Identification and characterization of Cor413im proteins as novel components of the chloroplast inner envelope

Abstract

Plastids are surrounded by two membrane layers, the outer and inner envelope membranes, which have various transport and metabolic activities. A number of envelope membrane proteins have been identified by biochemical approaches and have been assigned to specific functions. Despite those efforts, the chloroplast envelope membrane is expected to contain a number of as yet unidentified proteins that may affect specific aspects of plant growth and development. In this report, we identify and characterize a novel class of inner envelope membrane proteins, designated as Cor413 chloroplast inner envelope membrane group (Cor413im). Both in vivo and in vitro studies indicate that Cor413im proteins are targeted to the chloroplast envelope. Biochemical analyses of Cor413im1 demonstrate that it is an integral membrane protein in the inner envelope of chloroplasts. Quantitative real-time PCR analysis reveals that COR413IM1 is more abundant than COR413IM2 in cold-acclimated Arabidopsis leaves. The analyses of T-DNA insertion mutants indicate that a single copy of COR413IM genes is sufficient to provide normal freezing tolerance to Arabidopsis. Based on these data, we propose that Cor413im proteins are novel components that are targeted to the chloroplast inner envelope in response to low temperature.

Ubiquitin-Proteasome Dependent Regulation of the GOLDEN2-LIKE 1 Transcription Factor in Response to Plastid Signals

“…Then, the supernatant was mixed with an equal volume of buffer containing 2% Triton X-100 to solubilize membranes, and centrifuged at 20,000g for 10 min. The resulting supernatant was resolved on a Sephacryl S-300HR column equilibrated with TES buffer containing 0.1% Triton X-100 (Okawa et al, 2008) using an AKTA-prime chromatography system (GE Healthcare). The first 30 mL of eluate were discarded as void volume because we did not observe any A 280 .…”

Opposing control by transcription factors MYB61 and MYB3 Increases Freezing Tolerance by relieving C-repeat Binding Factor suppression

“…Among these, several genes are linked to cold stress responses. For example, MtCOR413 (Medtr4g068520) is involved in maintaining membrane function and integrity under low-temperature stress to limit damaging cell membranes (Breton et al, 2003;Okawa et al, 2008). MtLTI6A (for low temperature-induced protein; Medtr7g111380) and MtLTI6B (Medtr7g111350) regulate the membrane potential (Medina et al, 2001).…”

Bilateral Communication between Plastid and the Nucleus: Plastid Protein Import and Plastid-to-Nucleus Retrograde Signaling

“…When the plastid is dysfunctional, induction of cold-regulated genes, such as COR15A 75,76) or COR413IM 77) in Arabidopsis or cor14b, tmc-ap3, or blt14 in barley, 78,79) is significantly impaired. Likewise, manipulation of the plastid signaling pathway by overexpression of GLK1 resulted in the induction of COR15A.…”