Identification of Putative Substrates of SEC2, a Chloroplast Inner Envelope Translocase

Li, Yubing; Martin, Jonathan H.; Aldama, Giovanni A; Fernandez, Donna E.; Cline, Kenneth

doi:10.1104/pp.17.00012

Cited by 32 publications

(27 citation statements)

References 60 publications

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“…After import, intact chloroplast were recovered, lysed and applied to a sucrose step‐gradient according to the method of Li et al . () and fractionated into envelope membranes (E), stroma (S) and thylakoid membranes (T). All fractions were analyzed by SDS‐PAGE and fluorography.…”

Section: Methodsmentioning

confidence: 99%

A predicted plastid rhomboid protease affects phosphatidic acid metabolism in Arabidopsis thaliana

et al. 2019

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Summary The thylakoid membranes of the chloroplast harbor the photosynthetic machinery that converts light into chemical energy. Chloroplast membranes are unique in their lipid makeup, which is dominated by the galactolipids mono‐ and digalactosyldiacylglycerol (MGDG and DGDG). The most abundant galactolipid, MGDG, is assembled through both plastid and endoplasmic reticulum (ER) pathways in Arabidopsis, resulting in distinguishable molecular lipid species. Phosphatidic acid (PA) is the first glycerolipid formed by the plastid galactolipid biosynthetic pathway. It is converted to substrate diacylglycerol (DAG) for MGDG Synthase (MGD1) which adds to it a galactose from UDP‐Gal. The enzymatic reactions yielding these galactolipids have been well established. However, auxiliary or regulatory factors are largely unknown. We identified a predicted rhomboid‐like protease 10 (RBL10), located in plastids of Arabidopsis thaliana, that affects galactolipid biosynthesis likely through intramembrane proteolysis. Plants with T‐DNA disruptions in RBL10 have greatly decreased 16:3 (acyl carbons:double bonds) and increased 18:3 acyl chain abundance in MGDG of leaves. Additionally, rbl10‐1 mutants show reduced [14C]–acetate incorporation into MGDG during pulse−chase labeling, indicating a reduced flux through the plastid galactolipid biosynthesis pathway. While plastid MGDG biosynthesis is blocked in rbl10‐1 mutants, they are capable of synthesizing PA, as well as producing normal amounts of MGDG by compensating with ER‐derived lipid precursors. These findings link this predicted protease to the utilization of PA for plastid galactolipid biosynthesis potentially revealing a regulatory mechanism in chloroplasts.

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Section: Methodsmentioning

confidence: 99%

A predicted plastid rhomboid protease affects phosphatidic acid metabolism in Arabidopsis thaliana

et al. 2019

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“…The chloroplast SRP (cpSRP) interacts with the cpSRP receptor cpFtsY and the insertase ALB3 to insert nucleus-encoded light-harvesting complex proteins into the thylakoid membrane (reviewed in Ziehe et al, 2017). Some proteins apparently insert spontaneously into the thylakoid membrane; finally, a recently discovered parallel Sec pathway targets proteins to the inner envelope membrane (Li et al, 2017b).…”

Section: Cotranslational Folding Maturation Targeting and Assemblymentioning

confidence: 99%

Chloroplast Translation: Structural and Functional Organization, Operational Control, and Regulation

2018

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Chloroplast translation is essential for cellular viability and plant development. Its positioning at the intersection of organellar RNA and protein metabolism makes it a unique point for the regulation of gene expression in response to internal and external cues. Recently obtained high-resolution structures of plastid ribosomes, the development of approaches allowing genome-wide analyses of chloroplast translation (i.e., ribosome profiling), and the discovery of RNA binding proteins involved in the control of translational activity have greatly increased our understanding of the chloroplast translation process and its regulation. In this review, we provide an overview of the current knowledge of the chloroplast translation machinery, its structure, organization, and function. In addition, we summarize the techniques that are currently available to study chloroplast translation and describe how translational activity is controlled and which -elements and-factors are involved. Finally, we discuss how translational control contributes to the regulation of chloroplast gene expression in response to developmental, environmental, and physiological cues. We also illustrate the commonalities and the differences between the chloroplast and bacterial translation machineries and the mechanisms of protein biosynthesis in these two prokaryotic systems.

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“…Entry into the chloroplast is achieved via translocon complexes in the outer (TOC) and inner (TIC) envelope membranes, which recognize the TP and facilitate transport into the stroma. The TPs of translocated precursor proteins ( pre-proteins) are then cleaved off by the stromal processing peptidase (SPP) [12], before final folding and assembly in the stroma, or onward routing to the thylakoids [13,14] or the inner envelope membrane (IEM) [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Protein import into chloroplasts and its regulation by the ubiquitin-proteasome system

Thomson

Pulido

Jarvis

2020

Biochemical Society Transactions

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Chloroplasts are photosynthetic plant organelles descended from a bacterial ancestor. The vast majority of chloroplast proteins are synthesized in the cytosol and then imported into the chloroplast post-translationally. Translocation complexes exist in the organelle's outer and inner envelope membranes (termed TOC and TIC, respectively) to facilitate protein import. These systems recognize chloroplast precursor proteins and mediate their import in an energy-dependent manner. However, many unanswered questions remain regarding mechanistic details of the import process and the participation and functions of individual components; for example, the cytosolic events that mediate protein delivery to chloroplasts, the composition of the TIC apparatus, and the nature of the protein import motor all require resolution. The flux of proteins through TOC and TIC varies greatly throughout development and in response to specific environmental cues. The import process is, therefore, tightly regulated, and it has emerged that the ubiquitin-proteasome system (UPS) plays a key role in this regard, acting at several different steps in the process. The UPS is involved in: the selective degradation of transcription factors that co-ordinate the expression of chloroplast precursor proteins; the removal of unimported chloroplast precursor proteins in the cytosol; the inhibition of chloroplast biogenesis pre-germination; and the reconfiguration of the TOC apparatus in response to developmental and environmental signals in a process termed chloroplast-associated protein degradation. In this review, we highlight recent advances in our understanding of protein import into chloroplasts and how this process is regulated by the UPS.

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Identification of Putative Substrates of SEC2, a Chloroplast Inner Envelope Translocase

Cited by 32 publications

References 60 publications

A predicted plastid rhomboid protease affects phosphatidic acid metabolism in Arabidopsis thaliana

A predicted plastid rhomboid protease affects phosphatidic acid metabolism in Arabidopsis thaliana

Chloroplast Translation: Structural and Functional Organization, Operational Control, and Regulation

Protein import into chloroplasts and its regulation by the ubiquitin-proteasome system

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