title: Plastid intramembrane proteolysis.
abstract: Progress in the field of regulated intramembrane proteolysis (RIP) in recent years has not surpassed plant biology. Nevertheless, reports on RIP in plants, and especially in chloroplasts, are still scarce. Of the four different families of intramembrane proteases, only two have been linked to chloroplasts so far, rhomboids and site-2 proteases (S2Ps). The lack of chloroplast-located rhomboid proteases was associated with reduced fertility and aberrations in flower morphology, probably due to perturbations in jasmonic acid biosynthesis, which occurs in chloroplasts. Mutations in homologues of S2P resulted in chlorophyll deficiency and impaired chloroplast development, through a yet unknown mechanism. To date, the only known substrate of RIP in chloroplasts is a PHD transcription factor, located in the envelope. Upon proteolytic cleavage by an unknown protease, the soluble N-terminal domain of this protein is released from the membrane and relocates to the nucleus, where it activates the transcription of the ABA response gene ABI4. Continuing studies on these proteases and substrates, as well as identification of the genes responsible for different chloroplast mutant phenotypes, are expected to shed more light on the roles of intramembrane proteases in chloroplast biology.
authors.affiliation: The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel. Electronic address: zach.adam@mail.huji.ac.il.
authors.forename: Zach
authors.initials: Z
authors.lastname: Adam
mesh_terms: D008565:Membrane Proteins / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000502:physiology; D018087:Plastids / Q000378:metabolism*; D059748:Proteolysis
chemical_list: D008565:Membrane Proteins; D010447:Peptide Hydrolases
keywords: Chloroplast; Protease; Rhomboid protease; Site-2 protease