Table 1.

Characterization of the selected transcription factors and the TFBSs with unknown transcription factors that were identified in the promoter regions of the Ppd-1 genes

Family	Transcription factors/TFBSs with unknown TF	Description
Phytochrome regulated transcription factors
VOZ	VOZ2	VOZ2 was identified as one of the highly conserved transcriptional factors in land plant genes that are PhyB-interacting factors [58].
bHLH	Phytochrome Interacting Factor3 (PIF3)	The G-box, CACGTG, is a target sequence for PIF3 [59]. PIF3 plays important roles in the Phy-mediated light responses. This factor can regulate the downstream genes either positively or negatively [60]. In Arabidopsis, PIF3 was suggested to play an important role in the control of flowering by the regulation of CO and FT gene expression [61].
bHLH	Phytochrome Interacting Factor3-Like5 (PIL1)	PIL5 interacts with the Pfr forms of Phytochrome A (PhyA) and Phytochrome B (PhyB) [62].
FAR1	Far-Red Elongated Hypokotyls3/Far-Red-Impaired Response1 (FHY3/FAR1)	Transcription factor FHY3/FAR1 modulates PhyA-signaling in higher plants [63]. Other investigations demonstrated that FHY3 plays a principal role in the circadian clock, heading date control and regulation of heading time through ELF4 (EARLY FLOWERING4) [64].
Myb/SANT; MYB-related	RVE7/EPR1	RVE7/EPR1 is regulated by both PhyA and PhyB and negatively regulates flowering [65].
–	SORLIP2AT and SORLIP1AT	Sequences over-represented in the light-induced promoters SORLIP2AT and SORLIP1AT were identified in the PhyA-induced promoters [66].
–	RE1ASPHYA3	RE1ASPHYA3 (RE1, putative repressor element) is a highly conserved motif in the most monocot PhyA promoters and is responsible for the Pfr-directed repression [67]; this motif was detected in certain other genes [68].
Circadian-clock regulated transcription factors
AP2/RAV/B3	RAV1	RAV1 is a negative component in the regulation of plant development [69].
AP2/RAV/B3	TEMPRANILLO1 (TEM1) TEMPRANILLO2 (TEM2)	TEM1 and TEM2 genes act as direct repressors of FT [70].
MYB-related	REVEILLE1 (RVE1)	RVE1 is a morning-phased transcription factor that integrates the circadian clock and auxin pathways [71].
Myb/SANT; MYB-related	REVEILLE 8 (RVE8)	RVE8 promotes the expression of some evening element that contains clock genes and forms a negative feedback loop with PRR5 [72, 73].
MYB	Circadian Clock Associated 1 (CCA1); Late Elongated Hypocotyl (LHY)	The MYB transcription factors CCA1 and LHY are some of the key genes in the central oscillator of the plant circadian clock [74]. LHY and CCA1 negatively regulate TOC1 expression.
TCP	CCA1 HIKING EXPEDITION (CHE)	The TCP transcription factor CHE is a clock component that is partially redundant with LHY in the repression of CCA1 [75].
Other light regulated transcription factors
GATA/tify	GATA2	GATA2 directly regulates genes that respond to light [76].
GATA/tify	GATA12	GATA12 is involved in the regulation of many light-responsive genes [77, 78].
MADF; Trihelix	GT-1	GT-1 may act as a light-responsive transcription factor [79].
bHLH	AtMYC2	AtMYC2 acts as a negative regulator of blue light–mediated photomorphogenic growth and blue and far-red-light–regulated gene expression [80].
–	BOXIIPCCHS	BOXIIPCCHS was suggested to be essential for light regulation [29, 81].
–	TBOXATGAPB	Mutations in TBOXATGAPB cause a reduction in light-activated transcription [82, 83].
–	IBOXCORENT	I-box core motif IBOXCORENT in the conserved DNA modular arrays is associated with the light-responsive promoter regions [84].
–	LREBOXIIPCCHS1	Light responsive element LREBOXIIPCCHS1, which was detected in parsley, is required for light responsiveness [85].
–	IBOXCORE	Conserved sequence in the 5′ UTR of light-regulated genes IBOXCORE may be involved in the regulation of transcription by light and the circadian clock. This sequence was detected in both monocots and dicots [86].