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<jats:title>Abstract</jats:title><jats:p>Floral scent emission of petunia flowers is regulated by light conditions, circadian rhythms, ambient temperature and the phytohormones GA and ethylene, but the mechanisms underlying sensitivity to these factors remain obscure. PHYTOCHROME INTERACTING FACTORs (PIFs) have been well studied as components of the regulatory machinery for numerous physiological processes. Acting redundantly, they serve as transmitters of light, circadian, metabolic, thermal and hormonal signals. Here we identified and characterized the phylogenetics of petunia PIF family members (PhPIFs). PhPIF4/5 was revealed as a positive regulator of floral scent: TRV-based transient suppression of <jats:italic>PhPIF4/5</jats:italic> in petunia petals reduced emission of volatiles, whereas transient overexpression increased scent emission. The mechanism of PhPIF4/5-mediated regulation of volatile production includes activation of the expression of genes encoding biosynthetic enzymes and a key positive regulator of the pathway, EMISSION OF BENZENOIDS II (EOBII). The PIF-binding motif on the <jats:italic>EOBII</jats:italic> promoter (G-box) was shown to be needed for this activation. As PhPIF4/5 homologues are sensors of dawn and expression of <jats:italic>EOBII</jats:italic> also peaks at dawn, the prior is proposed to be part of the diurnal control of the volatile biosynthetic machinery. PhPIF4/5 was also found to transcriptionally activate <jats:italic>PhDELLA</jats:italic>s; a similar positive effect of PIFs on <jats:italic>DELLA</jats:italic> expression was further confirmed in <jats:italic>Arabidopsis</jats:italic> seedlings. The PhPIF4/5–PhDELLAs feedback is proposed to fine-tune GA signaling for regulation of floral scent production.</jats:p>