Photoperiod and temperature are major environmental signals affecting flowering in plants. Although molecular pathways mediating these signals have been well characterized in the annual model plantArabidopsis, much less information is known in perennials. Many perennials including the woodland strawberry (Fragaria vescaL.) are induced to flower in response to decreasing photoperiod and temperature in autumn and they flower following spring. We showed earlier that, in contrast withArabidopsis, the photoperiodic induction of flowering in strawberry occurs in short days (SD) when the decrease inFvFT1(FLOWERING LOCUS T) andFvSOC1(SUPPRESSOR OF THE OVEREXPRESSION OF CONSTANS1) expression leads to lower mRNA levels of the floral repressor, FvTFL1 (TERMINAL FLOWER1). By using transgenic lines and gene expression analyses, we show evidence that the temperature-mediated changes in theFvTFL1mRNA expression set critical temperature limits for the photoperiodic flowering in strawberry. At temperatures below 13°C, low expression level ofFvTFL1in both SD and long days (LD) allows flower induction to occur independently of the photoperiod. Rising temperature gradually increasesFvTFL1mRNA levels under LD, and at temperatures above 13°C, SD is required for the flower induction that depends on the deactivation ofFvSOC1andFvTFL1. However, an unknown transcriptional activator, which functions independently of FvSOC1, enhances the expression ofFvTFL1at 23°C preventing photoperiodic flowering. We suggest that the observed effect of the photoperiod × temperature interaction onFvTFL1mRNA expression may allow strawberry to induce flowers in correct time in different climates.Significance Statement
Many perennial plants are induced to flower in response to decreasing photoperiod and temperature in autumn. We show here that, in the perennial woodland strawberry, temperature strongly affects the mRNA expression of the major floral repressor TERMINAL FLOWER1 setting critical temperature limits for the photoperiodic flower induction.