Hybridization and Polyploidy – Major Factors in Angiosperm Evolution: a Case Study of Nicotiana (Solanceae)
Hybridisation and polyploidy have been major factors in angiosperm evolution; to study these phenomena, case studies must be undertaken, and the focus in this instance is the genus Nicotiana (Solanaceae).
Nicotiana (Solaceae) is a genus of about 75 species, 40% of which are allotetraploids. In addition, several species are homoploid (diploid) hybrids. This high frequency of hybridization and polyploidy make the genus ideal for studying how these phenomena have contributed to the evolutionary success of the genus and in particular, how these have altered their genome structure and content. We started with a series of phylogenetic studies of plastid and nuclear loci to determine parentage of hybrids; while this work was progressing we studied as well how higher-copy parts of their genomes were reorganized during the process of diploidisation, which always follows an increase in ploidy in angiosperms and eventually results in chromosome reorganisation and reduction. Studies have also included genome size estimation, FISH (fluorescent in-situ hybridization), GISH (genomic in-situ hybridization) and artificial crosses to putatively remake natural hybrids. Several parts of this project have been supported by grants from NERC (UK; see below). Our results have been published in several high-profile journals and have led to an improved understanding of angiosperm evolution and their genome structure.
Key publications 2006-2011
- Clarkson, J.J., Kelly, L.J., Leitch, A.R., Knapp, S. & Chase, M.W. (2010). Nuclear glutamine synthetase evolution in Nicotiana: phylogenetics and the origins of allotetraploid and homoploid (diploid) hybrids. Molecular Phylogentics and Evolution 55: 95-112.
- Kelly, L.J., Leitch, A.R., Clarkson, J.J., Knapp, S. & Chase, M.W. (2010). Intragenic recombination events and evidence for hybrid speciation in Nicotiana (Solanaceae). Molecular Biology and Evolution 27: 781-799.
- Leitch, I.J., Hanson, L., Lim, K.Y., Kovarik, A., Chase, M.W., Clarkson, J.J. & Leitch, A.R. (2008). The ups and downs of genome size evolution in polyploidy species of Nicotiana (Solanaceae). Annals of Botany 101: 805-814.
- Yoong, K.Y., Kovarik, A., Matyasek, R., Chase, M.W., Clarkson, J.J., Grandbastien, M.A. & Leitch, A.R. (2007). Sequence of events leading to near-complete genome turnover in allopolyploid Nicotiana within five million years. New Phytologist 175: 756-763.
- Lim Y., Leitch, A.R., Skalicka, K., Sarasan, V., Clarkson, J.J. Chase, M.W. & Kovarik. A. (2006). A genetic appraisal of new synthetic Nicotiana tabacum and Kostoff (1938) artificial tobacco. American Journal of Botany 93: 875-883.
Project partners and collaborators
A. Kovarik (Czech Academy of Sciences)
M.-A. Grandbastien (INRA, Versailles)
Sandy Knapp, (NHM London)
Andrew Leitch, Y. Kim (University of London)
NERC (Natural Environment Research Council) “Genome evolution in allopolyploid plants”, co-investigator with A. R. Leitch and Y. Lim (Queen Mary and Westfield College), £344,056 (March 2005 – February 2008).