Bioinformatics Analysis Of MADS-box Gene Family And Expression Analysis Of Genes Involving To Floral Organs Development In Tree Peony

Tree Peony(Paeonia suffruticosa)is a perennial woody plant of paeoniaceae,which has high ornamental value.flower organs and structure of tree peony have changed greatly during long-term evolution,which is of great significance to enhance its ornamental quality.The MADS-box transcription factor plays an important role in the development of floral organs,but its molecular regulation mechanism is still unclear.Based on the peony transcriptome database,19 MADS-box transcription factors were identified and systematically analyzed by Bioinformatics.3MADS-box genes related to the development of floral organs were selected and cloned from 19 MADS-box transcription factors.Meanwhile,The expression characteristics of 3 mads-box genes were analyzed in different tissues of peony,at different stages of flower bud differentiation and at different flower types of peony by combining paraffin sections and real-time quantitative PCR.Here are main results:19 MADS-box genes(Ps MADS)with full ORF were identified from the peony transcriptome database and named MADS1-19.Physical and chemical analysis showed that the predicted 19 MADS-box gene family members encode protein ranged from158-365 amino acid residues(aa)in length,and protein molecular weight varied from17933-41328 Da,isoelectric point(p I)in the range of 5.41-9.92.19 MADS-box genes had highly conservative MADS-box domain,MADS1-16 had sub-conservative K-box domain.subcellular localization analysis showed that most of the Ps MADS protein were located in nucleus.Ps MADS13 was located in cytoplasm.Phylogenetic analysis revealed that 19 Ps MADS genes could be divided in ten groups,16 MADS-genes belong to MIKCcand others belong to Type I.Ps MADS5?Ps MADS7?Ps MADS12 gene with full CDS were isolated from the flower petals of tree peony‘Luo Yang Hong'.A full CDS length of Ps MADS5?Ps MADS7?Ps MADS12 gene was 729bp?732bp?636bp,encoding 243?244?212amino acid respectively.The accession number in Gen Bank:MH169596?MH563611?MH169595,respectively.Sequence comparative analysis showed that Ps MADS5?Ps MADS7?Ps MADS12 were more than 77% consistent with SEP1?AGL6 ?PI homologous protein of other plants.The phylogenetic tree showed that tree peony was close relationship with Rose plant.The expression levels of Ps MADS5?Ps MADS7?Ps MADS12 genes were significantly different in different organs(root,stem,leave,fruit and flower bract).The expression level of Ps MADS5 was higher in the bud and stem,which was 5.07 and 3.92 times of the expression level of fruit,followed by the expression level of fruit,and the expression level of leaves and roots were lower.Theexpression level of Ps MADS7 was the highest in the bud,which was 8.16 times of the expression level of fruit.The expression of Ps MADS12 was highest in the bud and lower in other organs.The flower bud differentiation of‘Luo Yang Hong'tree peony can be divided in six stages : the initial stage of differentiation,the bract primordia differentiation stage,the sepal primordia differentiation stage,the petal primordia differentiation stage,the stamen primordia differentiation stage,the pistil primordia differentiation stage.Flower bud differentiation began in the early June and ended in the middle November.The expression level of MADS-box genes showed significant differences during the development of flower buds.Ps MADS5 and Ps MADS12 were all expressed during the flower bud differentiation period,and the expression level was relatively low in the first four periods,which the expression level was significantly increased in the stamen differentiation stage,and the pistil differentiation stage was the highest,which was 43.25 times and 101.1 times of the expression level in the initial differentiation stage.The expression level of Ps MADS7 was‘high-low-high'during the differentiation process of flower buds.The expression level was higher at the initiation stage of flower buds?stamen and pistil,and the expression level was the lowest at the differentiation stage of sepal.The expression levels of three MADS-box genes were significantly different in the organs of two flower types of tree peony(‘Qian ceng'and‘Lou zi').And the expression levels of different flower types of tree peony presented certain regularity.the expression level of Ps MADS5 was highest in the sepal,the expression level of Ps MADS7 was higher in the sepal and pistil.The expression of Ps MADS5 and Ps MADS7 were the lowest in the stamen of flower type(‘Qian ceng').the expression level of Ps MADS5 and Ps MADS7 in the inner petal of flower type(‘Lou zi')were significantly higher;The expression level of Ps MADS12 was the highest in the petal of flower type(‘Qian ceng').The expression level of Ps MADS12 was the highest in the inner petal of flower type(‘Lou zi').The expression of Ps MADS12 was the lowest in the pistil.In conclusion,There are at least 19 MADS-box gene members in tree peony,and the protein structure and physicochemical properties encoded by them from the same subfamily are similarity.Ps MADS5 may have the functions of regulating stamen primordia differentiation,pistil primordia differentiation,and the development of sepal;Ps MADS7 may have the functions of regulating meristem differentiation,stamen primordia differentiation,Pistil primordia differentiation,the development of sepal and pistil;Ps MADS12 may mainly involve in stamen primordia differentiation,pistil primordia differentiation,the development of petal.As the innter petal derived from stamen petaloid in‘Lou zi'flower type,it is speculated that Ps MADS5,Ps MADS7,Ps MADS12 may participate in the stamen petaloid in‘Lou zi'flower type.