Unravelling the genes responsible for life history traits in the giant woody cabbage (Brassica oleracea)
Which genes are involved in woodiness and associated traits such as drought stress resistance, flowering time, stem elongation, life span, and plant herbivory, and how do these QTLs overlap?
- F.P. Lens
- Naturalis Biodiversity Center
- Plant Ecology and Phytochemistry
When herbs and trees germinate, they both start from a tiny seedling, which develops into a small non-woody mature plant in the former and into a woody giant in the latter. To this day, scientists have failed to provide satisfying answers why and how these contrasting life forms have evolved. We have crossed a giant woody, late flowering cabbage accession (Jersey kale) with a small, rapid flowering cabbage accession (TO1000) belonging to the same species (Brassica oleracea), and created 196 F2 genotypes. In this F2 population, the contrasting features of the grandparents are segregating, such as woodiness, drought stress resistance, flowering time, developmental speed, stem elongation, life span, and plant herbivory resistance. This allows us to find Quantitative Trait Loci (QTLs) for these traits. These QTLs make it possible to detect connection between these traits at the genetic level, and they present the first step in the discovery of the underlying genes.
An ongoing global derived woodiness database has revealed hundreds of independent evolutionary transitions from herbaceousness towards derived woodiness in flowering plants, and highlights that most of these woody species occur in continental regions with a marked drought period (F. Lens, unpublished data). This links the evolution of derived woodiness to drought, which has led to a novel hypothesis why plants would become woody during evolutionary history. Brassicaceae comprise about 100 transitions towards woody species native to contrasting environments, making the family an excellent model group to investigate (1) the link between woodiness and drought stress and other co-evolving life history features, and (2) to explore the genetic mechanism behind the traits of interest across this set of 100 independent phylogenetic sister groups.
We have set up a tissue culture line of a cross consisting of the Jersey kale – a giant woody, late-flowering, walking stick cabbage, with TO1000 – a small, rapid flowering accession belonging to the same species (Brassica oleracea). The F1 generation is similar in growth form, but shows more than six months difference in flowering time, owing to the heterozygosity of the Jersey kale parent. The reciprocal cross of an early and a late flowering F1 has been carried out, and we are observing that the contrasting features of the grandparents, such as woodiness and flowering time, are segregating in the F2 population. We are currently phenotyping these characters, together with traits related to drought stress resistance, developmental speed, stem elongation, life span, and plant herbivory.
A more in-depth SNP calling of the parents is on its way, necessary to complete the genetic map based on the F2 individuals. This opens new opportunities to dig deeper into the genetic mechanism leading to the traits of interest, and assess the level of overlap at the genetic level.
People with complementary expertise are welcome to join this project. Please contact one of the coordinators.
MSc thesis Dymphe Remarque:
My MSc project aims to find Quantitative Trait Loci (QTLs) for traits of the F2 population belonging to six categories that are generated by myself and by the other projects that are currently carried out: general plant morphology, chlorophyll concentration in leaves, herbivory resistance, flowering time and flower colour, drought resistance, and endophyte presence in roots. The phenotyping is being done for 192 F2 genotypes. In addition, a genetic map with markers at regular intervals will be constructed by screening the parental plant genomes for Single Nucleotide Polymorphisms (SNPs). Compiling all these data will enable us to find out what the overlap is of the genetic mechanism of woodiness, drought stress resistance and flowering time, three traits that are hypothesized to be linked to each other.
MSc thesis Jesse van Haasteren:
I want to assess what causes the differences in water-use behavior and hydraulic traits related to drought resistance in the 200 genotypes of the F2 population in Brassica oleracea. Therefore, a range of hydraulic, physiological and anatomical traits will be measured before, during and after a drought treatment on all the genotypes. Investigating these measurements will help us understand whether woodiness is linked to drought in Brassica oleracea and how we could translate this knowledge into increased drought resistance of future crops.
MSc thesis Laurens de Gier:
I am interested to investigate endophytes in roots across the 196 F2 genotypes in Brassica oleracea. This project presents the first screening of whether or not root endophytes correlate with life history traits.
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- Dória LC, Podadera DS, del Arco M, Chauvin T, Smets E, Delzon S, Lens F. 2018. Insular woody daisies (Argyranthemum, Asteraceae) are more resistant to drought-induced hydraulic failure than their herbaceous relatives. Functional Ecology 32: 1467-1478
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- Melzer S, Lens F, Gennen J, Vanneste S, Rhode A, Beeckman T. 2008. Flowering-time genes modulate meristem determinacy and growth form in Arabidopsis. Nature Genetics 40: 1489-1492