Abstract:

One ubiquitin protein gene was obtained from tree peony（Paeonia suffruticosa‘Luoyanghong’）by RT-PCR. It was designated as PsUBI and the GenBank accession number was KP742952. The open reading frame（ORF）of PsUBI was 447 bp，and could encode 148 amino acids.Homologous alignment shows that it shared over 81% nucleotide sequence similarity and over 96% amino acid sequence similarity with ubiquitins in other plants. The phylogenetic tree analysis suggested that the relationship of ubiquitin between P. suffruticosa and Gossypium hirsutum was close，based on the amino acid sequences. Real time quantitative PCR analysis revealed that compared to other five commonly used housekeeping genes（GAPDH，GAPDH1，tubulin，tubulin2，18S rRNA），ubiquitin has the most constant CT values of PCR amplification curve in different tissues of tree peony，especially in floral organs. Further analysis of the results showed that PsUBI was constantly expressed in various organs of tree peony such as roots，stems，leaves，petals，stamens and carpels，especially in floral organs. We used ubiquitin as the reference gene，and found that the expression pattern of PsAG in floral organs of tree peony was consistent with its action sites. Thus，PsUBI can be more appropriate for floral organ study of tree peony.

Key words: tree peony, ubiquitin, gene clone, expression analysis, reference gene