Transcriptome Analysis Of Vernalization Of Brassica Rapa

Brassica rapa is a leafy vegetable that belongs to the Brassicaceae family.It originated in China and has been widely distributed throughout the country,accounting for a wide area of vegetable cultivation.B.rapa is a biennial plant of seed vernalization type and plant vernalization type.It is generally planted in the late summer and autumn.Spring planting was later developed to meet the demand for supply throughout the year.In the early spring environment,B.rapa will experience low temperature and long daylight,which cause B.rapa to prematurely bolt and flower,thereby causing the plant to lose some of its commercial value.However,quickened bolting is a rapid breeding method that can help produce better accessions faster.Therefore,detailed studies are needed on the effect of low temperature vernalization on the growth and development of B.rapa.In this study,two types of B.rapa with bolt-tolerance were selected for vernalization and long-day treatment at seedling stage,fixed long-day and vernalization temperature parameters,gradient vernalization time,and selected key periods for transcriptome sequencing.The self-organizing feature map(SOM)and weighted gene co-expression network analysis(WGCNA)were performed on the genes,and the key genes related to vernalization were selected to lay the foundation for the study of vernalization of B.rapa.The results are as follows:1.RNA-seq readed 974,584,922 data,a total of 291.28 Gb.Compared to the reference genome of B.rapa,44,799 known genes and 2,280 new genes were identified.2.SOM analysis of 21,035 differentially expressed genes was screened from the sequencing results of two B.rapa material transcriptomes.The analysis showed that transcripts related to plant hormone signal transduction pathway,starch and sucrose metabolism,photoperiod and circadian clock pathways,and vernalization pathways all changed significantly during different vernalization periods.In addition,the genes of TPS,UGP,CDF,VIN1 and seven hormone pathways in vernalization have different expression patterns,which can be used as candidate genes for vernalization in B.rapa.3.Low-abundance and low-variability filtering was performed on the transcriptome-sequenced genes,and 5748 and 5527 genes of two B.rapa were screened for WGCNA analysis,and two gene co-expression networks were constructed to reveal co-expression modules under different treatment.It was found that polysaccharide metabolism may promote shoot system morphogenesis during vernalization;carbohydrate metabolism,response to chitin,abscisic acid,and ethylene-activated signaling pathway may be important biological functions of B.rapa flowering transformation;BBX32,SUS1,PAO,TSF and NAC029 are hub genes and have biological functions of flower development.These genes have different expression patterns during vernalization of two B.rapa and can be used as candidate genes for vernalization.4.qRT-PCR detection of key genes obtained by SOM and WGCNA analysis,the expression trend was consistent with the measured transcriptome data,which proved the reliability and availability of the data.At the same time,the different expression of these genes under the vernalization of two B.rapa revealed different vernalization mechanisms.