Flowering: a time for integration

Flowering time is under the control of multiple environmental cues such as photoperiod and exposure to cold temperatures (vernalization). A few regulators named integrators of flowering time signals (LEAFY, SOC1/AGL20 and FT) integrate inputs from the different flowering cascades and convey the resulting outcome to floral meristem identity genes at the shoot apex. Here we review the current knowledge about the expression of integrators, their mode of action, their potential target genes and the nature of their mutual interactions. We emphasize the questions that have been generated by recent progress in this field and that remain to be addressed.