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Retrograde signaling from functionally heterogeneous plastids.

Lepistö A, Toivola J, Nikkanen L, Rintamäki E - Front Plant Sci (2012)

Bottom Line: We have previously demonstrated that the knockout of the chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) leads to a heterogeneous population of chloroplasts with a range of different functional states.Thus, the signals derived from anomalous chloroplasts repress expression of PhaNGs as well as genes associated with light receptor signaling and differentiation of stomata, implying interaction between retrograde pathways and plant development.Analysis of the nuclear gene expression in mutants of retrograde signaling pathways in ntrc background would reveal the components that mediate signals generated from heterogeneous plastids to nucleus.

View Article: PubMed Central - PubMed

Affiliation: Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku Turku, Finland.

ABSTRACT
Structural and functional components of chloroplast are encoded by genes localized both to nuclear and plastid genomes of plant cell. Development from etioplasts to chloroplasts is triggered by light receptors that activate the expression of photosynthesis-associated nuclear genes (PhaNGs). In addition to photoreceptor-mediated pathways, retrograde signals from the chloroplast to the nucleus activate or repress the expression of nuclear genes involved in acclimatory or stress responses in plant leaves. A plant mesophyll cell contains up to 100 chloroplasts that function autonomously, raising intriguing questions about homogeneity and coordination of retrograde signals transmitted from chloroplast to nucleus. We have previously demonstrated that the knockout of the chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) leads to a heterogeneous population of chloroplasts with a range of different functional states. The heterogeneous chloroplast population activates both redox-dependent and undifferentiated plastid-generated retrograde signaling pathways in the mutant leaves. Transcriptome data from the ntrc knockout lines suggest that the induction of the redox-dependent signaling pathway depends on light conditions and leads to activation of stress-responsive gene expression. Analysis of mutants in different developmental stages allows to dissect signals from normal and anomalous chloroplasts. Thus, the signals derived from anomalous chloroplasts repress expression of PhaNGs as well as genes associated with light receptor signaling and differentiation of stomata, implying interaction between retrograde pathways and plant development. Analysis of the nuclear gene expression in mutants of retrograde signaling pathways in ntrc background would reveal the components that mediate signals generated from heterogeneous plastids to nucleus.

No MeSH data available.


Related in: MedlinePlus

Rosette phenotypes, bright field images, and electron micrographs of the mesophyll cells in wild-type and ntrc line. The plants were grown under short (SD) and long (LD) photoperiod of 8 h and 16 h light, respectively. Plastid-like organelles with poorly developed thylakoid membranes are indicated by arrows. Scale bars: 20 μm in light microscope images and 2 μm in electron micrographs, respectively.
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Figure 1: Rosette phenotypes, bright field images, and electron micrographs of the mesophyll cells in wild-type and ntrc line. The plants were grown under short (SD) and long (LD) photoperiod of 8 h and 16 h light, respectively. Plastid-like organelles with poorly developed thylakoid membranes are indicated by arrows. Scale bars: 20 μm in light microscope images and 2 μm in electron micrographs, respectively.

Mentions: We have employed an Arabidopsis mutant lacking the nuclear-encoded chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) to dissect chloroplast retrograde signaling pathway. NTRC is a member of chloroplast thioredoxin family (Serrato et al., 2004). Redox-active cysteines in thioredoxins are used to reduce disulfide bridges in target proteins. NTRC knockout mutants (ntrc) have reduced growth and decreased chlorophyll content (Perez-Ruiz et al., 2006; Lepistö et al., 2009), indicating that it is an important component of the chloroplast redox network. NTRC has been shown to regulate the activities of chloroplast proteins involved in ROS scavenging, and in the synthesis of chlorophyll, starch, and aromatic amino acids (Perez-Ruiz et al., 2006; Stenbaek et al., 2008; Kirchsteiger et al., 2009; Lepistö et al., 2009; Michalska et al., 2009; Pulido et al., 2010). Intriguingly, ntrc mutants possess both normal chloroplasts and irregularly differentiated plastids in a single mesophyll cell (Figure 1; Lepistö and Rintamäki, 2012). Some of the chloroplasts in ntrc are elongated and possess anomalous terminal appendages (Lepistö, 2011). The mesophyll cells of ntrc lines also contain small plastid-like organelles with poorly developed thylakoid membranes (Figure 1; Lepistö and Rintamäki, 2012), suggesting that NTRC controls early steps of chloroplast differentiation.


Retrograde signaling from functionally heterogeneous plastids.

Lepistö A, Toivola J, Nikkanen L, Rintamäki E - Front Plant Sci (2012)

Rosette phenotypes, bright field images, and electron micrographs of the mesophyll cells in wild-type and ntrc line. The plants were grown under short (SD) and long (LD) photoperiod of 8 h and 16 h light, respectively. Plastid-like organelles with poorly developed thylakoid membranes are indicated by arrows. Scale bars: 20 μm in light microscope images and 2 μm in electron micrographs, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3526119&req=5

Figure 1: Rosette phenotypes, bright field images, and electron micrographs of the mesophyll cells in wild-type and ntrc line. The plants were grown under short (SD) and long (LD) photoperiod of 8 h and 16 h light, respectively. Plastid-like organelles with poorly developed thylakoid membranes are indicated by arrows. Scale bars: 20 μm in light microscope images and 2 μm in electron micrographs, respectively.
Mentions: We have employed an Arabidopsis mutant lacking the nuclear-encoded chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) to dissect chloroplast retrograde signaling pathway. NTRC is a member of chloroplast thioredoxin family (Serrato et al., 2004). Redox-active cysteines in thioredoxins are used to reduce disulfide bridges in target proteins. NTRC knockout mutants (ntrc) have reduced growth and decreased chlorophyll content (Perez-Ruiz et al., 2006; Lepistö et al., 2009), indicating that it is an important component of the chloroplast redox network. NTRC has been shown to regulate the activities of chloroplast proteins involved in ROS scavenging, and in the synthesis of chlorophyll, starch, and aromatic amino acids (Perez-Ruiz et al., 2006; Stenbaek et al., 2008; Kirchsteiger et al., 2009; Lepistö et al., 2009; Michalska et al., 2009; Pulido et al., 2010). Intriguingly, ntrc mutants possess both normal chloroplasts and irregularly differentiated plastids in a single mesophyll cell (Figure 1; Lepistö and Rintamäki, 2012). Some of the chloroplasts in ntrc are elongated and possess anomalous terminal appendages (Lepistö, 2011). The mesophyll cells of ntrc lines also contain small plastid-like organelles with poorly developed thylakoid membranes (Figure 1; Lepistö and Rintamäki, 2012), suggesting that NTRC controls early steps of chloroplast differentiation.

Bottom Line: We have previously demonstrated that the knockout of the chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) leads to a heterogeneous population of chloroplasts with a range of different functional states.Thus, the signals derived from anomalous chloroplasts repress expression of PhaNGs as well as genes associated with light receptor signaling and differentiation of stomata, implying interaction between retrograde pathways and plant development.Analysis of the nuclear gene expression in mutants of retrograde signaling pathways in ntrc background would reveal the components that mediate signals generated from heterogeneous plastids to nucleus.

View Article: PubMed Central - PubMed

Affiliation: Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku Turku, Finland.

ABSTRACT
Structural and functional components of chloroplast are encoded by genes localized both to nuclear and plastid genomes of plant cell. Development from etioplasts to chloroplasts is triggered by light receptors that activate the expression of photosynthesis-associated nuclear genes (PhaNGs). In addition to photoreceptor-mediated pathways, retrograde signals from the chloroplast to the nucleus activate or repress the expression of nuclear genes involved in acclimatory or stress responses in plant leaves. A plant mesophyll cell contains up to 100 chloroplasts that function autonomously, raising intriguing questions about homogeneity and coordination of retrograde signals transmitted from chloroplast to nucleus. We have previously demonstrated that the knockout of the chloroplast regulatory protein, chloroplast NADPH-dependent thioredoxin reductase (NTRC) leads to a heterogeneous population of chloroplasts with a range of different functional states. The heterogeneous chloroplast population activates both redox-dependent and undifferentiated plastid-generated retrograde signaling pathways in the mutant leaves. Transcriptome data from the ntrc knockout lines suggest that the induction of the redox-dependent signaling pathway depends on light conditions and leads to activation of stress-responsive gene expression. Analysis of mutants in different developmental stages allows to dissect signals from normal and anomalous chloroplasts. Thus, the signals derived from anomalous chloroplasts repress expression of PhaNGs as well as genes associated with light receptor signaling and differentiation of stomata, implying interaction between retrograde pathways and plant development. Analysis of the nuclear gene expression in mutants of retrograde signaling pathways in ntrc background would reveal the components that mediate signals generated from heterogeneous plastids to nucleus.

No MeSH data available.


Related in: MedlinePlus