• The Hawaiian Silversword alliance is a monophyletic group within the Asteraceae (sunflower family).

• This group has captured the attention of many researchers due to evidence of an allopolyploid event in their evolutionary history involving their diploid ancestors, Tarweeds1.

• This study compares the chloroplast genomes of Wilkesia gymnoxiphium (Silversword) and Centromadia parryi (Tarweed).

Methods

• Silversword leaf tissue was obtained from the University of California, Los Angeles, Mathias Botanical Garden for whole-genome sequencing. 

• To assemble the chloroplast genome, GetOrganelle version 1.7.7 was used with the genome sequencing reads as input2.

• The chloroplast genome assembly was inserted into Chlorobox GeSeq to generate the circular map3 and then again to generate the IRscope figure using IR+ for LSC, SSC, and IR region border position map4.

Figure 3: Comparison of Large Single Copy (LSC), Small Single Copy (SSC), and Inverted Repeat (IR) region border positions in chloroplast genomes of Solanum lycopersicum, Arabidopsis thaliana, Achyrachaena mollis, and Wilkesia gymnoxiphium using IRscope4.

Conclusions

•We assembled the first Wilkesia gymnoxiphium chloroplast genome.

•The chloroplast genomes remain largely conserved across Silversword and Tarweed species based on OGDRAW visual maps and IRscope comparison.

•Such cp genome conservation is consistent with past research1.

Future Research

•The lab is sequencing a genome in the  Anisocarpus genus, which is possibly closer to the ancestor. 

•Assemble chromosome-level genomes of Wilkesia and Anisocarpus for comparative genomics. 

•Comparison of chloroplast and mitochondrial genomes to learn more information on the evolutionary history of Silverswords and Tarweeds.

References

References: 1. Baldwin, B. G., Wood, K. R., & Freyman, W. A. (2021). Directionally biased habitat shifts and biogeographically informative cytonuclear discordance in the Hawaiian Silversword alliance (Compositae). American Journal of Botany, 108(10), 2015-2037. Software/Programs: 2. Tillich, M., Lehwark, P., Pellizzer, T., Ulbricht-Jones, E.S., Fischer, A., Bock, R., & Greiner, S. (2017). GeSeq – versatile and accurate annotation of organelle genomes. 3. Jin, J., Yu, W., Yang, J., Song, Y., dePamphilis, C.W., Yi, T., Li, D. (2020). GetOrganelle – a fast and versatile toolkit for accurate de novo assembly of organelle genomes. Genome Biology 21, 241. 4. Amiryousefi, A., Hyvönen, J., & Poczai, P. (2018). IRscope – An online program to visualize the junction sites of chloroplast genomes. Bioinformatics, 34(17), 3030-3031. Images: 5. Ueda, K.-I. (2017, September 3). [Centromadia parryi]. iNaturalist. 6. KarlM. (2009, December 10). [Iliau (Wilkesia gymnoxiphium) near the rim of Waimea Canyon, Kauaʻi.]. Wikipedia. 7. Kramer, N. (2011). [Centromadia parryi]. Center For Plant Conservation. 8. Hawai'i Division of Forestry and Wildlife. (2021, July 3). [Wilkesia gymnoxiphium]. OuterSpatial.