Abstract
Changes in light quality indicative of competition for this essential resource influence plant growth and developmental transitions; however, little is known about neighbor proximity-induced acceleration of reproduction. Phytochrome B (phyB) senses light cues from plant competitors, ultimately leading to the expression of the floral inducers FLOWERING LOCUS T (FT) and TWIN SISTER of FT (TSF). Here we show that PHYTOCHROME INTERACTING FACTORs 4, 5 and 7 (PIF4, PIF5 and PIF7) mediate neighbor proximity-induced flowering, with PIF7 playing a prominent role. These transcriptional regulators act directly downstream of phyB to promote expression of FT and TSF. Neighbor proximity enhances PIF accumulation towards the end of the day, coinciding with enhanced floral inducer expression. We present evidence supporting direct PIF-regulated TSF expression. The relevance of our findings is illustrated by the prior identification of FT, TSF and PIF4 as loci underlying flowering time regulation in natural conditions.
Highlights
Changes in light quality indicative of competition for this essential resource influence plant growth and developmental transitions; little is known about neighbor proximityinduced acceleration of reproduction
Because low R/FR further accelerates flowering in Phytochrome B (phyB) mutant due to the activity of other phys[27,28] (Supplementary Fig. 5a–c), we scored phyB pif[4] pif[5] pif[7] flowering in low R/FR
We conclude that PIF4, PIF5, and PIF7 act genetically downstream of phyB, and possibly other phys, to control low R/FR-induced flowering
Summary
Changes in light quality indicative of competition for this essential resource influence plant growth and developmental transitions; little is known about neighbor proximityinduced acceleration of reproduction. Phytochrome B (phyB) senses light cues from plant competitors, leading to the expression of the floral inducers FLOWERING LOCUS T (FT) and TWIN SISTER of FT (TSF). We show that PHYTOCHROME INTERACTING FACTORs 4, 5 and 7 (PIF4, PIF5 and PIF7) mediate neighbor proximity-induced flowering, with PIF7 playing a prominent role These transcriptional regulators act directly downstream of phyB to promote expression of FT and TSF. At the SAM the FAC induces flowering by activating the expression of flowering time genes, such as the MADS-box SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) and APETALA1 (AP1)[16,17] Despite their importance for shade-induced flowering, the mechanism linking low R/FR ratio perception by phys to enhanced FT and TSF expression in the vasculature remains poorly understood. We show that a subset of PIF transcription factors function genetically downstream of phys to regulate flowering time through FT and TSF expression in response to low R/FR
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