The Role Of Poly Comb Group In Regulation Of Leaf Margin Development In Arabidopsis

Leaf is the most important photosynthesis organ in plant.In agriculture,the economic values of most vegetables are from the leaf.Therefore,the research on leaf development is from vital practical significance.In the common leaf margin model,auxin,PIN1,CUC2 and MIR164A are key regulators in leaf serration development.Here,this thesis focuses on the role of polycomb group(PcG)proteins in regulation of leaf margin development in Arabidopsis.We aim to create a new leaf serration model and to discover the new mechanism of leaf margin development.This paper introduce the epigenetic mechanism into the study of leaf margin development for the first time,providing theoretical guidance for the new varieties and improvement of leafy crop plants in modern agriculture.1.Leaf serration analysis of PcG mutants in ArabidopsisLeaf serration was analyzed in PcG mutant emf2-10 vrn2-1(ev)plants.ev has high level of leaf serration,which is disappeared when we removed CUC2.That indicate CUC2 is necessary for serration in ev mutants.Furthermore,the teeth number was not significant changed between ev and La-0.The tooth tip,tooth sinus and leaf outline were analyzed between cuc2-1D and ev.Results revealed that the tips of cuc2-1D were growing faster than wildtype,and sinuses of cuc2-1D were growing slower than wildtype.However,this model was not identical with ev.The leaf serration of ev was more depended on the inhibit of growth in the sinuses.2.CUC2 function and interaction in leaf margin developmentThe tooth tip width and sinus width of cuc2-1D were analyzed in this thesis.The results showed that the tooth tip width of cuc2-1D is longer than Col-0.Therefore,the tooth sinus width of cuc2-1D was shorter than Col-0.That signified CUC2 promote leaf tip growth and repress leaf sinus growth.Real-time PCR showed that CUC2 can repress the expression of STM,KNAT1,KNAT2,KNAT6,EPFL2 and DPA4,which are very important leaf margin factors.That extended the signaling pathway of leaf margin development.3.Genes expression,location in PcG mutant and new leaf margin model creationExpression of CUC2?CUC3?STM?KNAT1?KNAT2?KNAT6,EPFL2 and DPA4 in ev were higher than La-0.However,the expression of MIR164A,MIR164B,MIR164C in ev were lower than La-0.That illustrated PcG could control leaf margin development through many leaf margin genes.In the leaf tips,auxin level of ev was lower than La-0.However,the CUC2 level of ev was higher than La-0 in the leaf sinus.That indicted the leaf serration of ev is result of the balance between auxin and CUC2 in Arabidopsis.The ChIP results revealed that PcG protein CLF bind the CUC2 DNA locus,which indicted that CUC2 was PcG target gene.MIR164A was detected in the leaf tips and vein of La-0,but cannot detected in ev leaf vein.Real-time PCR showed MIR164A level in ev is lower than La-0.That indicted PcG might control CUC2 expression through MIR164A.Finally,this thesis researched on the biological function of PcG in regulation of leaf margin development and creates a new leaf serration model.