Final Report Summary - CARNIVOROM (Molecular basis of carnivory Excitability, movement, and endocrinology of plant traps) Carnivorous plants growing in nutrient-poor soils, such as the Venus flytrap Dionaea muscipula, depend on an animal diet. However, despite being known since Darwin’s time, the molecular basis of the carnivorous lifestyle remains largely unexplored. The “Carnivorom” project aimed to close this gap using a multidisciplinary approach based on state-of-art combination of genomics, bioinformatics, molecular biology, protein biochemistry and biophysics.Genome/Transcriptome Profiling: Although Dionaea shows the typical morphological and gross physiological properties of a green plant, it has evolved a highly specialized leaf-like structure – the snap trap. Profound morphological features enable the trap-forming leaf tip to catch and digest prey and, subsequently, the absorption of prey-derived nutrients. Because we assumed that these functional properties of the trap are based on the occurrence and abundance of specific transcript types, we generated a reference transcriptome of the Venus flytrap. In total, 1.43 billion reads were produced using high-throughput RNA sequencing on the Illumina HiSeq platform. Following assembly, correction and filtering, the final transcriptome of the Venus flytrap was shown to comprise 45,147 potential unigenes. An overall transcriptomic analyses revealed that Dionaea exhibits the typical genetic make-up of a flowering plant; no novel genes that could have led to the development of carnivory were identified. Furthermore, by comparing the transcriptomic profile of snap traps to that of other organs, we observed no specific signature of the insect capturing organ. Hence, we hypothesize that the carnivory-related functionalities of the trap rely most likely on a unique combination of genes also expressed in other organs. In line with this assumption, we found the multicellular glands that densely cover the inner surface of the trap dominate and shape the trap’s transcriptomic landscape. Once activated, these glands allow both prey digestion and nutrient uptake. Interestingly, active glands show all the signs of the stress responses typically associated with wounding and/or pathogen signalling in noncarnivorous plants. This includes the secretion of hydrolysing enzymes, ER-quality control and the generation of reactive oxygen species. Interestingly, and in contrast to noncarnivorous plants, Dionaea actively supresses programmed cell death (PCD) and activates nutrient transport.
