Genomic dissection of floral transition in Brassica napus towards crop improvement by life cycle adaptation and hybrid yield increase
Final Report Abstract
Rapeseed (Brassica napus L) , one of the most important sources of vegetable oil and protein-rich meals worldwide, is adapted to different environments by modification in requirements for day length and vernalization. A broad variation exists from very early-flowering spring-type to late-flowering winter cultivars, which only flower after exposure to an extended cold period. Identification of genes that promote or inhibit flowering may hold an important key for sustainable agriculture under distinct environmental conditions. In this study, we aimed to identify flowering time regulators from B. napus and characterize their possible pleiotropic effects on yield and yield components. We combined three different approaches (TILLING, transcriptome analysis and genetic mapping and association analysis) to get a deeper insight into floral regulation in rapeseed. We have identified more than 300 EMS-mutated alleles in paralogs of four major flowering time regulators, FRIGIDA, FLOWERING LOCUS-T (FT), TERMINAL FLOWER-1 (TFL1) and APETALA 1 (AP1) via TILLING in the winter rapeseed inbred line Express 617. Mutations in single FT gene copies showed altered flowering time phenotypes, while mutations within the BnTFL1-2 paralog had no large effects on flowering time, but on yield components. F 1 hybrids between BnTFL1-2 mutants and nonmutated Express 617 lines showed superior seed numbers and seed yield compared to Express617, suggesting that heterozygous mutations in one TFL1 paralog may impact heterosis in rapeseed. We demonstrate that even mutations in only one BnFT and BnTFL1 paralog have effects on flowering time and yield despite the redundancy of the rapeseed genome. Moreover, our results suggest pleiotropic effects of BnTFL1 paralogs beyond the regulation of flowering time. The EMS lines constitute a new source of genetic variation for rapeseed breeding. To gain a deeper insight into genetic factors controlling floral transition in B. napus, RNA-seq has been performed in the semi-winter doubled haploid line Ningyou7 at different developmental stages and under two temperature regimes. The expression profiles of more than 66,000 gene models were analyzed and a bioinformatics pipeline was developed by iterative RNA-seq-quantification and RT-qPCR validation cycles. Further analysis of RNA-seq data through comparison of the expression patterns between different treatments and developmental stages revealed 3,183 putative candidate genes which might play a role in flowering time control in rapeseed, out of which 47 genes were orthologs of known flowering time regulators in Arabidopsis. In the next step, the candidate genes were considered for genetic mapping and association analysis to confirm their role in flowering time regulation in rapeseed. We observed significant association between the paralogs of FLC, VIN3, SOC1, FUL, FRI and UBC and flowering time and/or yield, which highlights these genes as promising candidates, not only as putative flowering time regulators, but also as major determinants of yield and yield components in rapeseed.
Publications
- (2014) Mutations in single FT- and TFL1-paralogs of rapeseed (Brassica napus L.) and their impact on flowering time and yield components. Frontiers in plant science 5
Guo Y, Harloff H-J, Jung C, Molina C
(See online at https://doi.org/10.3389/fpls.2014.00282) - 2014. Identification of flowering time genes in rapeseed (Brassica napus L.) through TILLING and RNA-seq analysis. Genetic Variation of Flowering Time Genes and Applications for Crop Improvement, March 2014, Bielefeld, Germany
Guo Y., N. Emrani, N. Jedrusik, C. Weinholdt, I. Lemnian, C. Molina, I. Grosse and C. Jung
- 2015. Induced sequence variations within life cycle genes of rapeseed and their impact on flowering time and hybrid yield. 14th International Rapeseed Congress, July 2015, Saskatoon, Canada
Jung C., Y. Guo, H. Harloff and C. Molina
- 2015. Molecular dissection of flowering time regulation in Brassica napus and application for hybrid breeding. 4th Annual Consortium Meeting, April 2015, Weihenstephan, Germany
Emrani, N., S. Shah, C. Weinholdt, C. Molina, Y. Guo, N. Jedrusik, I. Große and C. Jung
- 2015. Mutations in FT-, FTL1-, and FRI paralogs of rapeseed (Brassica napus L.) and their effect on flowering time and heterosis. Diss., Kiel University
Guo Y.
- 2016. Identification and characterization of flowering time genes in oilseed rape through TILLING and transcriptome analysis. Workshop on circadian rhythms, flowering time genes and crop plant adaptation, January 2016, Berlin, Germany
Shah, S., N. Emrani, C. Weinholdt, C. Molina, Y. Guo, N. Jedrusik, I. Große and C. Jung
