Complete plastome sequence of Nepenthes mirabilis (Nepenthaceae): a "vulnerable" herb in China

Draft genome and transcriptome of Nepenthes mirabilis, a carnivorous plant in China

OBJECTIVES

Nepenthes belongs to the monotypic family Nepenthaceae, one of the largest carnivorous plant families. Nepenthes species show impressive adaptive radiation and suffer from being overexploited in nature. Nepenthes mirabilis is the most widely distributed species and the only Nepenthes species that is naturally distributed within China. Herein, we reported the genome and transcriptome assemblies of N. mirabilis. The assemblies will be useful resources for comparative genomics, to understand the adaptation and conservation of carnivorous species.

DATA DESCRIPTION

This work produced ~ 139.5 Gb N. mirabilis whole genome sequencing reads using leaf tissues, and ~ 21.7 Gb and ~ 27.9 Gb of raw RNA-seq reads for its leaves and flowers, respectively. Transcriptome assembly obtained 339,802 transcripts, in which 79,758 open reading frames (ORFs) were identified. Function analysis indicated that these ORFs were mainly associated with proteolysis and DNA integration. The assembled genome was 691,409,685 bp with 159,555 contigs/scaffolds and an N50 of 10,307 bp. The BUSCO assessment of the assembled genome and transcriptome indicated 91.1% and 93.7% completeness, respectively. A total of 42,961 genes were predicted in the genome identified, coding for 45,461 proteins. The predicted genes were annotated using multiple databases, facilitating future functional analyses of them. This is the first genome report on the Nepenthaceae family.

Omics Approaches in Uncovering Molecular Evolution and Physiology of Botanical Carnivory

Systems biology has been increasingly applied with multiple omics for a holistic comprehension of complex biological systems beyond the reductionist approach that focuses on individual molecules. Different high-throughput omics approaches, including genomics, transcriptomics, metagenomics, proteomics, and metabolomics have been implemented to study the molecular mechanisms of botanical carnivory. This covers almost all orders of carnivorous plants, namely Caryophyllales, Ericales, Lamiales, and Oxalidales, except Poales. Studies using single-omics or integrated multi-omics elucidate the compositional changes in nucleic acids, proteins, and metabolites. The omics studies on carnivorous plants have led to insights into the carnivory origin and evolution, such as prey capture and digestion as well as the physiological adaptations of trap organ formation. Our understandings of botanical carnivory are further enhanced by the discoveries of digestive enzymes and transporter proteins that aid in efficient nutrient sequestration alongside dynamic molecular responses to prey. Metagenomics studies revealed the mutualistic relationships between microbes and carnivorous plants. Lastly, in silico analysis accelerated the functional characterization of new molecules from carnivorous plants. These studies have provided invaluable molecular data for systems understanding of carnivorous plants. More studies are needed to cover the diverse species with convergent evolution of botanical carnivory.

Plastid Genomes of Carnivorous Plants Drosera rotundifolia and Nepenthes × ventrata Reveal Evolutionary Patterns Resembling Those Observed in Parasitic Plants

Carnivorous plants have the ability to capture and digest small animals as a source of additional nutrients, which allows them to grow in nutrient-poor habitats. Here we report the complete sequences of the plastid genomes of two carnivorous plants of the order Caryophyllales, Drosera rotundifolia and Nepenthes × ventrata. The plastome of D. rotundifolia is repeat-rich and highly rearranged. It lacks NAD(P)H dehydrogenase genes, as well as ycf1 and ycf2 genes, and three essential tRNA genes. Intron losses are observed in some protein-coding and tRNA genes along with a pronounced reduction of RNA editing sites. Only six editing sites were identified by RNA-seq in D. rotundifolia plastid genome and at most conserved editing sites the conserved amino acids are already encoded at the DNA level. In contrast, the N. × ventrata plastome has a typical structure and gene content, except for pseudogenization of the ccsA gene. N. × ventrata and D. rotundifolia could represent different stages of evolution of the plastid genomes of carnivorous plants, resembling events observed in parasitic plants in the course of the switch from autotrophy to a heterotrophic lifestyle.