Comparative Study On Photosynthetic Characteristics And Petal Transcriptome Of Tree Peony ’Luoyang Hong’ On Two Rootstocks

At present,the incompatibility of container cultivation of grafted tree peony(Paeonia suffruticosa)limits its application.In order to explore the mechanism of specific rootstocks to improve growth and flowering of potted grafted tree peony,in this study,roots of Paeonia broteri(PGPB)and Paeonia ostii(PGPO)were grafted with Paeonia suffruticosa ‘Luoyang Hong’ as the experimental material to analyze the differences in photosynthetic characteristics,in sugar content of various tissues and in transcriptional regulation of petals between PGPB and PGPO.By analyzing these differences,it lays the foundation for clarifying the working mechanism of excellent rootstocks and screening and cultivating tree peony varieties that are more suitable for potted breeding.The main results are as follows:The photosynthetic characteristics and chlorophyll fluorescence parameters of PGPB and PGPO were measured by LI-6400 and MINI-PAM.In the vigorous growth stage of tree peony leaves,from the full flowering stage to the summer dormancy stage,the Pn of PGPB was higher than that PGPO.From the round peach stage to the full flowering stage,the Pn,CE,WUE,Fm,Fv/Fm,Y(II)PGPB were increased by 145.86%、245.10%、60.68%、33.27%、8.45% and 25.00%,all were larger than PGPO.In the post-anthesis growth stage,q N PGPB was significantly higher than PGPO.The leaves of PGPB had higher light utilization efficiency and Paeonia broteri roots are more suitable as rootstock for potted ’Luoyang Hong’.During the full flowering stage,the sucrose content of PGPB petals(44.76 mg·g-1)was significantly higher than PGPO(30.40 mg·g-1)47.24%,and the starch content(44.30 mg·g-1)was significantly higher than PGPO(31.19 mg·g-1)42.03%,reflecting the large reservoir strength of PGPB petals to achieve the unloading and storage of sucrose.The transcriptome of PGPB and PGPO petals in the full flowering stage was sequenced to obtain clean data of 41.84 Gb.80,390 Unigenes were obtained by sequence assembly.The Unigene sequence was compared with 8 public databases to obtain 30,421 Unigenes with annotation information,accounting for 37.84% of all unigenge numbers.Gene differential expression analysis showed 439 DEGs.With PGPO as control,98 genes in PGPB petals were up-regulated and 341 genes were down-regulated.The functional classification and enrichment of DEGs indicated that the gene expression differences of the two grafted ’Luoyang Hong’ were mainly reflected in the starch and sucrose metabolic pathways,the cell wall polysaccharide modification pathway and the signal transduction pathways involving hormones,ROS and protein kinases.The sucrose transport-related protein genes CWINV1(c68877.graph_c0),INV1(c81829.graph_c0),SWEET5(c51487.graph_c0),and STP14(c68255.graph_c0)associated with flowering regulation were down-regulated in PGPB petals,whereas ANN(c71608.graph_c0))was up-regulated expression in PGPB petals.An Annexin gene was cloned from the petal of ’Luoyang Hong’ by the method of TA cloning,named Ps ANN1,and the Gene Bank accession number was MK550694.The full-length c DNA of this gene is 939 bp,encoding 312 amino acids with a relative molecular mass of 35542.6 and an isoelectric point of 8.20.The amino acid sequence encoded by this gene has the highest similarity with the Corchorus capsularis Annexin gene OMP03638.1,reaching 78.14%.The protein has four functional domains and belongs to the Annexin family of proteins.The relative expression of Ps ANN1 in the petals of two kinds of grafted ’Luoyang Hong’ wind bell stage,round peach stage,full flowering stage and flowers falling stage was obtained by q RTPCR.The real-time fluorescence quantitative results showed that the Ps ANN1 expression of PGPB petals was 5.14 times higher than that of PGPO during full flowering stage,and the expression of Ps ANN1 in PGPB petals was 489.31 times higher than that of wind bell stage during this period,indicating that the expression of Ps ANN1 played an important role in the flowering transformation from wind bell stage to the full flowering stage and the flowering process to regulate the flowering difference of two kinds of grafted ’Luoyang Hong’.In summary,roots of Paeonia broteri is more suitable as the rootstock of the potted ’Luoyang Hong’,and the Ps ANN1 gene plays an important role in regulating the flowering difference of the two grafted ’Luoyang Hong’.