scholarly journals Two plastid POLLUX ion channel-like proteins are required for stress-triggered stromal Ca2+ release

2021 ◽  
Author(s):  
Carsten Völkner ◽  
Lorenz Josef Holzner ◽  
Philip M Day ◽  
Amra Dhabalia Ashok ◽  
Jan de Vries ◽  
...  
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Chloroplast Envelope ◽  
Mycorrhizal Symbiosis ◽  
Intermembrane Space ◽  
Envelope Membrane ◽  
Loss Of Function ◽  
Chloroplast Envelope Membrane ◽  
Envelope Membranes ◽  
Yeast Mutants

Abstract Two decades ago, large cation currents were discovered in the envelope membranes of Pisum sativum L. (pea) chloroplasts. The deduced K+-permeable channel was coined fast-activating chloroplast cation (FACC) channel but its molecular identity remained elusive. To reveal candidates, we mined proteomic datasets of isolated pea envelopes. Our search uncovered distant members of the nuclear POLLUX ion channel family. Since pea is not amenable to molecular genetics, we used Arabidopsis thaliana to characterize the two gene homologs. Using several independent approaches, we show that both candidates localize to the chloroplast envelope membrane. The proteins, designated PLASTID ENVELOPE ION CHANNELS (PEC1/2), form oligomers with regulator of K+ conductance (RCK) domains protruding into the intermembrane space. Heterologous expression of PEC1/2 rescues yeast mutants deficient in K+ uptake. Nuclear POLLUX ion channels cofunction with Ca2+ channels to generate Ca2+ signals, critical for establishing mycorrhizal symbiosis and root development. Chloroplasts also exhibit Ca2+ transients in the stroma, probably to relay abiotic and biotic cues between plastids and the nucleus via the cytosol. Our results show that pec1pec2 loss-of-function double mutants fail to trigger the characteristic stromal Ca2+ release observed in wild-type plants exposed to external stress stimuli. Besides this molecular abnormality, pec1pec2 double mutants do not show obvious phenotypes. Future studies of PEC proteins will help to decipher the plant’s stress-related Ca2+ signaling network and the role of plastids. More importantly, the discovery of PECs in the envelope membrane is another critical step towards completing the chloroplast ion transport protein inventory.

scholarly journals A Small ATPase Protein of Arabidopsis, TGD3, Involved in Chloroplast Lipid Import

2007 ◽  
Vol 282 (49) ◽  
pp. 35945-35953 ◽  
Author(s):  
Binbin Lu ◽  
Changcheng Xu ◽  
Koichiro Awai ◽  
A. Daniel Jones ◽  
Christoph Benning
Keyword(s):  
Endoplasmic Reticulum ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Coding Region ◽  
Lipid Trafficking ◽  
Final Destination ◽  
Dna Insertion ◽  
Chloroplast Envelope Membrane ◽  
Envelope Membranes ◽  
Thylakoid Lipids

Polar lipid trafficking is essential in eukaryotic cells as membranes of lipid assembly are often distinct from final destination membranes. A striking example is the biogenesis of the photosynthetic membranes (thylakoids) in plastids of plants. Lipid biosynthetic enzymes at the endoplasmic reticulum and the inner and outer plastid envelope membranes are involved. This compartmentalization requires extensive lipid trafficking. Mutants of Arabidopsis are available that are disrupted in the incorporation of endoplasmic reticulum-derived lipid precursors into thylakoid lipids. Two proteins affected in two of these mutants, trigalactosyldiacylglycerol 1 (TGD1) and TGD2, encode the permease and substrate binding component, respectively, of a proposed lipid translocator at the inner chloroplast envelope membrane. Here we describe a third protein of Arabidopsis, TGD3, a small ATPase proposed to be part of this translocator. As in the tgd1 and tgd2 mutants, triacylglycerols and trigalactolipids accumulate in a tgd3 mutant carrying a T-DNA insertion just 5′ of the TGD3 coding region. The TGD3 protein shows basal ATPase activity and is localized inside the chloroplast beyond the inner chloroplast envelope membrane. Proteins orthologous to TGD1, -2, and -3 are predicted to be present in Gram-bacteria, and the respective genes are organized in operons suggesting a common biochemical role for the gene products. Based on the current analysis, it is hypothesized that TGD3 is the missing ATPase component of a lipid transporter involving TGD1 and TGD2 required for the biosynthesis of ER-derived thylakoid lipids in Arabidopsis.

Ion Channels in the Chloroplast Envelope Membrane

Biochemistry ◽  
1995 ◽  
Vol 34 (49) ◽  
pp. 15906-15917 ◽  
Author(s):  
Thomas Heibert ◽  
Thomas Steinkamp ◽  
Silke Hinnah ◽  
Martin Schwarz ◽  
Ulf-Ingo Flueggel ◽  
...  
Keyword(s):  
Ion Channels ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Chloroplast Envelope Membrane

scholarly journals The transit sequence mediates the specific interaction of the precursor of ferredoxin with chloroplast envelope membrane lipids.

1993 ◽  
Vol 268 (6) ◽  
pp. 4037-4042
Author(s):  
R. van't Hof ◽  
W. van Klompenburg ◽  
M. Pilon ◽  
A. Kozubek ◽  
G. de Korte-Kool ◽  
...  
Keyword(s):  
Membrane Lipids ◽  
Specific Interaction ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Chloroplast Envelope Membrane

Mechanism of protein import across the chloroplast envelope

2000 ◽  
Vol 28 (4) ◽  
pp. 485-491 ◽  
Author(s):  
K. Chen ◽  
X. Chen ◽  
D. J. Schnell
Keyword(s):  
Protein Import ◽  
Essential Elements ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Subunits ◽  
Targeting Signals ◽  
Outer Envelope Membrane ◽  
Envelope Membranes

The development and maintenance of chloroplasts relies on the contribution of protein subunits from both plastid and nuclear genomes. Most chloroplast proteins are encoded by nuclear genes and are post-translationally imported into the organelle across the double membrane of the chloroplast envelope. Protein import into the chloroplast consists of two essential elements: the specific recognition of the targeting signals (transit sequences) of cytoplasmic preproteins by receptors at the outer envelope membrane and the subsequent translocation of preproteins simultaneously across the double membrane of the envelope. These processes are mediated via the co-ordinate action of protein translocon complexes in the outer (Toe apparatus) and inner (Tic apparatus) envelope membranes.

scholarly journals Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana

2016 ◽  
Vol 113 (38) ◽  
pp. 10714-10719 ◽  
Author(s):  
Amélie A. Kelly ◽  
Barbara Kalisch ◽  
Georg Hölzl ◽  
Sandra Schulze ◽  
Juliane Thiele ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Lipid Transfer ◽  
Terminal Sequence ◽  
Outer Envelope ◽  
Outer Envelope Membrane ◽  
Envelope Reconstruction ◽  
Envelope Membranes

Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.

How SFR2 is regulated to confer freezing tolerance of the chloroplast envelope membrane

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Rebecca L. Roston ◽  
Allison C. Barnes ◽  
Zachary Shomo ◽  
Samantha Surber ◽  
Jennifer Myers
Keyword(s):  
Freezing Tolerance ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Chloroplast Envelope Membrane

scholarly journals Redox Transfer across the Inner Chloroplast Envelope Membrane

1991 ◽  
Vol 95 (4) ◽  
pp. 1131-1137 ◽  
Author(s):  
Dieter Heineke ◽  
Burgi Riens ◽  
Heike Grosse ◽  
Petra Hoferichter ◽  
Ute Peter ◽  
...  
Keyword(s):  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Chloroplast Envelope Membrane

scholarly journals Functional Analysis of Rice Long-Chain Acyl-CoA Synthetase 9 (OsLACS9) in the Chloroplast Envelope Membrane

2020 ◽  
Vol 21 (6) ◽  
pp. 2223
Author(s):  
Aya Kitajima-Koga ◽  
Marouane Baslam ◽  
Yuuki Hamada ◽  
Namiko Ito ◽  
Tomoko Taniuchi ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Fatty Acyl ◽  
Laser Scanning Microscopy ◽  
Chloroplast Envelope ◽  
Confocal Laser ◽  
Starch Degradation ◽  
Envelope Membrane ◽  
Chain Acyl ◽  
Chloroplast Envelope Membrane ◽  
Long Chain

The long-chain acyl-CoA synthetases (LACSs) are involved in lipid synthesis, fatty acid catabolism, and the transport of fatty acids between subcellular compartments. These enzymes catalyze the critical reaction of fatty acyl chains to fatty acyl-CoAs for the triacylglycerol biosynthesis used as carbon and energy reserves. In Arabidopsis, LACSs are encoded by a family of nine genes, with LACS9 being the only member located in the chloroplast envelope membrane. However, the comprehensive role of LACS9 and its contribution to plant metabolism have not been explored thoroughly. In this study, we report on the identification and characterization of LACS9 mutants in rice plants. Our results indicate that the loss-of-function mutations in OsLACS9 affect the architecture of internodes resulting in dwarf plants with large starch granules in the chloroplast, showing the suppression of starch degradation. Moreover, the plastid localization of α-amylase I-1 (AmyI-1)—a key enzyme involved in starch breakdown in plastids—was suppressed in the lacs9 mutant line. Immunological and confocal laser scanning microscopy analyses showed that OsLACS9-GFP is located in the chloroplast envelope in green tissue. Microscopic analysis showed that OsLACS9s interact with each other in the plastid envelope membrane. Furthermore, OsLACS9 is also one of the proteins transported to plastids without a transit peptide or involvement of the Toc/Tic complex system. To identify the plastid-targeting signal of OsLACS9, the transient expression and localization of a series of N-terminal truncated OsLACS9-green fluorescent protein (GFP) fusion proteins were examined. Truncation analyses identified the N-terminal 30 amino acid residues to be required for OsLACS9 plastid localization. Overall, the data in this study provide an advanced understanding of the function of OsLACS9 and its role in starch degradation and plant growth.

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