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. 2011 Aug;18(4):253-61.
doi: 10.1093/dnares/dsr014. Epub 2011 Jun 15.

Transcriptome Analysis of Sarracenia, an Insectivorous Plant

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Free PMC article

Transcriptome Analysis of Sarracenia, an Insectivorous Plant

Anuj Srivastava et al. DNA Res. .
Free PMC article

Abstract

Sarracenia species (pitcher plants) are carnivorous plants which obtain a portion of their nutrients from insects captured in the pitchers. To investigate these plants, we sequenced the transcriptome of two species, Sarracenia psittacina and Sarracenia purpurea, using Roche 454 pyrosequencing technology. We obtained 46 275 and 36 681 contigs by de novo assembly methods for S. psittacina and S. purpurea, respectively, and further identified 16 163 orthologous contigs between them. Estimation of synonymous substitution rates between orthologous and paralogous contigs indicates the events of genome duplication and speciation within the Sarracenia genus both occurred ∼2 million years ago. The ratios of synonymous and non-synonymous substitution rates indicated that 491 contigs have been under positive selection (K(a)/K(s) > 1). Significant proportions of these contigs were involved in functions related to binding activity. We also found that the greatest sequence similarity for both of these species was to Vitis vinifera, which is most consistent with a non-current classification of the order Ericales as an asterid. This study has provided new insights into pitcher plants and will contribute greatly to future research on this genus and its distinctive ecological adaptations.

Figures

Figure 1.
Figure 1.
A bar plot showing the hits (blastx top hit) to previously sequenced species (displaying only top five species) for S. psittacina and S. purpurea contigs.
Figure 2.
Figure 2.
A bar plot showing the Blast2GO functional assignments in three GO categories: (A) biological process, (B) molecular function, and (C) cellular component for S. psittacina and S. purpurea contigs.
Figure 3.
Figure 3.
A bar plot displaying the proportion of contigs mapped to a particular region of Vitis genome in two species.
Figure 4.
Figure 4.
A Venn diagram showing the count of orthologous and unique contigs between two species.
Figure 5.
Figure 5.
A scatter plot of the Ka/Ks ratio for 491 orthologous contigs under diversifying selection. Contigs with Ka/Ks > 1 fall above the light grey line and >2 values fall above the black line.
Figure 6.
Figure 6.
Ks value distribution between the two Sarracenia species for the identification of the genome duplication event and the speciation event. (A) The secondary peak (Ks = 0.03) in the paralogous Ks distribution indicates the genome duplication. (B) The secondary peak (Ks = 0.03) in the orthologous Ks distribution give the indication of speciation event.

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References

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