EGY1 encodes a membrane-associated and ATP-independent metalloprotease that is required for chloroplast development

• Published in: The Plant journal : for cell and molecular biology 2005-02, Vol.41 (3), p.364-375
• Main Authors: Chen, G, Bi, Y.R, Li, N
• Format: Article
• Language: English
• Subjects: adenosine triphosphate; Adenosine Triphosphate - metabolism; Arabidopsis; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - ultrastructure; Arabidopsis Proteins - genetics; Arabidopsis Proteins - physiology; Arabidopsis thaliana; Biological and medical sciences; Botany; Cell structures and functions; Chlorophyll; Chlorophyll - metabolism; chloroplast development; Chloroplast, photosynthetic membrane and photosynthesis; chloroplasts; Chloroplasts - enzymology; Chloroplasts - physiology; complementary DNA; EGY1; Enzymes; ethylene-depedent gravitropism-deficient and yellow-green 1 gene; ethylene‐dependent gravitropism; Flowers & plants; Fundamental and applied biological sciences. Psychology; Genes; Gravitropism - genetics; membrane proteins; Membrane Proteins - genetics; Membrane Proteins - physiology; membrane‐associated metalloprotease; Metalloproteases - genetics; Metalloproteases - physiology; metalloproteinases; Molecular and cellular biology; molecular sequence data; mutants; Mutation; nucleotide sequences; Phenotype; phenotypic variation; Phylogeny; plant morphology; plant proteins; Proteins; recombinant fusion proteins; sequence analysis; tissue distribution; yellow‐green
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2004.02308.x

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.