Identification And Functional Analysis Of Pathogenic MicroRNAs In Phytophthora Infestans

Being one kind of approximately22nt long small RNAs, microRNAs (miRNAs) have shown their pivotal roles in both growth development and stress responses. In recent years, more and more researches have shown that miRNAs participate in regulating the process of pathogen and plant interactions. Phytophthora infestans (P. infestans) is a major pathogen that causes devastating late blight of potato and tomato. However, there have been few systematic researches on miRNAs in P. infestans, let alone researches on pathogenic miRNAs. Based on the above, by using bioinformatic strategies, we comprehensively predicted and identified pathogenic miRNAs that may exist in P. infestans. Then, we analysed the function of pathogenic miRNA in P. infestans, via molecular biology experiment.First, a total of128putative miRNAs belonging to66miRNA families were identified by bioinformatic approaches.33vital pathogenic miRNAs were screened by constructing miRNA-miRNA relationship network. Two potential pathogenic miRNAs located in the central and two in the edge were chosen for detection. Two miRNAs (pi-miR466and pi-miR1918) were successfully detected, which demonstrated their exsistence in P. infestans.Then, the expression quantity of pi-miR466and pi-miR1918was further analysised by performing qRT-PCR under different time of treatment. Both miRNAs changed dramatically at the second day after incubating tomato leaves, implying that they are potential pathogenic miRNAs.Finally, we chose ath-pre-miR159a as the frame sequence, and successfully constructed amiR466expression vector. After being transiently over expressed in tomato leaves, miR466inhibited the occurrence of late blight and improved the resistance of tomato.The study reported here not only first predicted an identified of pathogenic miRNAs in P. infestans, but also provided basis for the molecular mechanism in pathogen and plant interaction.