The Molecular Mechanism Of MicroRNA-regulated Polarity Of Leaves

microRNAs (miRNAs) are 21-24 nucleotide single-stranded RNA molecules , and double strand RNA binding protein HYL1 is necessary for microRNA biogenesis. HYL1 can process the primary microRNA into mature microRNA, Together with DCL1 and AGO1, HYL1 directs the processing of target gene to regulate the expression at post-transcript level. Our research involved in microRNA mainly is focused on the development of plant. Homeodomain-leucine zipperâ…¢(HD-Zipâ…¢) gene family is involved in leaf polarity, and determination of leaf adaxial identity. HD-Zipâ…¢are the targets of miR165/166, which regulate the gene expression at post-transcriptional level and recapitulate the establishment and maintenance of leaf polarity further.The leaves of hyl1 are hyponastic and curved upward, but in the leaves of hyl1 double mutants with (hyl1 rev-6, hyl1 rev-9 and hyl1 phb-6 phv-5), the curved leaves were recovered to wild phenotype; conversely, the hyl1 phenotype of curvature was aggravated in hyl1 ren-10D double mutant. That is to say the phenotype of hyl1 was responsible for the overexpression of REV, PHB and PHV. Because HYL1 mediated the maturation of microRNA , in hyl1 mutant the efficiency and quantity of micro RNA processing reduced, leading to decreased amount of mature microRNA and the increased expression of REV, PHB and PHV increased. RT-PCR and REAL-TIME PCR experiments demonstrate the expression levels of REV, CNA , PHB and PHV are higher in hyl1 than in wild-type plant. The result of paraffin sections indicate REV, PHB and PHV not only determine leaf polarity but regulate the arrangement of xylem and phloem.To further investigate the interaction between HYL1 and AGO1, the AGO1 was clone and construct to pMAL expression vector, and the expression experiment was performed , which is also convenient for research of interaction between AGO1 and leaf polarity.