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I am generally interested in questions addressing the phylogeny, evolution, biogeography, and radiation of the Brassicaceae in the light of recent progress in palaeoclimatic and genomic research. Furthermore, I am aiming for understanding the genetic basis of fruit and seed characters and regulation of character changes.

Phylogeny and systematics of the Brassicaceae

DFG MU 1137/7-1 & MU 1137/7-2; project with Andreas Franzke

In addition to the commercial potential of several cruciferous plants (i.e. cabbage), the mustard family (Brassicaceae) is also of great academic interest, as this family contains the most important model organism of modern plant biology, i.e., Arabidopsis thaliana. Notwithstanding this impact, the phylogenetic history of this plant family is only partly understood and a robust real family-wide phylogenetic concept is still missing. The present study deepens our understanding of the Brassicaceae phylogeny with two approaches being new to broad-scale phylogenetic research of the Crucifers: We (i) used a molecular marker from the mitochondrial genome and a (ii) contemporary relaxed molecular dating method to infer key dates in the Brassicaceae evolution. The results obtained from sequencing mitochondrial DNA generally confirms a recent tribal alignment of the Brassicaceae primarily based on chloroplast DNA analyses. Additionally, our data are also compared with a recent family-wide Brassicaceae phylogeny based on nuclear DNA. Combining the results from phylogenetic reconstructions and molecular dating, it is possible for the first time, to present a biogeographical scenario for the broad scale Brassicaceae evolution.

BrassiBase: Tools and biological resources to study characters and traits in the Brassicaceae

DFG priority programme 1529 “Adaptomics”: Evolutionary plant solutions to ecological challenges

Joint project with Marcus Koch (Heidelberg) and Ihsan Al-Shehbaz (Missouri Botanical Garden)

We aim to develop a system of cross-referenced information and resources on Brassicaceae taxonomy, systematics, evolution, chromosome numbers, accurate enumeration of all species, traits and characters and germplasm resources. Biological, molecular and evolutionary knowledge is exponentially increasing in the mustard family (Brassicaceae, Cruciferae). However, because of the complex and overwhelming biological diversity in the family, it is difficult for non-specialists in this plant family to put any research result in a larger evolutionary framework. Many species are remarkable study objects but rarely available. Biological material and resources, either collected directly in the wild or held in germplasm collections, is often taxonomically mis-itentified; and very rarely the material is further characterized and documented. There is also no family-wide and comprehensive survey of character and trait distribution despite the fact that we approached a reliable phylogenetic framework quite recently. In order to close these various gaps and provide the full potential of research focusing on the adaptive characters and character-trait evolution in the Brassicaceae, we will provide a comprehensive documentation of the taxonomy and systematics of the entire family. This will include a database with all the relevant taxonomic, systematic and phylogenetic literature; a comprehensive data collection of characters and traits including all potentially adaptive traits scientists participating in SSP 1529 are interested in; a DNA-based identification tool for genera and species; electronic interactive keys for the identification of genera and species, and a setup of a carefully selected and documented germplasm collection representing the entire family. Basic research will be conducted to provide first and comparative insights into the evolution of characters and traits over the whole family utilizing also the data collected during the project. The results and framework provided herein will be the basis and starting point for other projects focusing in more details on individual characters and traits – inside and outside SSP 1529 “Adaptomics”.

Evolutionary developmental genetics of fruit dehiscence in Brassicaceae

DFG MU 1137/8-1; joint DFG project with Prof. Günter Theissen (Jena, DFG TH417/6-1)

This project is at the interface of phylogenetics, developmental biology, and molecular genetics and it outlines a comparative developmental genetic analysis of fruit evolution in the Brassicaceae, which includes the model species Arabidopsis thaliana. The relative simple genetic mechanism by which the mutant Arabidopsis indehiscent fruits originated from typical wild type dehiscent fruits might easily explain the rapid and independent evolution of indehiscent fruits in different Brassicaceae lineages. Following the rationale of evolutionary developmental biology (‘evo-devo’) phylomimicking mutants with indehiscent fruits of the close relative Arabidopsis have been used to define the candidate genes ALC, FUL, IND, RPL, and SHP1/2 which might be involved in the origin of indehiscent fruits in Lepidium. That way we hope to contribute to a better understanding of the developmental genetic basics of rapid and drastic morphological character changes of during evolution.

Finally, this work will provide insight into how variation in fruit morphology has been achieved at the genetic level. This is an essential goal against the background of increasing importance of reducing seed dispersal in crop plants.

Distinct fruit traits are associated with distinct seed traits, e.g. mucilage production important for dispersal. The molecular mechanisms of Lepidium sativum (bigger seeds) and Arabidopsis thaliana (tiny seeds) seed germination have been studied in comparative work by my collaborator Gerhard Leubner (Freiburg). Seed-tissue-specific transcriptome and proteome analysis, as well as reverse genetics (transgenic seeds) and seed biomechanics are possible with L. sativum. I want to extend this collaboration work to other species of the monophyletic genus Lepidium and later on in other Brassicaceae. Novel seed traits, e.g. dormancy types not found in Arabidopsis, and their evolution, can be studied in Lepidium and other Brassicaceae genera.

Adaptomics of neofunctionalization: analysis of GORDITA-like genes in Brassicaceae

DFG priority programme 1529 “Adaptomics”: Evolutionary plant solutions to ecological challenges

Joint project with Annette Becker (Bremen, project leader) and Günter Theissen (Jena, project leader)

The project investigates how the origin of a single developmental control gene, GORDITA (GOA), by gene duplication and sequence divergence contributed to plant fitness and adaptation in the Brassicaceae. While the ancestral Bsister genes (ABS-type genes) are involved in ovule development, the derived GOA-type genes acquired a new expression domain and function in fruit development. By comprehensive comparative analyses involving GOA-type and ABS-type genes from diverse Brassicales species we will investigate when the lineage that led to extant GOA-type genes originated, and by which molecular mechanisms these genes acquired their unique expression patterns, domain structures, and function during fruit development. To better understand how the ancestors of GOA escaped ‘Ohno’s dilemma’ we will analyze the molecular evolution in the different branches of Bsister genes during the phylogeny of Brassicales employing in silico methods. Using protein-protein interaction studies we will investigate how changes in the protein structure changed the protein interaction network of GOA in comparison of ABS. To assess how the origin of GOA-type genes contributed to the adaptation of Brassicaceae species we will determine proxies of plant fitness under greenhouse conditions using transgenic knock-out plants, and will do preparative work for future determination of plant fitness under natural growth conditions using non-transgenic mutants.

Genome evolution in Cardamine allopolyploids of contrasting phylogenetic age

Joint project with Martin Lysak (Brno, project leader) and Karol Mahold (Prague); funded by the Czech Science Foundation

Polyploidy is playing a crucial role in speciation of spermatophytes. Nevertheless, surprisingly little is known about the chromosome stability in first generations following the polyploid origin and in recent polyploids. For the first time, the combined GISH/CCP technique (Genomic In Situ Hybridization/Comparative Chromosome

Painting) will be applied to analyze inter-genomic chromosomal interactions in Cardamine hybrids and allopolyploids. GISH will identify parental chromosome complements and inter-genomic translocations, whereas CCP will pinpoint inter- and intra-chromosome rearrangements. The chromosome stability will be analyzed in the recent hybrid Cardamine × insueta (2n=24) and its auto-allohexaploid derivative C. schulzii (2n=48) (both c. 100 years old), as compared to an old allotetraploid species C. flexuosa (2n=32). For the three taxa, synthetic lines will be established and the chromosome stability monitored in successive generations. Karyological variation will be related to phylogenetic relationships inferred from the analysis of nuclear and chloroplast markers.