title: The cold-inducible CBF1 factor-dependent signaling pathway modulates the accumulation of the growth-repressing DELLA proteins via its effect on gibberellin metabolism.
abstract: Plants have evolved robust mechanisms to respond and adapt to unfavorable environmental conditions, such as low temperature. The C-repeat/drought-responsive element binding factor CBF1/DREB1b gene encodes a transcriptional activator transiently induced by cold that controls the expression of a set of genes responding to low temperature (the CBF regulon). Constitutive expression of CBF1 confers freezing tolerance but also slows growth. Here, we propose that low temperature-induced CBF1 expression restrains growth at least in part by allowing the accumulation of DELLAs, a family of nuclear growth-repressing proteins, the degradation of which is stimulated by gibberellin (GA). We show that cold/CBF1 enhances the accumulation of a green fluorescent protein (GFP)-tagged DELLA protein (GFP-RGA) by reducing GA content through stimulating expression of GA-inactivating GA 2-oxidase genes. Accordingly, transgenic plants that constitutively express CBF1 accumulate less bioactive GA and as a consequence exhibit dwarfism and late flowering. Both phenotypes are suppressed when CBF1 is expressed in a line lacking two DELLA proteins, GA-INSENSITIVE and REPRESSOR OF GA1-3. In addition, we show that DELLAs contribute significantly to CBF1-induced cold acclimation and freezing tolerance by a mechanism that is distinct from the CBF regulon. We conclude that DELLAs are components of the CBF1-mediated cold stress response.
authors.affiliation: Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventioné avec l'Université Louis Pasteur, 67084 Strasbourg, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Achard
authors.forename: Fan
authors.initials: F
authors.lastname: Gong
authors.forename: Soizic
authors.initials: S
authors.lastname: Cheminant
authors.forename: Malek
authors.initials: M
authors.lastname: Alioua
authors.forename: Peter
authors.initials: P
authors.lastname: Hedden
authors.forename: Pascal
authors.initials: P
authors.lastname: Genschik