Rapid generation and analysis of expressed sequence tags to uncovering inflorescence secondary metabolism of Bougainvillea spectabilis ‘Speciosas’ by pyrosequencing

Abstract

Bougainvilleas, are one of the unique plant families with an unusual class of pigments, known as betalains replaced the more common anthocyanins. However, little is known on the molecular mechanism on the mutual exclusion of anthocyanins and betalains. In order to explore the unique phenomena in Bougainvilleas, we used open inflorescences of B. spectabilis ‘Speciosas’ for transcriptome analysis by pyrosequencing, which is the first attempt to obtain the transcriptome of this specific plant. In this study, we obtained 111.9 M raw data, after assembling, 17,728 unigenes sequence with average length of 607 bp long were available, the annotation including Gene Ontology, COG/KOG and associated Kyoto Encyclopedia of Genes and Genomics (KEGG) pathway maps were conducted. Important genes involved in flavonoid/Betalains/anthocyanins motablisms were identified including FLS/F3H, UGT, DFR, DODA, anthocyanidin reductase and Anthocyanidin 3-O-glucosyltransferase, as well as some transcriptional factors (Myb, YABBY, MADS-box, F-box, WD-40 and bHLH) in this study. The obtained unigenes which will provide a database for discovering genes involved in secondary metabolic synthesis pathway. The discovered genes can be used for future bioengineering of various secondary metabolites for health improvement, pigments, medicine and agricultural production, etc. Specially, these genes such as DFR, anthocyanidin reductase and anthocyanidin 3-O-glucosyltransferase, were detected in betalain-synthesizing plants, which is exciting for researchers. Furthermore, a total of 877 simple sequence repeat motifs (SSRs) were identified, among the perfect SSRs, the most abundant repeat units were mononucleotide repeats (61 %) with (A/T)n and the second one is tri-nucleotide repeats (24 %). The obtained EST-SSRs can be used for marker development which will be beneficial for the studies in the aspects of genetic diversity, evolution and phenotype variation of B. spectabilis ‘Speciosas’ as well as its related species.