The contrasting flowering-time among coffee genotypes is associated with ectopic and differential expressions of genes related to environment, floral development, and hormonal regulation

The molecular pathways underlying floral activation and development are well described in model species, but exhibit significant diversity in plants that is poorly understood in crops with complex cycles, such as Coffea arabica L. The reproductive development of coffee plants is biannual, and the flowering time is crucial for the coffee productivity and cup quality. In this study, we explored the plasticity of floral development and flowering-time of contrasting coffee genotypes to understand the associated metabolic and regulatory transcriptional profiles. Firstly, we compared the reproductive development of three coffee genotypes, confirming that Acaua is late flowering, Oeiras is early flowering, and the natural mutant Semperflorens (Sf) exhibits continuous flowering throughout the year. Analysis of sugar and ethylene content revealed quantitative differences between genotypes in both leaves and floral buds. To associate these phenotypic differences with the regulatory developmental pathways, we performed RNA-seq analysis comparing the shoot apical meristems, floral buds and leaves of different genotypes. Our analysis identified 12.478 differentially expressed genes, which showed enriched terms mainly related to hormonal regulation, external stimulus and floral development. Notably, some major players of reproductive development, as homologs of FLOWERING LOCUS T and MADS-box genes, showed contrasting expression patterns, generally being ectopically upregulated in the Sf mutant. These findings were associated with the phenotypic differences among coffee genotypes. In conclusion, the present study improves the understanding of the divergence of floral development in coffee, providing valuable insights for directing breeding programs and future studies aiming at controlling floral development and enhancing crop production.