The Promoter, Targets And Preliminary Function Analysis Of A Novel MicroRNA-HAT4in Arabidopsis Thaliana

Phytophthora is a geuns of oomycetes,which are morpholgically similar to fungi, andthey represent many destructive pathogens. Phytophthora are able to infect many crops andflowers, trees, causing catastrophic damages and serious economic losses to agricultureevery year. MicroRNAs (miRNAs) play important role as regulatory factors to eukaryotes andprokaryotes. In terms of plant disease resistance, disease-related miRNA activate or inhibitthe expression of resistance genes by directing mRNA cleavage to activate or inhibit plantdefense system.HAT4is a novel miRNA we found in Arabidopsis and was specificlly inducedby Phytophthora,but not induced by fungi, bacterial,or abiotic stress.Thus, HAT4may play animportant role in the process of Phytophthora-Arabidopsis interaction.In this reseach, we employed the model Arabidopsis-Phytophthora interactionpathosystem and Nicotiana-Phytophthora interaction pathosystem to understand regulatorymechanisms of HAT4promoters, targets and function. In the following, we would showed theresults we found.1.The stable expression analysis in Arabidopsis and transient expression in Nicotianashowed the core of HAT4promoter, which is positive regulatory region, was upstream within200bp; the upstream of the200bp-1200bp is the negative regulatory regions, yetwe foundNicotiana was lack of actingfactors at these regions.2.The semi-quantitative and quantitative analysis showed that the T1/T2were HAT4target genes from six candidates target. T1/T2encoded a transcription factor NAC that weredown-regulated expression when Phytophthora was infecting Arabidopsis. This expressionpattern was associated with HAT4.3.Overexpressing HAT4changed the phenotype in Arabidopsis. Specifically theoverexpressing transgenic plants generally short, leaf malformations, and growth slowly.Phytophthora-inoculated in transgenic plants showed that overexpression of HAT4were ableto increase disease resistance in plant.In conculsion, the analysisof HAT4promoter, targets and function provides important insights into understanding the role of microRNAs in the plant-oomycete interaction.