Blue Rhythms Between GIGANTEA and Phytochromes.
GIGANTEA (GI) is involved in the promotion of flowering by long days, in light input to the circadian clock, and in seedling de-etiolation under continuous red light or blue light but not under continuous far-red light (FR). Since red-light effects are mediated largely by phytochrome B and those of FR by phytochrome A (phyA), GI was considered not to affect phyA signaling. However, recent observations using brief FR pulses indicate that GI does affect the very-low-fluence response (VLFR) and not the high-irradiance response (HIR) pathway of phyA. Seed germination, seedling de-etiolation and gene expression showed rhythmic sensitivity to FR pulses. GI affected the magnitude but not the rhythmic pattern of the responses, indicating that GI regulation of phyA signaling does not derive from its effects on the clock. Here we show that despite de above divergence between VLFR and HIR, both pathways require the bZip transcription factor HY5. Furthermore, the blue-light phenotype of gi is not mediated by phyA, indicating a role of GI in the control of cryptochrome signaling. These findings illustrate features of plant signaling networks.
Crepy
María
M
IFEVA; Facultad de Agronomía; Universidad de Buenos Aires; CONICET; Buenos Aires, Argentina.
Yanovsky
Marcelo J
MJ
Casal
Jorge J
JJ
Plant Cell. 1998 May;10(5):673-83
9596629
Plant Physiol. 2007 Jan;143(1):473-86
17098855
Plant Physiol. 2007 May;144(1):495-502
17384162
Planta. 2006 Nov;224(6):1255-68
16775702
Proc Natl Acad Sci U S A. 1996 Jul 23;93(15):8129-33
8755615
Plant Cell. 2000 Jul;12(7):1203-11
10899984
Plant J. 1999 Jan;17(1):63-71
10069068
Plant Cell. 2005 Aug;17(8):2255-70
16006578
Plant J. 1998 Jun;14(6):759-64
9681039
Plant Cell. 2004 Jun;16(6):1550-63
15155885
Plant Cell. 2002 Jul;14(7):1591-603
12119377
Science. 1999 Sep 3;285(5433):1579-82
10477524
Photochem Photobiol. 2000 Apr;71(4):481-6
10824602
Proc Natl Acad Sci U S A. 2000 Aug 15;97(17):9789-94
10920210
Plant Cell. 1995 Oct;7(10):1703-1712
12242359
Plant Cell. 2003 Dec;15(12):2966-78
14615593
Plant Physiol. 1996 Feb;110(2):439-444
12226195
Science. 1995 May 5;268(5211):675-80
7732376
Plant Physiol. 2000 Jan;122(1):147-56
10631258
Plant J. 2003 Jun;34(6):827-36
12795702
EMBO J. 1999 Sep 1;18(17):4679-88
10469647