Functional characterization of the FT/TFL1 gene family in photoperiodic flowering in Arabidopsis and soybean

The flowering transition represents one of the most important developmental milestones in the plant life cycle. Several interconnected pathways contribute to flowering induction. By coordinating flowering time with environmental input, these pathways help to optimize plant adaptation and reproductive success. The photoperiodic flowering pathway relies on day length in order to ensure the coincidence of plant reproductive development with favorable seasonal timing. The projects described here aimed to characterize the functions of the FT/TFL1 gene family in photoperiodic flowering control in Arabidopsis and soybean. Chapter One reviews plant flowering regulation. It opens by discussing the developmental context of flowering and the importance of photoperiodic flowering control to plant reproduction and agriculture. The chapter then details the mechanisms of the photoperiodic flowering pathway in the model species Arabidopsis thaliana. Next, the photoperiodic flowering pathways in rice, soybean, sugar beet and poplar are covered. The remainder of the chapter surveys five other flowering pathways: the vernalization, ambient temperature, gibberellin and autonomous flowering pathways. Chapter Two reports efforts to characterize the roles of the FT/TFL1 gene family in photoperiodic flowering in Arabidopsis. Using an RNA-sequencing approach, we analyzed mRNA expression data to identify genes potentially regulated by TFL1. Known targets of TFL1 as well as potentially further downstream targets were found. Using a transgenic approach based on two induction systems, we aimed to identify the immediate targets of FT and TFL1. The results of this approach suggest that FT controls downstream genes in an indirect manner. Chapter Three describes research to characterize the functions of soybean FT homologs, particularly in relation to soybean development and evolution. We focused on one such homolog and found that mRNA expression data, gene structure data and functional data suggest that this gene stimulates flowering in wild soybean but is nonfunctional in domesticated soybean