Cloning And Expression Analysis Of Key Gene PsFT Of Long-day Photoperiod Pathway And Its Upstream And Downstream Genes PsCO, PsSOCl In Tree Peony (Paeonia Suffruticosa Andr.)

Tree peony （Paeonia suffruticosa Andr.） is belonged to one of China’s top ten flowers, referred toas ‘the king of flowers’ due to their rich palette of horticultural varieties and deep ethnobotanical historyin Chinese culture. Now it is cultivated extensively as a garden crop for its beautiful flowers, pleasantfragrance, and splendid color. Tree peony is flowering in late of April and the beginning of May, in thespring. The blossom time （about10-15day） is short and relative concentrated, compared with otherflowers. These characteristic limits the industrialization development of tree peony. During the pastyears, lots of forcing culture methods of tree peony was established. However, few papers were studiesthe molecular mechanism of flowering. In this work, the flower buds of tree peony cultivar ’LuoyangHong’ were used as materials to separate flowering genes by RT-PCR. Finally, one key gene PsFT oflong-day photoperiod pathway and its upstream and downstream genes PsCO, PsSOC1weresuccessfully cloned. This results could be studied the molecular mechanism of long-day photoperiodpathway. The expression profiles of three genes in different developmental stages of tree peony wereinvestigated by qRT-PCR. The results are as follows:（1） The coding sequence （CDS） of PsCO is1125bp, encoding373amino acids （GenBank accessionnumber is KF113358）. Bioinformatics analysis of PsCO showed that the majority of PsCO’s region ishydrophilic region, belonging to hydrophilic protein. Prediction of secondary structure suggested thatPsCO included more irregular curl. Compared with other homologous CO amino acid sequences, it wasfound that the similarity of PsCO from castor （XM₀02515336.1）, the mango （HQ585995.1） was69.2%and66.8%, respecitvely. The expression profile of PsCO showed that it was expressed higher inthe beginning of flowering buds differentiation, then decreasing and a littile increasing at last stage.（2） The CDS of PsFT was522bp, encoding174amino acids （GenBank accession number is KF113360）.PsFT belongs to hydrophilic protein. Prediction of secondary structure of PsFT suggested that it wasmainly consisted of curling, folding and a few α helixes. Analysis of structure domain prediction ofPsFT showed that it contains a PEBP structure, which belongs to the PEBP family members. Theexpression of PsFT was gradually up-regulated from flowering buds differentiation to flowering budsformed and then decreased at last stage. The expression of PsFT may regulate the expression of PsCO.（3） The CDS of PsSOC1is678bp, encoding226amino acids （GenBank accession number isKC493630）. PsSOC1belongs to hydrophilic protein, which has more hydrophilic region. The secondarystructure prediction of the protein was consisted of41%α helix, the folding of16.92%,41.85%curl.PsSOC1is belonged to the family of MADS-box gene that with typical MADS–box structure. qRT-PCRresults showed that PsSOC1may regulate the development of flower bud and gibberellins affect theexpression of PsSOC1.（4） PsCO is the upstream gene of PsFT, and it can regulate the expression of PsFT; while PsSOC1 is the downstream gene of PsFT, and PsFT can effect the expression of PsSOC1. The3genes could bewell studied the long-day photoperiod pathway of tree peony.