Lehrstuhl für Pflanzenzüchtung

Flowering time regulation in Beta species

Zwei Studenten und eine Tasse Kaffee

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Background

The transition from vegetative to generative growth in the lifetime of a flowering plant is triggered by a number of genes together with endogenous stimuli as well as environmental cues, such as temperature or day length changes. To ensure optimal reproductive success, flowering plants have developed different life cycles. Sugar beet (Beta vulgaris) is a biennial root crop that grows vegetatively in the first year and starts shoot elongation (bolting) and flowering after exposure to cold temperatures (vernalization) after winter. The BOLTING TIME CONTROL 1 (BTC1) gene at the bolting locus B was discovered to control annuality (bolting without vernalization) through regulation of the two beet FT homologs BvFT1 and BvFT2.

Besides BTC1, a second bolting time locus B2 has been identified among the offspring of an ethylmethanesulfonate (EMS) mutagenized annual beet accession carrying the dominant BTC1 allele.

Objectives

We aim to understand life cycle adaption in the context of the genetic network that regulates floral transition in sugar beet, with the long-term objective of providing a tool kit for targeted modification of bolting and flowering time. Applications in plant breeding include suppression of vernalization responsiveness to enable winter cultivation and marker-assisted selection for synchronization of flowering time for hybrid seed production, as well as understanding and expanding the evolutionary relationship of flowering time pathways between Beta and other species.

Results

We have identified a transcription factor at the second bolting locus B2 on chromosome 9 by map-based cloning. The gene was termed BvBBX19 according to its closest homolog from Arabidopsis thaliana. The encoded protein has two conserved domains with homology to zinc finger B-boxes. We could show that BvBBX19 is diurnally regulated and, like BTC1, acts  upstream of BvFT1 and BvFT2. EMS-induced mutations within the second B-box caused upregulation of BvFT1 and complete downregulation of BvFT2, demonstrating that these mutations have a strong impact on the function of the BTC1 protein turning an annual plant homozygous for the annual BTC1 allele into a biennial one which can only flower after vernalization. The results indicate that BvBBX19 acts together with BTC1 to induce bolting and flowering in beet.

In collaboration with our partners from the DFG priority program (www.flowercrop.uni-kiel.de) we are investigating protein interactions between BvBBX19 and BTC1. In order to functionally characterize the two genes in beet, we developed F2 and F3 populations that segregate for BTC1 and BvBBX19. The F2 population was grown under controlled conditions in a climate chamber and phenotyped for bolting before and after cold treatment. In order to verify the observations made in this experiment, the F3 population was planted in a gauzehouse under semi-natural conditions in autumn and phenotyped for bolting time after winter. Currently, we measure the effect of different BTC1 and BvBBX19 allele combinations on the expression of the floral activator BvFT2. Additionally, we have transformed Arabidopsis wildtype and mutant plants with BTC1 and BvBBX19 that will be phenotyped for flowering time in future. 

Besides the functional characterization of the two key flowering time genes BTC1 and BvBBX19, we phenotyped plants from a diverse Beta panel and genotyped them for BvBBX19, BTC1, BvFT1 and BvFT2 in order to elucidate the correlation between the geographical origin of an accession and its bolting behavior. We found that accessions from Northern latitudes flower significantly later and some plants did not flower at all, indicating a strong impact of latitude of origin on life cycle. In general, sea beets showed a higher heterogeneity in terms of haplotypes than most cultivated sugar beets. Furthermore, we observed a high conservation in domains such as CCT, REC, BBX and PEBC, underlining their relevance for life cycle adaptation.

Project team

Dr. Nadine Dally
Dr. Nadine Höft
Dr. Ronja Wonneberger
Monika Bruisch
Kerstin Wulbrandt
Prof. Dr. Christian Jung

Scientific Partners

Dr. Daniela Holtgräwe (CeBiTec, University of Bielefeld, Germany)
Prof. Dr. Bernd Weisshaar (Chair of Genome Research, University of Bielefeld, Germany)
Prof. Dr. George Coupland, Max Planck Institute for Plant Breeding Research, Cologne, Germany
Prof. Dr. Alfred Batschauer, Molecular Plant Physiology and Photobiology, Philipps-University Marburg, Marburg, Germany

Publications

Höft N., Dally N., Jung C. (2018). Sequence variation in the bolting time regulator BTC1 changes the life cycle regime in sugar beet. Plant Breeding 2018;00:1–11.

Höft, N., Dally, N. Hasler, M., Jung, C. (2018) Haplotype variation of flowering time genes of sugar beet and its wild relatives and the impact on life cycle regimes. Frontiers in Plant Science, 8:2211.

Blümel, M., N. Dally, Jung, C. (2015) Flowering time regulation in crops-what did we learn from Arabidopsis? Current Opinion in Biotechnology 32C: 121-129.

Dally, N. (2015) Identification of the transcription factor BvBBX19 and its role in flowering time control in beet. 17. Kurt von Rümker-Vorträge 85: 19-26.

Pfeiffer N, Tränkner C, Lemnian I, Grosse I, Müller AE, Jung C, Kopisch-Obuch FJ (2014). „Genetic analysis of bolting after winter in sugar beet (Beta vulgaris L.).” Theoretical Applied Genetics 127:2479-2489, doi:10.1007/s00122-014-2392-x.

Vogt S, Weyens G, Lefèbvre M, Bork B, Schechert A, Müller AE (2014). “The FLC-like gene BvFL1 is not a major regulator of vernalization response in bennial beets.” Frontiers in Plant Science (5), doi: 10.3389/fpls.2014.00146.

Dally, N., K. Xiao, et al. (2014). "The B2 flowering time locus of beet encodes a zinc finger transcription factor." Proc Natl Acad Sci U S A 111(28): 10365-10370.

Melzer S, Müller AE, Jung C (2014). Genetics and genomics of flowering time regulation in sugar beet In: Genomics of Plant Genetic Resources, Vol. 2., Crop productivity, food security and nutritional quality. (Eds: R. Tuberosa, A. Graner, E. Frison). Springer 2014. ISBN: 978-94-007-7575-6, S.3-27.

Frerichmann SLM, Kirchhoff M, Müller AE, Scheidig AJ, Jung C, Kopisch-Obuch FJ (2013). „EcoTILLING in Beta vulgaris reveals polymorphisms in the FLC-like gene BvFL1 that are associated with annuality and winter hardiness.” BMC Plant Biology 13:52, doi:10.1186/1471-2229-13-52.

Pin, P. A., Zhang, W., Vogt, S. H., Dally, N., Büttner, B., Schulze-Buxloh, G., Jelly, N. S., Chia, T. Y. P., Mutasa-Göttgens, E. S., Dohm, J. C., Himmelbauer, H., Weisshaar, B., Kraus, J., Gielen, J. J. L., Lommel, M., Weyens, G., Wahl, B., Schechert, A., Nilsson, O., Jung, C., Kraft, T., Müller, A. E. (2012) The role of a pseudo-response regulator gene in lifecycle adaptation and domestication of beet. Current Biology 22:1095-1101.

Kirchhoff M, Svirshchevskaya A, Hoffmann C, Schechert A, Jung C, Kopisch-Obuch FJ (2012)” High degree of genetic variation of winter hardiness  in a panel of Beta vulgaris L.” Crop Science 52:179-188.

Büttner, B., Abou-Elwafa, S. F., Zhang, W., Jung, C. and Müller, A (2010) A survey of EMS-induced biennial Beta vulgaris mutants reveals a novel bolting locus which is unlinked to the bolting gene B. Theoretical and Applied Genetics 121:1117-1131.

Abou-Elwafa S. F., Büttner B., Chia T., Schulze-Buxloh G. Hohmann U., Mutasa-Göttgens E., Jung C., Müller A. E. (2011) “Conservation and divergence of the autonomous pathway of flowering time regulation in Beta vulgaris.” Journal of Experimental Botany 62:3359-3374.

Posters and Oral Presentations

Dally, N., Jung, C. (2018) Unravelling a genetic network for bolting time regulation in Beta species to breed winter sugar beet, Flower Crop-SPP1530 Final Symposium, 14.-16.03.2018, Kiel, Oral Presentation.

Jung, C. (2018) Genetic analysis of flowering time regulation in sugar beet and related species offering new perspectives for breeding, PAG XXVI, Plant Reproductive Genomics Workshop, 14.01.2018, San Diego, USA, Oral Presentation.

Jung, C. (2017) Flowering time regulation in a vegetative crop and application in breeding, Crop Genomics: Present & Future symposium, ICRISAT, Hyderabad, India, 07.12.2017, Oral Presentation.

Dally N., Eckel M., Batschauer A., Jung C. (2016) Characterization of Two Key Regulators Controlling Bolting Time in Beta Species Reveals a Novel Mechanism for Floral Transition in Beet, Euro Plant Biology 2016 (EPSO), Prague, 26-30.06.2016, Oral Presentation.

Höft N., Dally N., Jung C. (2016) The Impact of Geographical Origin of Beta Species on its Different Life Cycle Regimes, Flower Crop-SPP1530 Workshop on circadian rhythms, Berlin 20.-22.01.2016, Oral Presentation.

Dally N.,  Eckel M., Höft N., Batschauer A., Jung C. (2016) Functional analysis of two key regulators for bolting time in Beta species to breed winter sugar beets“, Flower Crop-SPP1530 Workshop on circadian rhythms, Berlin 20.-22.01.2016, Poster Presentation.

Höft N., Dally N., Jung C. (2015) Unravelling the Origin of the Crop Sugar Beet: Towards Understanding the Evolution of different Life Cycle Regimes in Beta Species,  IPMB 2015: 11th Congress of International Plant Molecular Biology (IPMB), Iguazú Falls, Brazil, 25. – 30.10.2015, Poster Presentation.

Höft, N., Dally, N., Jung C. (2014) Life cycle adaption in beet - identification of a new bolting time gene.  GPZ 2014: Genetic Variation in Plant Breeding, University Kiel 23.-25.09.2014. Poster Presentation.

Höft, N., Dally, N., Jung C. (2014) Functional characterization of a new bolting time gene from sugar beet. II. International Symposium: Genetic Variation of Flowering Time Genes and Applications for Crop Improvement, University Bielefeld 24.-26.03.2014. Poster Presentation.

Höft, N., Tränkner C., Jung C., Melzer S. (2012) Control of flowering in sugar beet and Arabidopsis through activation of flowering time repressors by FLP-FRT recombination. "Breeding crops for sustainable agricultural production" Symposium of GPZ e.V., Gießen 28.2.-1.3.2012. Poster Presentation.

Financial Support

Funding has been provided by the Deutsche Forschungsgemeinschaft under grant No.  DFG JU 205/14-1 and the International Max Planck Research School for Evolutionary Biology, Plön/Kiel. The project is part of the DFG Priority Program 1530: Flowering Time Control – from Natural Variation to Crop Improvementl.

 

Updated: 27-July-18           Responsible for this webpage: Dr. Ronja Wonneberger