Abstract
BackgroundSinopodophyllum hexandrum is an endangered medicinal herb, which is commonly present in elevations ranging between 2,400–4,500 m and is sensitive to temperature. Medicinal property of the species is attributed to the presence of podophyllotoxin in the rhizome tissue. The present work analyzed transcriptome of rhizome tissue of S. hexandrum exposed to 15°C and 25°C to understand the temperature mediated molecular responses including those associated with podophyllotoxin biosynthesis.ResultsDeep sequencing of transcriptome with an average coverage of 88.34X yielded 60,089 assembled transcript sequences representing 20,387 unique genes having homology to known genes. Fragments per kilobase of exon per million fragments mapped (FPKM) based expression analysis revealed genes related to growth and development were over-expressed at 15°C, whereas genes involved in stress response were over-expressed at 25°C. There was a decreasing trend of podophyllotoxin accumulation at 25°C; data was well supported by the expression of corresponding genes of the pathway. FPKM data was validated by quantitative real-time polymerase chain reaction data using a total of thirty four genes and a positive correlation between the two platforms of gene expression was obtained. Also, detailed analyses yielded cytochrome P450s, methyltransferases and glycosyltransferases which could be the potential candidate hitherto unidentified genes of podophyllotoxin biosynthesis pathway.ConclusionsThe present work revealed temperature responsive transcriptome of S. hexandrum on Illumina platform. Data suggested expression of genes for growth and development and podophyllotoxin biosynthesis at 15°C, and prevalence of those associated with stress response at 25°C.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-871) contains supplementary material, which is available to authorized users.
Highlights
Sinopodophyllum hexandrum is an endangered medicinal herb, which is commonly present in elevations ranging between 2,400–4,500 m and is sensitive to temperature
Rhizome biology for S. hexandrum is of interest that rhizome is the source of medicinally important compound podophyllotoxin, and it allows plant to survive the unfavorable environment of winters when aerial portion of the plant dies
Availability of vast genomic and transcriptomic data in the public domain coupled with generation sequencing platforms made it possible to understand temperature responsive biology of rhizome of S. hexandrum
Summary
Sinopodophyllum hexandrum is an endangered medicinal herb, which is commonly present in elevations ranging between 2,400–4,500 m and is sensitive to temperature. Medicinal property of the species is attributed to the presence of podophyllotoxin in the rhizome tissue. The present work analyzed transcriptome of rhizome tissue of S. hexandrum exposed to 15°C and 25°C to understand the temperature mediated molecular responses including those associated with podophyllotoxin biosynthesis. Like other alpine plant species [6], S. hexandrum has been reported to be sensitive to high temperature [7]. Higher temperature was reported to increase the transpiration rate and reduce water use efficiency indicating the species to be sensitive at high temperature [8]. The species did not survive for long at 10°C and 35°C
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