AbstractsBiology & Animal Science

The transition from vegetative to reproductive development is a key developmental step in the life cycle of a flowering plant. Floral transition is a complex biological process, which is controlled by multiple flowering genes that respond to environmental cues and endogenous signals. Arabidopsis thaliana is an excellent model system for the Brassicaceae plant family. This study deals with three major flowering time regulators from oilseed rape (Brassica napus), an allopolyploid species which originated from natural hybridization between B. rapa and B. oleracea. The aim of this study was to identify and characterize B. napus orthologs of the A. thaliana flowering time genes FT, TFL1 and FRI. First, I searched the NCBI and Brassica databases to identify paralogs of FT, TFL1 and FRI in rapeseed. Then, I designed paralog specific primers to search for mutations in three genes (BnC6FTa/b, BnTFL1-2, BnaA.FRI.a) using a TILLING mutant population of the European winter type oilseed rape Express 617. Altogether, 117 mutants were identified. Four non-sense and twenty missense mutant lines (M3) were further characterized. Homozygous M3 lines were produced by selfing M2 plants. They were grown in the greenhouse and their flowering time as well as yield components were analysed. BnFT paralogs contributed differently to flowering time regulation. Despite the redundancy of mutations in a single gene, either nonsense or missense mutations in the BnC6FTb gene resulted in a marked flowering delay, whereas all five BnC6FTa mutant lines started flowering as the non-mutated parent. Mutations within the BnTFL1-2 paralog had no large effects on flowering time but on yield components. F1 hybrids between BnTFL1-2 mutants and non-mutated parents had increased seed numbers per pod and total seeds per plant suggesting that heterozygous mutations in a TFL1 paralog may impact heterosis in rapeseed. Mutations within the BnaA.FRI.a paralog showed pleiotropic effects beyond the regulation of flowering time. Moreover, the expression of the mutant alleles and their downstream genes were analysed. To my surprise, a splice site mutation of BnC6FTb, and even a missense mutation of BnaA.FRI.a had an effect on the transcriptional activities of two downstream flowering time regulators, BnSOC1 and BnAP1 despite the presence of multiple paralogs. Moreover, the expression of three BnFLC paralogs was altered due to a missense mutation in a single BnFRI paralog. This demonstrates multiple interactions between BnFRI and BnFLC paralogs in an allopolyploid species. Der Übergang von der vegetativen zur reproduktiven Entwicklung ist ein wichtiger Entwicklungsschritt im Lebenszyklus einer Blütenpflanze. Die Blühinduktion ist ein komplexer biologischer Vorgang, der durch mehrere Blühgene gesteuert wird, die auf Umweltreize und endogene Signale reagieren. Arabidopsis thaliana ist ein ausgezeichnetes Modellsystem für die Pflanzenfamilie der Brassicaceae. Diese Studie befasst sich mit drei wesentlichen Blühregulatoren aus Raps (Brassica…