The Regulating Mechnism Of Milrna LET-7at Three Life Stages Of Potato Pathogenic Oomycete,Phytophthora Infestans

Potato late blight is one of the most destructive diseases. The oomycete pathogen, Phytophthora infestans infects potato stem, leaf and tuber. This disease can potentially wipe out the entire crop, causing the massive loss in the main production areas of potato all over the world. MicroRNA (miRNA) is a class of21-22bp, single stranded RNA molecule, which are involved in regulating cell cycle and development by base-pairing of target mRNA to restrict the gene expression in plants and animals. The genome of P. infestans strain T30-4has been sequenced, the RNAi pathway also has been described. But the regulating mechanism of micro-like RNA (milRNA) in P. infestans have not been reported. Based on three constructed smll RNA databases at the three life stages (sporangia, germinating sporangia and mycelia) of the P. infestans strain YN-YJ54.1, and more than1000conserved milRNAs and their target genes. The milRNAs let-7, miR1491, miR1498and miR4066-3p were detected by small RNA qPCR and northern blot to verify their relative transcript levels. qPCR and5’RACE demonstrated that the gene PIK-A was regulated by let-7through mRNA cleavage by binding with imperfect complementarity to a site within encoding region at the mycelia and germinated sporangia stages.Sporangia can germinate directly or release zoospores by using the tube like hyphae to invades the plant leaf or root. Therefore, we predict that the target gene may be related to this stage of infection. Our analysis shed light on the alternative molecular tools for control P. infestans in potato.