Gene expression analysis of volatile-rich male flowers of dioecious Pandanus fascicularis using expressed sequence tags

Pandanus fascicularis is dioecious with the female plant producing a non-scented fruit while the male produces a flower rich in volatiles. The essential oil extracted from the flowers is economically exploited as a natural flavouring agent as well as for its therapeutic properties. Molecular dissection of this distinct flower for identifying the genes responsible for its aroma by way of expressed sequence tags (ESTs) has not been initiated in spite of its economic viability. A male flower-specific cDNA library was constructed and 977 ESTs were generated. CAP3 analysis performed on the dataset revealed 83 contigs (549 ESTs) and 428 singlets, thereby yielding a total of 511 unigenes. Functional annotation using the BLAST2GO software resulted in 1952 Gene ontology (GO) functional classification terms for 621 sequences. Unknown proteins were further analysed with InterProScan to determine their functional motifs. RNA gel blot analysis of 26 functionally distinct transcripts potentially involved in flowering and volatile generation, using vegetative and reproductive tissues of both the sexes, revealed differential expression profiles. In addition to an overview of genes expressed, candidate genes with expression that are modulated predominantly in the male inflorescence were also identified. This is the first report on generation of ESTs to determine the subset of genes that can be used as potential candidates for future attempts aimed towards its genetic and genome analysis including metabolic engineering of floral volatiles in this economically important plant.