title: EGY1 encodes a membrane-associated and ATP-independent metalloprotease that is required for chloroplast development.
abstract: Chloroplast development requires coordinated expression of both nuclear- and chloroplast-encoded genes. To better understand the roles played by nuclear-encoded chloroplast proteins in chloroplast biogenesis, we isolated an Arabidopsis mutant, egy1-1, which has a dual phenotype, reduced chlorophyll accumulation and abnormal hypocotyl gravicurvature. Subsequent map-based cloning and DNA sequencing of the mutant gene revealed a 10-bp deletion in an EGY1 gene, which encodes a 59-kDa metalloprotease that contains eight trans-membrane domains at its C-terminus, and carries out beta-casein degradation in an ATP-independent manner. EGY1 protein accumulation varies between tissue types, being most prominent in leaf and stem tissues, and is responsive to light and ethylene. EGY1-GFP hybrid proteins are localized in the chloroplast. egy1 mutant chloroplasts had reduced granal thylakoids and poorly developed lamellae networks. Furthermore, the accumulation of chlorophyll a/b binding proteins of the light-harvesting complexes I and II (Lhca and Lhcb) are significantly decreased in three separate loss-of-function egy1 mutants. Taken together, these results suggest that EGY1 metalloprotease is required for chloroplast development and, hence, a defective EGY1 gene has pleiotropic effects both on chloroplast development and on ethylene-dependent gravitropism of light-grown hypocotyls.
authors.affiliation: Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
authors.forename: Gu
authors.initials: G
authors.lastname: Chen
authors.forename: Yu Rong
authors.initials: YR
authors.lastname: Bi
authors.forename: Ning
authors.initials: N
authors.lastname: Li
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology* / Q000502:physiology; D018522:Gravitropism / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D045726:Metalloproteases / Q000235:genetics* / Q000502:physiology; D010641:Phenotype; D010802:Phylogeny
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D002734:Chlorophyll; D000255:Adenosine Triphosphate; C500788:EGY1 protein, Arabidopsis; D045726:Metalloproteases