Transcriptome Analysis Of Flowering Induction,Trees At Different Phases And Cloning Of Genes Related To Flowering In Platanus Acerifolia

London plane(Platanus acerifolia)is a widely used street tree and important city landscape tree as "king of street trees" by virtue of its characteristics of rapid growth,excellent shading capacity from broad crowns and good tolerance to pruning and strong adversity resistance.However,various characteristics of the reproductive phase detract from the value of this tree,notably,the aerial dispersion of pollen and hairs from the achenes which can cause respiratory allergic reactions and itchy skin in the human population and pollute the urban environment.The aim of this study is to search important genes related to floral induction and phase change via analysing of gene expression profiles of Platanus sub-petiolar bud during floral induction and at different phases.Together with functional analysis of key genes related to floral induction and phase change,improving our knowledge of the molecular mechanisms underlying floral induction and phase change in London Plane.Such work would make contribution to sovle the problem of pollution of pollen and hairs from the achenes by breeding new cultivar via artificial modification of flower devopment and phase change.The major results as following:1.We generated a reference transcriptome of sub-petiolar buds and leaves from different pahse by RNA-seq.A total of 60,505 unigenes were obtained which were also annotated in Nr,Nt,Swiss-Prot,GO,KEGG and COG database.Further more,digital gene expression profiles of sub-petiolar buds from 3 stages during floral indcution were performed and identified differential expressed genes(DEGs).We studied the expression patterns and possible functions of flower-related and MADS-box gene.Relation about hormone-related genes with floral induction was also studied.We identified genes which were possible related to floral induction via analysis gene expression patterns and differential expressed genes.Transcription factors were further studied among possible floral incution related genes.2.Digital gene expression profiles of sub-petiolar bud in trees between the adult vegetative phase and the reproductive phase were peformed.245 up regulated genes and 123 down regulated genes in reproductive tree were identified by analyzing shared DEGs between multiple genetypes.Four flower-related genes possiblely controlling phase change were identified by analyzing expression levels of flower-related genes between trees in two different phases.23 up regulated and 10 down regulated transcripional factors were identified in DEGs.Functions of these transcription factors were further studied.3.We have isolated four SPL3/4/5 orthologous genes which possibly controlling phase change(PaSPL3a/b/c/d)from London plane tree.We investigated the role of these Platanus genes in flowering and phase change.Real-time PCR analysis demonstrated diverse expression patterns for the four PaSPL3 genes throughout the various P.acerifolia tissues,but all four were highly expressed in developing flower bud tissues.Expression of PaSPL3a/b/c in leaves changed according to the season and was regulated by temperature.Furthermore,three of the orthologous were found to induce an early flowering phenotype when overexpressed in Arabidopsis.The findings of this study indicate that PaSPL3 genes may participate in early stage inflorescence development in London Plane.However,there appears to be some divergence in the function of these genes in the control of phase change in London plane as compared to that within Arabidopsis.4.Two CO orthologous genes of London plane tree(PaCOL1/2)were isolated.Expression analysis showed that PaCOLl/2 were highly expressed in bud and root throughout various tissues.Both PaCOLl and PaCOL2 have circadian expression features during a day,but expression patterns were different.Based on expression patterns,PaCOL1 was possible up stream genes of London plane homologs of FT,SOC1 and FUL.Expresison of PaCOL2 changed according to season and peaked in Octorber,however,expression of PaCOLl was stable.Further study indicated PaCOL2 was regulated by temperature.Besides,PaCOLl expressed higher in bud of trees in adult vegetative pahse compare to reproductive pahse.Furthermore,both the two orthologous genes were unable to induce an early flowering phenotype when overexpressed in Arabidopsis.These results suggest that PaCOLl/2 have a likey function in flower development in bud.