@article{c715fba00b1c40b48ab7db3c3168599e,
title = "Dual-species origin of an adaptive chemical defense polymorphism",
abstract = "Allopolyploid speciation and chemical defense diversification are two of the most characteristic features of plant evolution; although the former has likely shaped the latter, this has rarely been documented. Here we document allopolyploidy-mediated chemical defense evolution in the origin of cyanogenesis (HCN release upon tissue damage) in white clover (Trifolium repens). We combined linkage mapping of the loci that control cyanogenesis (Ac, controlling production of cyanogenic glucosides; and Li, controlling production of their hydrolyzing enzyme linamarase) with genome sequence comparisons between white clover, a recently evolved allotetraploid, and its diploid progenitors (Trifolium pallescens, Trifolium occidentale). The Ac locus (a three-gene cluster comprising the cyanogenic glucoside pathway) is derived from T. occidentale; it maps to linkage group 2O (occidentale subgenome) and is orthologous to a highly similar cluster in the T. occidentale reference genome. By contrast, Li maps to linkage group 4P (pallescens subgenome), indicating an origin in the other progenitor species. These results indicate that cyanogenesis evolved in white clover as a product of the interspecific hybridization that created the species. This allopolyploidization-derived chemical defense, together with subsequent selection on intraspecific cyanogenesis variation, appears to have contributed to white clover{\textquoteright}s ecological success as a globally distributed weed species.",
keywords = "Trifolium repens (Fabaceae), allopolyploid speciation, chemical defense, cyanogenic glucoside, intraspecific polymorphism, linamarase",
author = "Olsen, {Kenneth M.} and Goad, {David M.} and Wright, {Sara J.} and Dutta, {Maya L.} and Myers, {Samantha R.} and Small, {Linda L.} and Li, {Lin Feng}",
note = "Funding Information: The authors thank Mike Dyer and other staff of the Washington University greenhouse facility for providing plant care; Andrew Griffiths and Roger Moraga (AgResearch NZ) for reference genome sequence information; Rachel Tan (AgResearch NZ) and Jennifer Barrett (Danforth Plant Science Center, St Louis) for guidance on genotyping-by-sequencing protocols; Marshall Wedger (Washington University) for assistance with QTL mapping scripts; and members of the Olsen lab group for helpful comments on the manuscript. Funding for the work was provided by NSF grants IOS-1557770 to KMO and DEB-1601641 to SJW, and by NSF graduate research fellowship DGE-1143954 to SJW. The authors declare no competing interests. Funding Information: The authors thank Mike Dyer and other staff of the Washington University greenhouse facility for providing plant care; Andrew Griffiths and Roger Moraga (AgResearch NZ) for reference genome sequence information; Rachel Tan (AgResearch NZ) and Jennifer Barrett (Danforth Plant Science Center, St Louis) for guidance on genotyping‐by‐sequencing protocols; Marshall Wedger (Washington University) for assistance with QTL mapping scripts; and members of the Olsen lab group for helpful comments on the manuscript. Funding for the work was provided by NSF grants IOS‐1557770 to KMO and DEB‐1601641 to SJW, and by NSF graduate research fellowship DGE‐1143954 to SJW. The authors declare no competing interests. Publisher Copyright: {\textcopyright} 2021 The Authors. New Phytologist {\textcopyright} 2021 New Phytologist Foundation",
year = "2021",
month = nov,
doi = "10.1111/nph.17654",
language = "English",
volume = "232",
pages = "1477--1487",
journal = "New Phytologist",
issn = "0028-646X",
number = "3",
}