An explanatory model of temperature influence on flowering through whole-plant accumulation of FLOWERING LOCUS T in Arabidopsis thaliana

Abstract

We assessed mechanistic temperature influence on flowering by incorporating temperature-responsive flowering mechanisms across developmental age into an existing model. Temperature influences the leaf production rate as well as expression of <i>FLOWERING LOCUS T</i> (<i>FT</i>), a photoperiodic flowering regulator that is expressed in leaves. The <i>Arabidopsis</i> Framework Model incorporated temperature influence on leaf growth but ignored the consequences of leaf growth on and direct temperature influence of <i>FT</i> expression. We measured <i>FT</i> production in differently aged leaves and modified the model, adding mechanistic temperature influence on <i>FT</i> transcription, and causing whole-plant <i>FT</i> to accumulate with leaf growth. Our simulations suggest that in long days, the developmental stage (leaf number) at which the reproductive transition occurs is influenced by day length and temperature through <i>FT</i>, while temperature influences the rate of leaf production and the time (in days) the transition occurs. Further, we demonstrate that <i>FT</i> is mainly produced in the first 10 leaves in the Columbia (Col-0) accession, and that <i>FT</i> accumulation alone cannot explain flowering in conditions in which flowering is delayed. Our simulations supported our hypotheses that: (i) temperature regulation of <i>FT</i>, accumulated with leaf growth, is a component of thermal time, and (ii) incorporating mechanistic temperature regulation of <i>FT</i> can improve model predictions when temperatures change over time.