title: Transient accumulation of Mg-protoporphyrin IX regulates expression of PhANGs - New evidence for the signaling role of tetrapyrroles in mature Arabidopsis plants.
abstract: Genetic and physiological studies have revealed evidence for multiple signaling pathways by which the plastid exerts retrograde control over photosynthesis associated nuclear genes (PhANGs). It has been proposed that the tetrapyrrole pathway intermediate Mg-protoporphyrin IX (Mg-proto IX) acts as the signaling molecule in the pathways and accumulates in the chloroplasts and cytosol of the cell after treatment with the herbicide Norflurazon (NF). However, the role of Mg-Proto IX in plastid signaling has been challenged by two recent reports. In this paper, new evidence is presented supporting Mg-Proto IX as a plastid-signaling molecule in mature Arabidopsis seedlings. Fluorescence HPLC and confocal microscope observation verified that a short-term (<96h) NF treatment resulted in a large accumulation of Mg-Proto IX accompanying with Lhcb repression, whereas the long-term NF treatments caused marked changes of tetrapyrrole pools, while Lhcb expression was continuously repressed. These results may explain the discrepancies among different reports. Reactive oxygen species (ROS) eliminator treatments only partly reversed the NF-induced repression of Lhcb. Therefore, the NF generates both ROS signals and Mg-Proto IX signals. Furthermore, our data suggested that plastid signal transduction through plastid GUN1 protein is independent of tetrapyrrole export from the plastid.
authors.affiliation: Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China.
authors.forename: Zhong-Wei
authors.initials: ZW
authors.lastname: Zhang
authors.forename: Shu
authors.initials: S
authors.lastname: Yuan
authors.forename: Hong
authors.initials: H
authors.lastname: Feng
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.forename: Jian
authors.initials: J
authors.lastname: Cheng
authors.forename: Jing
authors.initials: J
authors.lastname: Shang
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Zhang
authors.forename: Hong-Hui
authors.initials: HH
authors.lastname: Lin
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D018613:Microscopy, Confocal; D011524:Protoporphyrins / Q000378:metabolism*; D011724:Pyridazines / Q000633:toxicity; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D045725:Tetrapyrroles / Q000378:metabolism*
chemical_list: D011524:Protoporphyrins; D011724:Pyridazines; D017382:Reactive Oxygen Species; D045725:Tetrapyrroles; C039629:magnesium protoporphyrin; C008677:norflurazone