Unraveling a mechanism for floral transition control in annual, biennial, and perennial Beta species
Final Report Abstract
Sugar beet (Beta vulgaris ssp. vulgaris) is the only sucrose storing crop cultivated in temperate regions worldwide. Conventionally, it is sown in spring and harvested before winter in the vegetative stage. Floral transition, which results in bolting, is undesired in sugar beet production areas because it drastically reduces the beet and sugar yield. On the other hand, bolting is required to produce seeds. The taxon Beta vulgaris includes mono- and polycarpic plants and shows a considerable variation for bolting time. To elucidate genetic mechanisms of bolting control, the following studies using Beta accessions or crossing populations with different phenological development were performed: i) a RNAseq study using shoot apices of the monocarpic-annual sugar beet accession 001684, ii) QTL analyses using populations derived from crosses of 001684 with polycarpic wild beets, and iii) a bulked segregant NGS analysis using a F2 sugar beet population that segregates for bolting and nonbolting after cold-treatment. i) In January-sown plants of 001684, the floral transition occurred at the 6 to 8-leaf stage. By RNAseq, a decrease in transcription until the 6 to 8-leaf stage followed by a low or even no expression during the reproductive growth phase as expected for floral repressor genes was detectable for 488 genes including the B. vulgaris floral repressor gene BvFT1 and genes with homology to SMZ, RGA1, FRL1 and FRL2 of Arabidopsis. In contrast, a transcription increase starting from the 6 to 8-leaf stage or a gradual increase starting from the 2-leaf stage as expected for floral promoter genes were detected for 1418 genes including Beta genes with homology to SOC1 and FUL/AP1 of Arabidopsis. ii) Three F2 populations from crosses of mono- and polycarpic beets were developed that segregated for vernalization requirement, bolting time, and the mono-/polycarpic traits death after reproduction, reversion to vegetative growth after reproduction, and repeated bolting and flowering. No QTL was detected for the mono- and polycarpic traits. However, two major QTL were detected for seasonal bolting time. One QTL is co-localized with the floral promoter gene BvFT2 on chromosome 4, whereas the other QTL on chromosome 9 is co-localized with a previously published QTL for post-winter bolting resistance (Pfeiffer et al. 2014). The late-bolting alleles of both QTL were independently derived from the polycarpic accessions and both loci show an additive interaction for bolting delay. Unexpectedly, the F2 population 120310 also segregated for plants with normal or dwarf growth and a single QTL for dwarf growth was mapped to the North of chromosome 9. iii) By bulked segregant NGS analysis of post-winter bolting and non-bolting F2 plants, a single continuous homozygous region of about 916kb was identified at the South of chromosome 9 that overlaps with a previously published QTL for post-winter bolting resistance (Pfeiffer et al. 2014). By marker analyses, the BR1 locus could be narrowed down to a sub-region that contains only 12 genes. Out of these genes, Bv9_227370_yfgr, a homologue of the Arabidopsis gene CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR 73-I (CPSF73-I), was determined by sequence and transcription analyses as the most promising candidate for post-winter bolting resistance which is assumed to be caused by a 2bp deletion within the bolting resistance allele of this gene.
Publications
- 2012. Strategy for mapping bolting repressor genes of sugar beet by next generation sequencing. 1st Young Investigator Meeting PP 1530, Halle/Saale 18.-20.6.2012
Tränkner, C., N. Pfeiffer, M. Schilhabel, F. Kopisch-Obuch, M. Kirchhoff, I. Lemnian, I. Große
- 2012. Towards mapping of bolting failure genes of sugar beet (Beta vulgaris ssp. vulgaris) by next generation sequencing. GPZ Genome Research Working Group 10. Conference – Plant Stress and Genomics, Halle 18.-20.09.2012
Tränkner, C. I. Lemnian, N. Pfeiffer, C. Weinholdt, M. Kirchhoff, F. Kopisch-Obuch, M. Schilhabel, I. Große
- 2014. Analysis of whole-genome sequencing data for elucidating foral transition and discovery of non-bolting genes in Beta vulgaris. PP1530 Symposium: Genetic Variation of Flowering Time Genes and Applications for Crop Improvement, Bielefeld 24-26 March 2014
Lemnian, I., C. Tränkner, N. Pfeiffer, N. Emrani, C. Weinholdt, F. Kopisch-Obuch, M. Schilhabel, C. Jung, I. Grosse
- 2014. Genetic analysis of bolting after winter in sugar beet (Beta vulgaris L.). Theoretical and Applied Genetics
Pfeiffer, N., C. Tränkner, I. Lemnian, I. Grosse, A.E. Müller, C. Jung, F.J. Kopisch-Obuch
(See online at https://doi.org/10.1007/s00122-014-2392-x) - 2014. Identification of bolting failure candidate genes in sugar beet (Beta vulgaris) by Next Generation Sequencing. Genetic Variation of Flowering Time Genes and Applications for Crop Improvement, 24-26 March 2014, Bielefeld
Emrani, N., I. Lemnian, C. Weinholdt, I. Große, N. Pfeiffer, F. Kopisch-Obuch, C. Jung, M. Schilhabel, C. Tränkner
- 2014. Identification of bolting failure candidate genes in sugar beet (Beta vulgaris) by Next Generation Sequencing. PP1530 Symposium: Genetic Variation of Flowering Time Genes and Applications for Crop Improvement, Bielefeld 24-26 March 2014
Tränkner, C., I. Lemnian, C. Weinholdt, N. Pfeiffer, F. Kopisch-Obuch, C. Jung, N. Emrani, M. Schilhabel, I. Grosse
- 2014. Identification of post winter bolting resistance genes of sugar beet (Beta vulgaris) by bulked segregant Next Generation Sequencing. GPZ 2014: Genetic Variation in Plant Breeding, Kiel, Sept 23-25, 2014
Tränkner, C., I. Lemnian, N. Pfeiffer, N. Emrani, S. Vogt, M. Schilhabel, C. Weinholdt, A. Müller, C. Jung, F. Kopisch-Obuch, I. Große
- Analysis of whole-genome sequencing data for elucidating floral transition and discovery of bolting resistance genes in Beta vulgaris. Central German Meeting on Bioinformatics, Halle, July 2015
Lemnian, I., C. Tränkner, C. Weinholdt, N. Emrani, N. Pfeiffer, F. Kopisch-Obuch, M. Schilhabel, C. Jung, I. Grosse
