Characterization and functional analysis of Floweringlocus T (FT) and Terminal Flower 1 (TFL1) orthologs in coffeaarabica l.: moving forward into understanding coffee flowering

Abstract

Human food is directly or indirectly dependent of vegetables, grain and fruits, therefore, the understanding of vegetative and reproductive development in plants is mandatory. Many studies about this topic are focused on annual species. However, understanding of flowering is poorly understood in perennial species such as those with biannual cycle, such as, coffee plants (Coffea arabica L.). In general, the floral induction processes are largely conserved between Angiosperms and coordinated by six main molecular pathways: age, vernalization, gibberellin, temperature, photoperiod and the autonomous one. These pathways interact with each other and, also respond to environmental signals specifying the exact transition time from vegetative to reproductive meristems. Regarding these pathways, two genes are considered main regulators acting antagonistically, the FLOWERING LOCUS T (FT) as floral inducer, and the TERMINAL FLOWER LOCUS 1 (TFL1) as a floral repressor. The C. arabica phenological cycle is strongly affected by climatic aspects being observed as asynchrony of its floral meristems development, which result in many flowering events and fruit inequality. This is an undesired effect since it causes a lower beverage quality in no selective harvest. In addition, coffee production has great socioeconomic importance to many countries, including Brazil, justifying the interest in understanding its flowering control. This thesis addressed the study of coffee flowering regulation by the functional characterization of FT and TFL1 genes from Coffea arabica. We compared both phenotypic among different cultivars during the reproductive cycle, including Coffea canephora, to find contrasting aspects in flowering regulation. As an outline, this thesis is divided in five sections: Section #1 is a General introduction; Section #2, Manuscript #1, is a minireview focused on FT and TFL1 in perennial species with polycarpic behavior; Section #3, Manuscript #2, describes the functional characterization of FT orthologs in Coffea arabica (CaFT) as well as other genes associated with flowering regulation, and also a new hypothesis for flower induction time that may explain the many flowering events occurring in the coffee plant. Section #4, Manuscript #3, focuses on the functional characterization of Coffea arabica TFL1 ortholog (CaTFL1), describing its possible post transcriptional regulation, which might be associated with the asynchronous coffee flowering trait. And the section #5 is a general conclusion about the findings of the experimental work in this thesis. Thus, the results obtained here contribute to the understanding of the perennial species flowering process, as well as, coffee flowering time and, therefore, opens new possibilities to controlling its flowering.