Identification Of MiRNA Families Associated With Phase Transition And Preliminary Study On The Functions Of Key MiRNA In Chinese Jujube

Phase change plays a crucial constructive role in plant life,which has indispensable impacts on fruit breeding process and early-harvesting cultivation.Compared with other fruit trees,Chinese jujube(Ziziphus jujuba Mill.)has unique characteristics of extremely short juvenile phase and fast flower bud differentiation.Current studies have interpreted that a number of microRNA(miRNA)families are involved in flowering time control and phase transformation of high plants.Therefore,it is pretty suggestive for the phase transition regulation of fruit trees to probe into microRNA family associated with phase transformation in jujube trees.In this study,the new shoots at different development stages(nodes)of jujube progenies were used as materials.We identified miRNA related to phase transition by Small RNA sequencing and predicted their target genes by TargetFinder.Furthermore,to screen out the critical regulatory roles of the key miRNA and genes during jujube phase transformation,the expression patterns and relationships between miRNA and their target genes were analyzed.Afterward,three key miRNA were overexpressed in Arabidopsis thaliana.The main results obtained are as follows:(1)28 miRNA families with 58 known miRNA and 23 novel miRNA were identified by Small RNA sequencing analysis in the three different development stages of juvenile,transition and adult period.Among them,44 miRNA were differentially expressed,including 32 known miRNA and 12 novel miRNA.(2)6 miRNA(zjmiR156a-5p,zjmiR156j,zjmiR172c,zjmiR172e-3p,zjmiRnovel-16 and zjmiRnovel-71)with obviously differential expression in the three development stages were screened out.Their 15 key target genes were also predicted through TargetFinder software,and they are mainly involved in transcriptional regulation and biosynthesis.(3)The differential expression of the above-mentioned 12 miRNA and their 15 key target genes during phase change were verified by qRT-PCR,and they had positive or negative regulatory relationships.Moreover,the two newly discovered miRNA(zjmiRnovel-16 and zjmiRnovel-71)may affect the phase transition through photoperiod pathway and glucose metabolism pathway,respectively.(4)Compared with the wild type,phenotypic analysis of overexpressed by zjmiRnovel-71 in Arabidopsis thaliana exhibited some changes.The transgenic lines have the traits of short-life-cycle,smaller single leaf area,increasing number of flowers.Overexpression of zjmiRnovel-71 led to a delay in flowering time and prolong in flowering period.