Mapping podophyllotoxin biosynthesis and growth-related transcripts with high elevation in Sinopodophyllum hexandrum

Sinopodophyllum hexandrum, a perennial rhizomatous herb that produces the anti-cancer metabolite podophyllotoxin (PPT), is distributed in the Himalayan region. While greater plant growth and PPT accumulation is observed at higher compared with lower elevations, the mechanism responsible for elevation-dependent growth promotion and PPT biosynthesis has not been reported. Here, the de novo sequenced transcriptome of S. hexandrum is described. When plants were grown at 3300 versus 2300 m above sea level (asl), a total of 53,691 unigenes were generated and 736 differentially expressed genes (DEGs) were observed. DEGs (357) were identified with 234 characterized genes showing greater up than down regulation, 171 versus 63, respectively. Functional annotation classified 23 DEGs involved in PPT biosynthesis, including phenylpropanoid enzymes: phenylalanine ammonia layse (PAL), cinnamyl alcohol-dehydrogenase (CAD), dirigent protein (DIR), pinoresinol-lariciresinol reductase (PLR), CYP719A23, CYP71CU1, and 2-oxoglutarate/Fe(II)-dependent dioxygenase (2-ODD) which directly participate in PPT biosynthesis. Over 200 DEGs that participate in plant growth and development are categorized into: cell morphogenesis, bio-signaling, primary metabolism, photosynthesis/energy, transcription/polynucleotide metabolism, translation/protein synthesis, transport, and stress tolerance. This transcriptomic analysis provides insight into the mechanism that enhances plant growth and PPT accumulation in S. hexandrum under higher elevation conditions.