Transcriptome and Genome of the Venus Flytrap

Darwin was fascinated by the unusual adaptations of carnivorous plants during his often frustrating studies of the evolution of flowering plants, which he referred to as an ‘abominable mystery’. Darwin’s treatise on insectivorous plants noted that the Venus flytrap (Dionaea muscipula) was ‘one of the most wonderful of the world’. Studies of carnivorous plants have continued since Darwin’s time.

An understanding of the molecular adaptations to plant carnivory has also been sought via genome size estimates. Genome sizes vary more than 2,300-fold among angiosperms, from that of Paris japonica (~149 Gbp) to that of carnivorous Genlisea margaretae (~63 Mbp). The biological significance of this massive variation is puzzling.

A new paper in PLOS ONE examines the transcriptome and genome of the Venus flytrap, Dionaea muscipula. The transcriptome provides some insight into the molecular processes occurring in a Gb-sized carnivorous plant genome. Abundant representation of processes related to the expression of genes associated with catalytic, antioxidant and electron carrier activities was observed. Future uniform meta-analyses of short-read archives, including cDNA sequences from carnivorous Utricularia and Sarracenia species will aid studies of carnivorous plants and their ecology. This underlines the importance of further expansion of sequence repositories, especially for non-model organisms, for improved understanding of molecular physiology and evolution related to Darwin’s ‘abominable mystery’.

Jensen MK, Vogt JK, Bressendorff S, Seguin-Orlando A, Petersen M, et al. (2015) Transcriptome and Genome Size Analysis of the Venus Flytrap. PLoS ONE 10(4): e0123887. doi:10.1371/journal.pone.0123887
Abstract
The insectivorous Venus flytrap (Dionaea muscipula) is renowned from Darwin’s studies of plant carnivory and the origins of species. To provide tools to analyze the evolution and functional genomics of D. muscipula, we sequenced a normalized cDNA library synthesized from mRNA isolated from D. muscipula flowers and traps. Using the Oases transcriptome assembler 79,165,657 quality trimmed reads were assembled into 80,806 cDNA contigs, with an average length of 679 bp and an N50 length of 1,051 bp. A total of 17,047 unique proteins were identified, and assigned to Gene Ontology (GO) and classified into functional categories. A total of 15,547 full-length cDNA sequences were identified, from which open reading frames were detected in 10,941. Comparative GO analyses revealed that D. muscipula is highly represented in molecular functions related to catalytic, antioxidant, and electron carrier activities. Also, using a single copy sequence PCR-based method, we estimated that the genome size of D. muscipula is approx. 3 Gb. Our genome size estimate and transcriptome analyses will contribute to future research on this fascinating, monotypic species and its heterotrophic adaptations.