Characteristic And Functional Analysis Of MiR1918 In Tomato And Phytophthora Infestans Interaction

microRNAs (miRNAs) are one kind of 21-24 nt single-stranded non-coding small RNAs, which widely exist in organisms. By silencing target genes, miRNAs regulate biological processes such as development, metabolic pathway, stress reponse and so on. Recently, miRNAs have also been proved to be pivotal molecules in plant-pathogen interaction, highly associated with host resistance and pathogen pathogenicity. Tomato is major crop plant that is widely cultured around the world. Annually, tomato late blight that is caused by the infection of Phytophthora infestans (P. infestans) leads to a tremendous loss in tomato production. However, miRNAs involved in tomato and P. infestans interaction have not been further studied. Meanwhile, miR1918 that both exists in tomato and P. infestans has not arroused much attention. Based on aforementioned background, the research here performed the characteristic and functional analysis of miR1918 in tomato and P. infestans interaction mainly via plant genetic engineering.Firstly, target genes of miR1918 in tomato (sly-TG1, sly-TG2 and sly-TG3) and in P. infestans (pi-TG1, pi-TG2 and pi-TG3) were predicted via bioinformatic methods, which may be highly associated with host resistance and pathogen pathogenicity. By using real-time quantitative PCR (qRT-PCR), miR1918 was detected to have different expression profiles in tomato and P. infestans respectively during their interaction, further leading to the expressional changes of its target genes. The result assumed that miR1918 may have vital roles in tomato and P. infestans interaction.Then, based on the precursor backbone of Arabidopsis miR159a, artificial miR1918 (amiR1918) is engineered by replacing mature miR159a/mi159a sequence with miR1918/miR1918* sequence respectively via the strategy of PCR introducing mutations. amiRl 918 plant expression vector were further constructed.Finally, transgenic tomato transiently and stablely over-expressing amiR1918 both developed attenuate resistance against P. infestans, in which the target genes were suppressed. The result demonstrated that miR1918 participates in tomato and P. infestans interaction through the depression of its target genes.