Genomic Studies in Angiosperms
This project aims to investigate the causes, consequences and evolutionary significance of the striking genome diversity encountered in angiosperms.
Sites of recombination between Gasteria and Aloe genomes in the progeny of an Aloe x Gasteria hybrid. Gasteria chromosomes are painted yellow following hybridization with fluorescently labelled genomic DNA from Gasteria. Aloe chromosomes are stained red.
There is a huge diversity in the genomic structure and organization of angiosperm genomes. This diversity is seen at many levels ranging from the variation in DNA sequences, the number and organization of chromosomes comprising the genome, the number and origin of genomes (ploidy) and the amount of DNA within the nucleus (genome size) (1C-values range 67 – 150,000 Mb). Using key cytological research techniques and in collaboration with other researchers (both internal and external), the origin and evolutionary significance of this striking genome diversity is being studied in selected plant groups within a robust phylogenetic framework and making use of the extensive plant collections at Kew. (Genomic studies on monocot groups are covered in more detail in the project ‘Genomic studies in monocots’).
Some of the key research techniques being employed and their application are listed below:
- Classical cytogenetic techniques are used to count and characterise chromosome morphology, including C-banding. A chromosome count exists for only about 25% of angiosperm species. Yet even this information is incomplete or incorrect for many species as many counts are reported from just one individual and many species may be incorrectly named. There are clearly still major gaps in our knowledge of this gross karyotypic character.
- Various types of fluorescent in situ hybridization approaches including comparative chromosome painting are employed to determine how particular DNA sequences are organised along chromosomes and how whole genomes are organised in hybrid and polyploid species.
- Feulgen microdensitometry and flow cytometry are used to estimate genome size. Genome size is a key biodiversity character of fundamental biological significance. Although genome sizes are currently available for only c. 1.5% of angiosperm species they vary by nearly 2400-fold. Filling key gaps in genome size data and carrying out large scale comparative studies to enable the evolutionary significance of this immense variation to be understood is part of an ongoing project. Collating and disseminating plant genome size data is covered by the project entitled ‘Plant DNA C-values database’.
- Molecular sequencing tools are being increasingly used for characterising the evolution of some of the numerous repetitive DNA sequences that make up the bulk of many genomes. Current work is focusing on the evolution and organization of DNA satellite sequences and retrotransposons in the Asparagales (including Orchidaceae) and Liliales, two of the orders with the greatest range of genome size.
Data generated from all these approaches are integrated to gain greater understanding of the principles, processes and phenomena operating at different genomic levels which create and control plant biodiversity.
Over the past five years, the team has (i) published several research papers per year in international journals (including many in journals of impact factor >2), (ii) organized a symposium entitled ‘Plant Genome Horizons – Vistas and Visions’ and (iii) successfully raised funds from the Research Council of Norway to investigate the role of phosphate in the evolution of genome size diversity - a collaborative project with the University of Oslo.
Project Leader: Leitch, Ilia J.
Mike Fay, Lynda Hanson, Jeffrey Joseph, Laura Kelly, Ralf G. Kynast, Ilia Leitch, Jaume Pellicer
Project Partners and Collaborators
Institute of Plant Molecular Biology, Ceske Budejovice
Department of Functional Genomics and Proteomics, University of Masaryk, Brno
Charles University, Prague
Dept. of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo
Queen Mary, University of London
Imperial College, London
Research Council of Norway (Genome size and phosphate)
Key publications 2006-2011
Leitch, A.R. & Leitch, I.J. (2008). Genomic plasticity and the diversity of polyploid plants. Science 320: 481-483.
Lysák, M.A., Koch, M.A., Beaulieu, J.M., Meister, A.,& Leitch, I.J. (2009). The dynamic ups and downs of genome size evolution in Brassicaceae. Molecular Biology and Evolution 26: 85-98.
Papadopulos, A.S.T., Baker, W.J., Crayn, D., Butlin, R.K., Kynast, R.G., Hutton, I. & Savolainen, V. (2011). Speciation with gene flow on Lord Howe Island. Proceedings of the National Academy of Sciences of the United States of America 108: 13188-13193.
Kelly, L.J., Leitch, A.R., Clarkson ,J.J., Hunter, R.B., Knapp, S. & Chase, M.W. (2010). Intragenic recombination events and evidence for hybrid speciation in Nicotiana (Solanaceae). Molecular Biology and Evolution 27(4): 781-799.
Kejnovsky, E., Leitch, I.J. & Leitch, A.R. (2009). Contrasting evolutionary dynamics between angiosperm and mammalian genomes. Trends in Ecology & Evolution 24(10): 572-582.