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Title: A Stromal Heat Shock Protein 70 System Functions in Protein Import into Chloroplasts in the Moss Physcomitrella patens

Journal Article · · The Plant Cell
 [1];  [2]
  1. Univ. of California, Davis, CA (United States); University of California - Davis
  2. Univ. of California, Davis, CA (United States)
+ Show Author Affiliations

Heat shock protein 70s (Hsp70s) are encoded by a multigene family and are located in different cellular compartments. They have broad-ranging functions, including involvement in protein trafficking, prevention of protein aggregation, and assistance in protein folding. Hsp70s work together with their cochaperones, J domain proteins and nucleotide exchange factors (e.g., GrpEs), in a functional cycle of substrate binding and release accompanied by ATP hydrolysis. We have taken advantage of the gene targeting capability of the moss Physcomitrella patens to investigate the functions of chloroplast Hsp70s. We identified four Hsp70 genes and two GrpE cochaperone homolog genes (CGE) in moss that encode chloroplast proteins. Disruption of one of the Hsp70 genes, that for Hsp70-2, caused lethality, and protein import into heat-shocked chloroplasts isolated from temperature-sensitive hsp70-2 mutants was appreciably impaired. Whereas the double cge null mutant was not viable, we recovered a cge1 null/cge2 knock down mutant in which Hsp70-2 was upregulated. Chloroplasts isolated from this mutant demonstrated a defect in protein import. In addition, two different precursors staged as early import intermediates could be immunoprecipitated with an Hsp70-2-specific antibody. Furthermore, this immunoprecipitate also contained Hsp93 and Tic40, indicating that it represents a precursor still in the Toc/Tic translocon. Together, these data indicate that a stromal Hsp70 system plays a crucial role in protein import into chloroplasts.

Research Organization:
Univ. of California, Davis, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Grant/Contract Number:
FG02-03ER15405
OSTI ID:
1490440
Journal Information:
The Plant Cell, Journal Name: The Plant Cell Journal Issue: 1 Vol. 22; ISSN 1040-4651
Publisher:
American Society of Plant Biologists (ASPB)Copyright Statement
Country of Publication:
United States
Language:
English

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Sequence analysis of the Hsp70 family in moss and evaluation of their functions in abiotic stress responses journal September 2016
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Corrigendum for: Plastid casein kinase 2 knockout reduces abscisic acid (ABA) sensitivity, thermotolerance, and expression of ABA- and heat-stress-responsive nuclear genes journal August 2015
Structural characterizations of the chloroplast translocon protein Tic110 journal June 2013
Roles of Hsp70s in Stress Responses of Microorganisms, Plants, and Animals journal January 2015
Specific Hsp100 Chaperones Determine the Fate of the First Enzyme of the Plastidial Isoprenoid Pathway for Either Refolding or Degradation by the Stromal Clp Protease in Arabidopsis journal January 2016
Interference with plastome gene expression and Clp protease activity in Arabidopsis triggers a chloroplast unfolded protein response to restore protein homeostasis journal September 2017
Long-term boron-deficiency-responsive genes revealed by cDNA-AFLP differ between Citrus sinensis roots and leaves journal July 2015
Import of Soluble Proteins into Chloroplasts and Potential Regulatory Mechanisms journal February 2017
Two Arabidopsis Chloroplast GrpE Homologues Exhibit Distinct Biological Activities and Can Form Homo- and Hetero-Oligomers journal January 2020
Genome-Wide Characterization of Heat-Shock Protein 70s from Chenopodium quinoa and Expression Analyses of Cqhsp70s in Response to Drought Stress journal January 2018
PpSARK Regulates Moss Senescence and Salt Tolerance through ABA Related Pathway journal September 2018
Additional file 12 of Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens dataset January 2020
Additional file 4 of Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens dataset January 2020
Additional file 5 of Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens dataset January 2020
Additional file 6 of Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens dataset January 2020
Additional file 7 of Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens dataset January 2020
Additional file 8 of Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens dataset January 2020

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