth stages(seedling stage,tillering stage,and milky stage)were measured.The results showed that the expression levels of the three genes in rice seedlings displayed a low level.RIP1 gene and Toxin gene were more abundant in tillering stage than in milky stage.RIP2 gene was expressed in tillering stage and milky stage.The gene expression level in milky stage was slightly higher than that in tillering stage.In the same growth period of rice,the gene expression levels of three genes in leaves were higher than those in stems,which were related to the location of related proteins.The specific reason still requires for analysis of detailed experiments and observations.3.The expression of RIP and Toxin genes after Cnaphalocrocis medinalis feeding on riceThe expression of three genes in rice leaves and stems was determined after C medinalis had harmed rice leaves for different days.The results showed that the expression of RIP1 gene in Zhongzheyou 8 was up-regulated over time.The expression of RIP2 gene was up-regulated in leaves and stems.The Toxin gene had the highest expression level in the 5 d stems.4.The expression of RIP and Toxin genes after Chilo suppressalis feeding on riceThe expression of three genes in rice leaves and stems was determined after C.suppressalis had harmed rice.The expression level of RIP1 gene in rice stems of Zhongzheyou 8 was down-regulated over time.The expression of RIP2 gene in stem was down-regulated over time,and the expression level of RIP2 was up-regulated over time.The expression of Toxin gene in the stem was up-regulated over time.The expression level of Toxin gene in the leaves was higher on the 5 d than on the 1 d and 3 d.5.The expression of RIP and Toxin genes after Nilaparvata lugens feeding on riceAfter N.lugens damages rice,the expression levels of the three genes in the stems ofZhongzheyou 8 were all decreased with time.The expression levels of RIP1 and Toxin genes in the leaves were higher on the 5 d than on the 1 d and 3 d.The expression level of RIP2 in leaves was down-regulated over time.Overall,after feeding by three above insect pests on rice,the expression of RIP andToxin genes showned that both C.suppressalis and C.medinalis larvae have chewing mouthparts,but the damage parts by this two insect species are different(C.medinalis feeding on leaves,C suppressalis boring stems),resulting certain differences in the expression of the target genes that caused by feeding of larvae on rice.Comparing between C.suppressalis and N.lugens,both insects feed on the stem position of the rice,but the mouthparts of the two insects were different(C.suppressalis larvae chewing type,N.lugens sucking type).The results indicated that the RIP gene was down-regulated with time after being damaged,but the expression of Toxin gene in stem was different.The specific reason and mechanism of these differenee need to be further analyzed.Those results can provide breeders with the direction of futher research on resistant rice. |
