title: EIN3/EIL1 cooperate with PIF1 to prevent photo-oxidation and to promote greening of Arabidopsis seedlings.
abstract: The ability to switch from skotomorphogenesis to photomorphogenesis is essential for seedling development and plant survival. Recent studies revealed that COP1 and phytochrome-interacting factors (PIFs) are key regulators of this transition by repressing the photomorphogenic responses and/or maintaining the skotomorphogenic state of etiolated seedlings. Here we report that the plant hormone ethylene plays a crucial role in the transition from skotomorphogenesis to photomorphogenesis by facilitating greening of etiolated seedlings upon light irradiation. Activation of EIN3/EIL1 is both necessary and sufficient for ethylene-induced enhancement of seedling greening, as well as repression of the accumulation of protochlorophyllide, a phototoxic intermediate of chlorophyll synthesis. EIN3/EIL1 were found to induce gene expression of two key enzymes in the chlorophyll synthesis pathway, protochlorophyllide oxidoreductase A and B (PORA/B). ChIP and EMSA assays demonstrated that EIN3 directly binds to the specific elements present in the PORA and PORB promoters. Genetic studies revealed that EIN3/EIL1 function in cooperation with PIF1 in preventing photo-oxidative damage and promoting cotyledon greening. Moreover, activation of EIN3 reverses the blockage of greening triggered by cop1 mutation or far-red light irradiation. Consistently, EIN3 acts downstream of COP1 and its protein accumulation is enhanced by COP1 but decreased by light. Taken together, EIN3/EIL1 represent a new class of transcriptional regulators along with PIF1 to optimize de-etiolation of Arabidopsis seedlings. Our study highlights the essential role of ethylene in enhancing seedling development and survival through protecting etiolated seedlings against photo-oxidative damage.
authors: National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
authors: Shangwei
authors: S
authors: Zhong
authors: Mantong
authors: M
authors: Zhao
authors: Tianying
authors: T
authors: Shi
authors: Hui
authors: H
authors: Shi
authors: Fengying
authors: F
authors: An
authors: Qiong
authors: Q
authors: Zhao
authors: Hongwei
authors: H
authors: Guo
mesh_terms: D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D002734:Chlorophyll / Q000096:biosynthesis*; D004268:DNA-Binding Proteins; D008027:Light; D009687:Nuclear Proteins / Q000502:physiology*; D010084:Oxidation-Reduction; D010788:Photosynthesis; D036226:Seedlings / Q000254:growth & development* / Q000528:radiation effects; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002734:Chlorophyll; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C494589:EIL1 protein, Arabidopsis; C106987:EIN3 protein, Arabidopsis; C508068:At2g20180 protein, Arabidopsis