The Function And Mechanism Of OsmiR1858a In Rice Resistance To Bacterial Blight

Rice(Oryza sativa)is one of the world's most important food crops,raising more than one third of the world's population.Bacterial blight caused by Xanthomonas oryzae pv.oryzae,which belongs to a kind of yellow mutant bacterium,is one of the most devastating and widespread bacterial diseases of rice.The exploration of related resistance mechanism has become a key step to cultivate the rice resistance to bacterial blight.microRNAs are a kind of widespread in plant body,endogenous,non-coding short(21-24 bp)small RNA molecules,mainly mediated in post-transcriptional level regulation gene function.A large number of studies confirmed that microRNAs are not only important for plant growth and development,but also as key regulators in plant responses to biotic and abiotic stresses.Preliminary laboratory experiments results showed that OsmiR1858a was highly up-regulated significantly after inoculation with bacterial blight,which may be involved in rice bacterial blight and screened OsHEN1 were OsmiR1858a target gene.OsHIN1 over-expression vector,OsHIN1 synonymous mutant over-expression vector,pre-OsmiR1858a over-expression vector,interference with OsmiR1858a STTM vector and promoter + GUS vector were constructed.In this paper,we will use the obtained transgenic materials to further study the function and mechanism of OsmiR1858a.The results are as follows:(1)T1 generation were screened by Hyg,the results show that each transgenic rice at least four strains are a single copy.The expression test showed that expression of OsHIN1 was negatively correlated with the expression of OsmiR1858a.However,OsHIN1 synonymous mutations over-expressing lines did not.It is indicated that OsmiR1858a is silencing OsHIN1 in a shearing manner,whereas OsHIN1 synonymous mutation makes the shear mode impossible.(2)The results of inoculation of bacterial blight at booting stage showed that the length of OsHIN1 over-expression and synonymous mutant over-expression was significantly longer than that of wild type,and the length of lesion was positively correlated with the expression level.It indicates that OsHIN1 is susceptible response gene and OsmiR1858a is a disease resistance factor.(3)Inoculation of bacterial blight P6 results demonstrated that OsHIN1 over-expressing transgenic rice had higher growth rate than wild type and higher bacterial content per unit leaf,whereas in the pre-OsmiR1858a over-expressing transgenic rice has opposite phenotype.(4)The results of agronomic traits of transgenic rice at maturity were showed that OsmiR1 858a had a significantly in plant height and 100 grains weight compared with wild type,while other transgenic rice had no difference.OsmiR1858a over-expression could improve rice resistance and conducive to the accumulation of organic matter.(5)OsmiR1858a gene promoter + GUS transgenic rice in GUS staining indicated that the OsmiR1858a gene was expressed in buds of germinated seeds and leaves.