Abstract
We report the first plastome sequence of giant ragweed (Ambrosia trifida); with this new genome information, we assessed the phylogeny of Asteraceae and the transcriptional profiling against glyphosate resistance in giant ragweed. Assembly and genic features show a normal angiosperm quadripartite plastome structure with no signatures of deviation in gene directionality. Comparative analysis revealed large inversions across the plastome of giant ragweed and the previously sequenced members of the plant family. Asteraceae plastid genomes contain two inversions of 22.8 and 3.3 kb; the former is located between trnS-GCU and trnG-UCC genes, and the latter between trnE-UUC and trnT-GGU genes. The plastid genome sequences of A. trifida and the related species, Ambrosia artemisiifolia, are identical in gene content and arrangement, but they differ in length. The phylogeny is well-resolved and congruent with previous hypotheses about the phylogenetic relationship of Asteraceae. Transcriptomic analysis revealed divergence in the relative expressions at the exonic and intronic levels, providing hints toward the ecological adaptation of the genus. Giant ragweed shows various levels of glyphosate resistance, with introns displaying higher expression patterns at resistant time points after the assumed herbicide treatment.
Highlights
Plant invasions are accelerating on a global scale and cannot be fully understood without analyzing the genetic background of the source and invading populations
The rps12 gene was trans-spliced with the 5 end exon located in the LSC region and the two remaining exons found in the inverted repeat (IR) regions
The analysis presented here is an example of the use of herbarium genomics in other fields like weed research where, besides the biology of ragweeds, their control with herbicides is a major area of focus for research
Summary
Plant invasions are accelerating on a global scale and cannot be fully understood without analyzing the genetic background of the source and invading populations. Biological invasions may threaten both global and local biodiversity, ecosystem functions, agriculture, and public health (Vitousek et al, 1997). Human-induced global climate change might further complicate the effects of the invasions. In Europe, as in many other regions of the world, the number of invasive plant species has increased considerably in the past 200 years due to increased trade, tourism, and disturbance (Pyšek et al, 2009). Europe suffers from invasive species in many ways, and a crude estimate of monetary impact (diminished yield and control measures) suggests that these additional costs due to invasive species exceed €12 billion annually (Kettunen et al, 2009), this may be an underestimate (Vilá et al, 2010).
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