(800-97) Unraveling the Role of BnFT Genes in Flowering Time Regulation in Brassica napus: Insights from Cross-Species Complementation and Photoperiod-Response Expression Analysis
Body of Abstract: Brassica napus, a crop that greatly contributes to global agricultural economies, originated around 7.5 thousand years ago through interspecific hybridization between Brassica rapa and Brassica oleracea, resulting in a complex genome with A and C sub-genomes.
Flowering time, a crucial phenological trait, directly affects the yield potential and economic sustainability of B. napus. In Arabidopsis thaliana, the FLOWERING LOCUS T (FT) gene plays a pivotal role in flowering regulation, encoding "florigen," a mobile signal synthesized in leaves and moves to the apical meristem to trigger the transition from vegetative to reproductive growth. Despite the well-characterized functions and regulatory mechanisms of the FT gene in Arabidopsis, research on the FT gene in B. napus, a species belonging to the same family as Arabidopsis, is relatively limited.
To address this gap, we identified and characterized six BnFT candidates in B. napus. Cross-species complementation experiments reveal that all six BnFT candidates possess florigen function, with two BnFT candidates that are not located in At.FT syntenic position showing reduced florigen capacity. Furthermore, four syntenic BnFT genes contain conserved Blocks A, C and E on their flanking sequence. These Blocks are known to be involved in transcriptional regulation of At.FT. Photoperiod-response expression analysis of six BnFT candidates demonstrate that four syntenic copies share a common expression trend, an upward parabola with the lowest expression at ZT8, whereas the two non-syntenic copies show an irregular expression and a general lower expression level. Additionally, the overall expression level of four syntenic BnFT genes decrease with increasing distance between Block A and Block C. Currently, we are further validating the impact of distance between regulatory regions using a DUAL-Luciferase reporter system.
In sum, our findings provide insights into how transcription regulation and changes in protein sequence have contributed to the regulatory mechanisms of flowering time in B. napus.