Abstract
Invasive species are a major threat to global biodiversity but can also serve as valuable model systems to examine important evolutionary processes. While the ecological aspects of invasions have been well documented, the genetic basis of adaptive change during the invasion process has been hampered by a lack of genomic resources for the majority of invasive species. Here we report the first larval transcriptomic resource for the Northern Pacific Seastar, Asterias amurensis, an invasive marine predator in Australia. Approximately 117.5 million 100 base-pair (bp) paired-end reads were sequenced from a single RNA-Seq library from a pooled set of full-sibling A. amurensis bipinnaria larvae. We evaluated the efficacy of a pre-assembly error correction pipeline on subsequent de novo assembly. Error correction resulted in small but important improvements to the final assembly in terms of mapping statistics and core eukaryotic genes representation. The error-corrected de novo assembly resulted in 115,654 contigs after redundancy clustering. 41,667 assembled contigs were homologous to sequences from NCBI’s non-redundant protein and UniProt databases. We assigned Gene Ontology, KEGG Orthology, Pfam protein domain terms and predicted protein-coding sequences to > 36,000 contigs. The final transcriptome dataset generated here provides functional information for 18,319 unique proteins, comprising at least 11,355 expressed genes. Furthermore, we identified 9,739 orthologs to P. miniata proteins, evaluated our annotation pipeline and generated a list of 150 candidate genes for responses to several environmental stressors that may be important for adaptation of A. amurensis in the invasive range. Our study has produced a large set of A. amurensis RNA contigs with functional annotations that can serve as a resource for future comparisons to other echinoderm transcriptomes and gene expression studies. Our data can be used to study the genetic basis of adaptive change and other important evolutionary processes during a successful invasion.
Highlights
Invasive species occupy areas outside their historical range and often experience novel environmental conditions [1,2] that may result in strong selection on morphological and physiological traits [3]
A cDNA library was constructed for the mid-bipinnaria larval stage of A. amurensis
Quality control resulted in the removal of 26.9% of raw sequence reads leaving 35,078,206 pairs and 15,761,360 orphan reads, from which 1.28 × 109 bases were removed during GC-content bias trimming
Summary
Invasive species occupy areas outside their historical range and often experience novel environmental conditions [1,2] that may result in strong selection on morphological and physiological traits [3]. Research has documented that adaptive change in response to novel environments is common during the invasion process [4,5,6]. The source of genetic or epigenetic variation underlying adaptive change during the invasion process remains largely uncharacterised [2,7], which has occurred in part, due to a lack of genomic information. Transcriptome resources have helped reveal substantial shifts in the expression of metabolism and cellular repair genes which may contribute to the increased dispersal ability of invasion front cane toads (Rhinella marina) [16]. Gene expression data can provide valuable information to understand important evolutionary processes in invasion biology, especially because it links observable genetic changes to functional roles
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