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An international team, including Rob Schuurink, Maaike Boersma, Tijs Bliek, Kees Spelt, Valentina Passeri, Ronald Koes and Francesca Quattrocchio (UvA Swammerdam Institute for Life Sciences) and colleagues of the Petunia Scientific Community, has completed the analysis of the genome of two parents of the garden petunia. The results were recently published in Nature Plants.

Petunias on Amsterdam bridge
Petunia's growing on an Amsterdam bridge. Courtesy of R. Koes and F. Quattrocchio

Petunia is a popular ornamental plant, present in gardens all over the world and every summer on the bridges of the Amsterdam canals. It is a largely used model system for molecular, biochemical, physiological and developmental research and the availability of its genome sequence represent a formidable improvement in the already well-equipped collection of genetic tools of this species.

Appearance of new species

The comparison of the genomes of the two wild species (Petunia axillaris and Petunia inflata) confirms that these are the two main contributors of the genome of the modern Petunia hybrida lines used in labs and in gardens all over the world. The comparison of the two genomes also offers the unique opportunity of looking at the evolution of traits that contributed to speciation in two species that separated relatively recently. Among these traits are those involved in the attraction of pollinators (e.g. scent production and flower pigmentation), as their differentiation contributes to genetic isolation and speciation.

Fast evolution

The genes encoding for master regulators of pigmentation, turned out to reside in hyper variable regions of the genome, subject to frequent events of rearrangement. This results in fast evolution, frequent acquisition of new expression patterns and the generation of different pigmentation patterns as observed in the two parents of petunia. The genes encoding for master regulators of pigmentation are also surrounded by hyper-variable genomic regions in the genome of other plants, suggesting that this mechanism was used over and over again and strongly contributed to the evolution of flowering plants by modulating ‘pollination syndromes’.

Petunia axillaris (left) and Petunia inflata (right)
Petunia axillaris (left) and Petunia inflata (right). Courtesy of R. Koes and F. Quattrocchio.

Petunia research

Genetic research using petunia as model was initiated in Amsterdam at the UvA in the 50’s by the group of Prof. Frans Bianchi. In the 80’s the group, at the time headed by Tom Gerats, moved to the VU together with a collection of mutants that greatly increased in the next decades. The collection of petunia lines and the research group, now under supervision of Ronald Koes, are back at the UvA since 2015. From the end of the 80’s the community of research groups using this small plant as model system grew to become a large consortium that now comprises researchers from all continents. The initiative to promote the sequencing of the genome was started in the group of Francesca Quattrocchio and Ronald Koes and was welcomed by the rest of the petunia community that brought it to completion without public funding.

Publication details

Bombarely et al. Insight into the evolution of the Solanaceae from the parental genomes of Petunia hybrida. Nature Plants(2016) DOI: 10.1038/nplants.2016.74.

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