Mapping And Analysis Of Flower Type And Flower Size Traits In Peach (Prunus Persica)

Peach(Prunus persica)originated in the west of China belongs to Prunus of Rosaceae.The fruit flavor is excellent,and flower is of great ornamental value.The flower type of peach could be classified into two types,including nonshowy and showy.The corolla of nonshowy flower is smaller,and that of showy is larger.Flower size is another important trait of floral organs,which could be divided into five grades according to the size of floral diameter.The genes controlling flower type and flower diameter in peach were not clear yet.It has been an important topic of exploring flower organ size traits.In this study,a Fi population from the cross ’Huangshuimi’ × ’Zhongyoutao14’was used to create two genomic DNA pools ’showy’ and ’nonshowy’.Meanwhile,five different periods of flower development were selected for comparative RNA-seq analysis.Combining the variations and expression patterns of genes at the mapping region,two candidate genes were selected and transformed into Arabidopsis thaliana to verify function.PpAIL6 was further confirmed as the candidate gene of flower size based on the differentially expression between small and large flower,and also transformed into Arabidopsis thaliana to verify function.On the one hand,these results provide theoretical support for candidate gene screening and functional verification of peach flower type and flower size traits.In addition,due to the small genome of peach as a model plant in fruit trees,the study of its floral organs can provide ideas for the study of floral organs of ornamental plants.The main research results are as follows:1.Sequencing of the two genomic DNA pools ’showy’(25 progeny)and’nonshowy’(25 progeny)to a 48.38×(showy)and a 54.96×(nonshowy)genome coverage allowed detection of DNA variants.Conducting variant allele frequency and density-based mappings revealed a genomic region with a significant association with flower type,14.4-16.36 Mb on chromosome 8.PpB3-1(PRUPE.8G122500)and PpB3-3(PRUPE.8G122700)were selected as candidate genes according to the gene annotation and variants of DNA between two flower types.2.The total transcriptome of petals of two flower types from five different periods(buds period;red dot period;1:lperiod(Area ratio of petal/sepal);budding flower period;and full bloom period)were analyzed using RNA-seq.The expression patterns of all genes could be classified into 12 clusters.In cluster 5,the expression levels of genes showed significantly higher in showy than that in nonshowy at the flower bud period.Functional analysis showed that the genes in cluster 5 were significantly enriched in pathway plant hormone signal transduction.In combination with the previous mapping results,the expression levels of candidate genes PpB3-1 and PpB3-3 also showed significantly different between two flower types at the flower bud period confirmed by qRT-PCR.3.Overexpression vectors of PpB3-1 and PpB3-3 genes were constructed for genetic transformation of Arabidopsis thaliana to verify function.The results showed that there was no significant difference in floral organ size between the overexpressing PpB3-1 lines and the wild-type plants.While,the overexpressing PpB3-3 lines showed significantly reduced petal length and surface area.Above results indicated that PpB3-3 might be involved in regulating flower organ size.4.The expression level of the candidate gene PpAIL6 was significantly different between the two cultivars at the bud stage by analyzing the gene expression level in the flower diameter region(chr06:20.38 Mb-21.66 Mb).PpAIL6 gene overexpression vector was constructed to identify the function of genetic transformation in Arabidopsis thaliana.The results showed that the overexpressing PpAIL6 line showed larger petal length,width,surface area and flower size compared with that of the wild type plants.These results indicated that PpAIL6 plays an important role in regulating floral organ size.Subcellular localization showed that PpAIL6 protein was expressed in the nucleus.