Functional annotation of expressed sequence tags as a tool to understand the molecular mechanism controlling flower bud development in tree peony

Tree peony (Paeonia suffruticosa Andrews) is an important medicinal and ornamental plant. In China, its root bark is an important ingredient for traditional Chinese medicine. It is valued as an ornamental plant because its flower shows a wide variation in shape and color. We used flower buds at different developmental stages to construct the first cDNA library for this organism. A total of 2241 raw expressed sequence tags (ESTs) were obtained after unidirectional sequencing. After processing and assembly, they resulted in a total of 1300 unigenes [363 contigs with an average size of 3.5 ESTs (ranging from 2 up to 36) and 937 singletons]. Gene Ontology categories were assigned and further summarized into 13 broad families with biological roles according to similar functional characteristics or cellular roles. A total of 185 single nucleotide polymorphisms were detected for all contigs. We were able to detect open reading frames in the consensus sequences of 1268 unigenes. 97.5% of the ESTs showed significant similarity to sequences present in public databases. One hundred and sixty-seven short sequence repeats were obtained in the whole data set. All the analysis and information will be valuable resources for a better understanding of this important plant and also can be used for functional study in Paeoniaceae.