Analysis Of MiRNAs And Its Targets In Response To Hg Stress In Medicago Truncatula

MicroRNAs(miRNAs)are a class of small RNAs composed of 20-24 nucleotides.They can regulate gene expression at transcriptional and post-transcriptional levels.Since the industrial revolution,mercury pollution is becoming more serious.Mercury has harmful effects on plants.Researchers found a large number of plant genes in response to heavy metal stress by transcriptome analysis.As an important regulatory factor,the role of miRNA under heavy metals stress,such as cadmium and mercury,is of particular interest.Thus,identification of miRNA and its targets is important to understand the regulatory mechanisms.In this study,we collected Meidicago truncatula sRNA sequencing and degradome datasets for identifying novel miRNAs and their target genes using bioinformatic methods based on the updated M.truncatula genome.Agilent microarray was used to observe M.truncatula miRNA and its target gene expression under Hg stress.The main findings are as follows:(1)This study identified 24 new miRNAs,Using five degradome datasets,323 type I target genes were identified including 147 for newly discovered miRNAs based on the 46 Medicago truncatula sRNA sequencing libraries.There are 91 transposable element targets identified by similar method.(2)The microarray data shows that among the 323 target genes,140 genes including 118 in root and leaves 49 could be differentially regulated by Hg stress.These differentially expressed genes involve transcription factors,disease resistance protein and transmembrane protein.(3)To understand the pathways that may play an important role under Hg stress,we made GO enrichment analysis of differentially expressed target genes,and a hierarchical clustering for 140 differentially expressed genes.Our data show that 27 GO terms were significantly enriched.These GO items are mainly related to gene expression,metabolic regulation,secondary metabolism and biosynthesis progresses.