Cloning And Functional Analysis Of CmERF053 And CmIPT1,Which Regulate The Axillary Bud Development In Chrysanthemum

Chrysanthemum has many different plant architecture,and it is very difficult to control its lateral branches chemically.Nowadays removing the side branches are being done manually.Due to the high cost of manual pruning,it is necessary for us to breed a new type of Chrysanthemum with ideal plant shape and we believe that it is the most efficient way to achieve high and efficient production of Chrysanthemum with relatively low cost.Here,we isolated an APETALA2/Ethylene-responsive factor(AP2/ERF)transcription factor from chrysanthemum {Chrysanthemum morifolium ’Jinba’),CmERF053,the expression of which was rapidly up-regulated by main stem decapitation.Phylogenetic analysis indicated that it belongs to the A-6 group of the DREB subfamily,and the subcellular localization assay confirmed that CmERF053 was a cell nucleus protein.Overexpression of CmERF053 in Arabidopsis exhibited positive effects of plant lateral organs,which had more shoot branching and lateral roots than did the wild type.We also found that the expression of CmERF053 in axillary buds was induced by exogenous cytokinins.These results suggested CmERF053 may be involved in cytokinins-related shoot branching pathway.In this study,an altered auxin distribution was observed during root elongation in the seedlings of the overexpression plants.Furthermore,overexpress CmERF053 gene could enhance drought tolerance.Together,these findings indicated that CmERF053 plays crucial roles in regulating shoot branching,lateral root and abiotic stress in plant.We cloned IPT1 homologous gene from chrysanthemum variety ’Jinba’.This gene has the structural domain of IPT gene family,so we named it CmIPT1.Evolutionary tree analysis showed that the origin of CMIPT1 is similar to the IPT family genes from other plant varieties.However,its genetic relationship with Cynara cardunculus is close while it is relatively distant with Lotus japonicas.Results showed that IPT1 is expressed in the roots,leaves,stems,shoot apex.And,its expression level is higher in the stem and apex compared with the roots and leaves.We found that the expression of IPT1 in different development phase of the auxiliary bud,from the dormancy stage to growing stage,showed significant increasing.The expression of CmiPT1 was higher in the Chrysanthemum’Jinba’ which has many lateral branches,while it was much lower in the Chrysanthemum ’Shenzhi’ which has less lateral branches.This result illustrated that cytokinin is the main factor which effects the shoot branching of Chrysanthemum.Decapitation experiment results showed that CmIPT1 could respond very quickly to the change of auxin.When overexpressing CmIPT1 inArabidopsis,the number of lateral branches increased significantly in the transgenic plants.This showed that CmIPT1is positivelyregulatethe development of lateral branches of plant.We also found that overexpression of CmIPT1 inhibited the transcription levelsof strigolactone synthetic genes CCD7,CCD8,and MAX1 in Arabidopsis.In this study,CmERF053 and CmIPT1 regulate the development of lateral branches of plants,which will provide theoretical basis and candidate genes for plant molecular breeding for architecture.