title: Thioredoxin redox regulates ATPase activity of magnesium chelatase CHLI subunit and modulates redox-mediated signaling in tetrapyrrole biosynthesis and homeostasis of reactive oxygen species in pea plants.
abstract: The chloroplast thioredoxins (TRXs) function as messengers of redox signals from ferredoxin to target enzymes. In this work, we studied the regulatory impact of pea (Pisum sativum) TRX-F on the magnesium (Mg) chelatase CHLI subunit and the enzymatic activation of Mg chelatase in vitro and in vivo. In vitro, reduced TRX-F activated the ATPase activity of pea CHLI and enhanced the activity of Mg chelatase reconstituted from the three recombinant subunits CHLI, CHLD, and CHLH in combination with the regulator protein GENOMES UNCOUPLED4 (GUN4). Yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that TRX-F physically interacts with CHLI but not with either of the other two subunits or GUN4. In vivo, virus-induced TRX-F gene silencing (VIGS-TRX-F) in pea plants did not result in an altered redox state of CHLI. However, simultaneous silencing of the pea TRX-F and TRX-M genes (VIGS-TRX-F/TRX-M) resulted in partially and fully oxidized CHLI in vivo. VIGS-TRX-F/TRX-M plants demonstrated a significant reduction in Mg chelatase activity and 5-aminolevulinic acid synthesizing capacity as well as reduced pigment content and lower photosynthetic capacity. These results suggest that, in vivo, TRX-M can compensate for a lack of TRX-F and that both TRXs act as important redox regulators of Mg chelatase. Furthermore, the silencing of TRX-F and TRX-M expression also affects gene expression in the tetrapyrrole biosynthesis pathway and leads to the accumulation of reactive oxygen species, which may also serve as an additional signal for the transcriptional regulation of photosynthesis-associated nuclear genes.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Luo
authors.forename: Tingting
authors.initials: T
authors.lastname: Fan
authors.forename: Yinan
authors.initials: Y
authors.lastname: Liu
authors.forename: Maxi
authors.initials: M
authors.lastname: Rothbart
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.forename: Shuaixiang
authors.initials: S
authors.lastname: Zhou
authors.forename: Bernhard
authors.initials: B
authors.lastname: Grimm
authors.forename: Meizhong
authors.initials: M
authors.lastname: Luo
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D060054:Agrobacterium / Q000235:genetics / Q000378:metabolism; D000622:Aminolevulinic Acid / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D054479:Chloroplast Thioredoxins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D020868:Gene Silencing; D017343:Genes, Plant; D006706:Homeostasis; D008190:Lyases / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010788:Photosynthesis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D025941:Protein Interaction Mapping; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D045725:Tetrapyrroles / Q000096:biosynthesis*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: D054479:Chloroplast Thioredoxins; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D045725:Tetrapyrroles; D002734:Chlorophyll; D000622:Aminolevulinic Acid; D000251:Adenosine Triphosphatases; D008190:Lyases; C086788:magnesium chelatase