Analysis Of Transcriptome Characteristics During Flower Bud Initiation And Development Of Chimonanthus Praecox L.

Wintersweet(Chimonanthus praecox(L.)Link),belonging to Calycanthaceae,Chimonanthus,is traditional precious ornamental woody plant and has been cultivated in China for about 1000 years.Wintersweet has highly ornament and commercial value because it flowers in cold winter which different with common woody plants that flower in spring or summer,as we as it’s yellow petal and special fragrance.There is no report about why it flowers in such cold season and only few research focused on the observation of paraffin section of different stage in the development process of flower bud with no molecular research.In this study,we sampled the flower bud of wintersweet and take a transcriptome sequence combined morphological study of flower bud in different development stage.And we get full transcription data in the process from flower initiation to flowering,Combining with morphology change,we analysed the different expression genes(DEGs)in important stage between flower development and the result is :1.We get 10 transcription data base of typical development stage: UD,TLF,TPD,SPD,PPD,FBD,sFBD,OOF,AF,EFP respectively after a succession sampling process while flower bud development,followed by RNA extraction and transcriptome sequence.Combining with correlation relationship and Principal component analysis of sequence data as well as observation result of flower bud development process,We divided the 10 stage into 3 key development periods: flower bud differentiation period(UD-SPD);flower organ development period(FBD-AF);early flower period.We identified 15426 different expression genes in all stage of flower bud initiation and development.2.In flower bud initiation period,we identified 27 key candidate genes which may participate in regulating flower initiation and expression pattern analysis in flower and leave of these genes showed that 3 pathway :GA pathway,photoperiod pathway,sugar metabolic pathway may regulated flower initiation in wintersweet.Analysis of different expression genes found that MADS gene family may have important role in flower initiation.After sequence alignment of flower meristem specific gene AP1 between wintersweet and other species,we found that AP1 in wintersweet is more likely to FUL in Arabidopsis,which can explain there is no differentiation of petal and sepal.3.Focusing on the phenotype of slow growth(sFBD)in the flower organ development process,we found lots of heat shock protein were up regulated,on thecontrast,lots of genes related to cell proliferation and division were down regulated,infering that outer high temperature may result this phenomenon.Expression pattern analysis of identified genes related to growth regulation found that 25 genes including sugar metabolic,transcript factor and temperature response factor may play a regulatory role in this stage.165 genes related to plant hormone were basically down regulated in this stage,consistent with the phenotype of slow growth.Co-expression analysis of all DEGs and identified 13 genes related to the regulation of flower organ found that 13 potential genes may participated in the regulation of those flower organ regulated genes,and some of them can inhibit flower organ development.4.Analysis for transcriptome data in the stage before and after bloom found that genes related to anther and ovule development were still up regulated till bloom,which imply that when the pollen grains got formation in October 24,the pollen and ovule were developing all the time till the flower going to bloom in December 25.This could also explain why the wintersweet did not bloom when all the flower organ appeared.Considering that there may have a dormancy process before bloom,we analysed the expression pattern of genes identified which potential regulate dormancy process,like SVP,SVL,DAM,CO/FT,before and after flowering,and among of these genes,only SVP-like and TCP18-like expression pattern can meet the dormancy process,therefore,whether there is a dormancy process before flowering of wintersweet remains to be further studied.5.Wintersweet bloom precisely in winter after a development process contains 10 typical stage in 3 important periods.This article summered the difference of genes expression in all the development stage and a large number of candidate genes involved in those development proccess were found.And basically revealed that how the expression changes of genes behind the process between flower initiation and flowering.Based on these data,we can regulate the flower time of wintersweet by changing some important development process in our subsequent study.