de novo Transcriptome Analysis Reveals the Molecular Components of Floral Scent Production in Thermogenic Arum concinnatum

Among the large number of poikilothermic plant species, several can raise their internal body temperature to a level higher than the ambient temperature to attract insect pollinators by volatilizing floral scent compounds. Among thermogenic plants, Arum concinnatum shows the highest respiration activity during thermogenesis. However, an overall understanding of the genes related to plant thermogenesis has not yet been achieved. In this study, to develop a global view of the transcriptome underlying thermogenesis and to elucidate the genes involved in heat production, we performed de novo transcriptome analysis of the flower organs in thermogenic plant A. concinnatum. The de novo transcriptome assembly represented, in total, 158,490 non-redundant transcripts, and 53,315 of those showed significant homology with known genes. To explore genes associated with thermogenesis, we filtered 1266 transcripts that showed a significant correlation between expression pattern and the temperature trend of each sample. As expected, we confirmed five putative alternative oxidase transcripts, a well-known key player of thermogenesis in plant, were included in filtered transcripts. An enrichment analysis of the Gene Ontology terms for the filtered transcripts suggested over-representation of genes involved in 1-deoxy-D-xylulose-5-phosphate synthase (DXS) activity. The expression profiles of DXS transcripts in the methyl-D-erythritol 4-phosphate (MEP) pathway were significantly correlated with thermogenic levels. Our results suggest that the MEP pathway is the main biosynthesis route for producing scent monoterpenes in A. concinnatum. To the best of our knowledge, this is the first report describing the candidate pathway and the key enzyme for floral scent production in thermogenic plants.