Phytochrome Interacting Factors

Lin LiChory’s lab

Content

• Members and structure

• mRNA level, protein level, phenotype of PIFs and PIFs mediated light signaling pathway

• Biological functions of PIFs

Plant Cell. 2008;20(2):337 Quail Lab

Plant Cell. 2004 ;16(11):3033 Quail Lab

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Cell. 1998 25;95(5):657

Nature. 1999 19;400(6746):781

Science. 2000 288(5467):859

PNAS. 2000 21;97(24):13419

Quail Lab

PIF3 was found using Y2H with PhyB C-term. PIF3 binds only the Pfr form, with 10 times more affinity to PhyB than to

PhyA. PIF3 binds to G-box. Phenotype show PIF3 is a positive regulator of Phy signaling.

EMBO J. 2002 21(10):2441 Quail lab

Mutant srl2 is short under red light , Mutation In PIF4 which can Bind G box. It is a negative regulator.

Plant Cell. 2003 15(10):2399Choi Lab Plant Cell. 2004;16(6):1433 Nagy LabPNAS. 2004 16;101(46):16091 Quail Lab

New PIF3 T-DNA show short hypocotyl under R and real FL OX show long hypocotyl. PIF3 is a negative regulators of Phy signaling. PIF3 is rapidly degraded by light.

Science. 2004 305(5692):1937Quail Lab

Indentification of the Phy binding motif (APB motif). Base on the sequence homology, PIF5 and PIF6 are identified.

Based on the premise that closely related proteins may have similar functions, a new bHLH family member PIF1 is identified

investigate members of the Arabidopsis bHLH subfamily 15 for possible involvement inphy signaling, characterized bHLH072 as PIF7

PIF family members

PIF7 At5g61270 bHLH72 +/- R Hypocotyl elongation

Cotyledon expansion

Trends Plant Sci. 2007 Nov;12(11):514

The APB motif is both necessary and sufficient for binding to the biologically active pfr form of phyB

The Plant Cell, 2004 Vol. 16, 3033

ELxxxxGQ

PIF7

Physical interactions of PIFs with phy and with other PIFs

Modify from Trends Plant Sci. 2007 Nov;12(11):514

PIF7

CACGTG

E-box: CANNTG

The Plant Cell, 2004 Vol. 16, 3033

PIF7 7 7

74

G-BOX

7 7

PIF4, PIF5 and PIF7 are light induced genes

PIF6

PIF1

PIF5

Plant Cell Physiol. 44(6): 619–629 (2003)

Plant Cell. 2008 ;20(2):33

Most PIFs are degraded in light condition except PIF7PIF1

PIF4 PIF5

PIF3

PIF7

All PIFs null lines show shorter hypocotyle and OX lines show taller hypocotyl phenotype

PIF1 PIF4 and PIF5PIF3

PIF7

Model of PIF function in phytochrome signaling pathways

Nature review 2007 Vol 8;217

Biological functions of PIF1

The Plant Cell, 2007 Vol. 19: 1192

PIF1 is involved in light-induced seed germination, light-induced inhibition of hypocotyl elongation, negative hypocotyl gravitropism in the Dark, Chlorophyll accumulation in light.

Biological functions of PIF3

PNAS 2009 Vol (106) 18; 7655

PIF3 is involved in light-induced inhibition of hypocotyl elongation, chloroplast development, light-induced accumulation of anthocyanin.

PIF4 is involved in hypocotyl elongation

Current Biology 2009 Vol 19 No 6

Nature 2008 Vol 451, 480

The Plant Journal (2009) 60, 589

A quadruple mutant (pifq) lacking four PIFs(PIF1, 3, 4, and 5) is constitutively photomorphogenic in darkness :

these factors sustain the skotomorphogenic state

The Plant Cell, 2009 Vol. 21: 3535

PIF6 is involved in seed dormancy

PIF6 is expressed strongly during seed development, and that two splice variants exist, one full length (the a form), and a second, the b form, in which a cryptic intron containing the potential DNA binding domain is spliced out, predicted to lead to the generation of a premature stop codon. Loss of PIF6 increases primary seed dormancy, whereas overexpression of the b form, but not the a form, reduce dormancy.

PIF7 is involved in hypocotyl elongation

Plant Physiology, 2009, Vol. 151, 2046

Open questions

• Identification target genes of PIFs

• How are PIFs involved in hormone signaling

• Regulation of PIFs function

• Circadian and PIFs