Modeling Floral Induction in the Narrow-Leafed Lupin <i>Lupinus angustifolius</i> Under Different Environmental Conditions

Flowering is initiated in response to environmental cues, with the photoperiod and ambient temperature being the main ones. The regulatory pathways underlying floral transition are well studied in <i>Arabidopsis thaliana</i> but remain largely unknown in legumes. Here, we first applied an in silico approach to infer the regulatory inputs of four <i>FT</i>-like genes of the narrow-leafed lupin <i>Lupinus angustifolius</i>. We studied the roles of <i>FTc1</i>, <i>FTc2</i>, <i>FTa1</i>, and <i>FTa2</i> in the activation of meristem identity gene <i>AGL8</i> in response to 8 h and 16 h photoperiods, vernalization, and the circadian rhythm. We developed a set of regression models of <i>AGL8</i> regulation by the <i>FT</i>-like genes and fitted these models to the recently published gene expression data. The importance of the input from each <i>FT</i>-like gene or their combinations was estimated by comparing the performance of models with one or few <i>FT</i>-like genes turned off, thereby simulating loss-of-function mutations that were yet unavailable in <i>L. angustifolius</i>. Our results suggested that in the early flowering <i>Ku</i> line and intermediate <i>Pal</i> line, the <i>FTc1</i> gene played a major role in floral transition; however, it acted through different mechanisms under short and long days. Turning off the regulatory input of <i>FTc1</i> resulted in substantial changes in <i>AGL8</i> expression associated with vernalization sensitivity and the circadian rhythm. In the wild <i>ku</i> line, we found that both <i>FTc1</i> and <i>FTa1</i> genes had an essential role under long days, which was associated with the vernalization response. These results could be applied both for setting up new experiments and for data analysis using the proposed modeling approach.