Arabidopsis Variegation Mutants

Rodermel, Steven R.

doi:10.1199/tab.0079

Cited by 36 publications

(64 citation statements)

References 139 publications

(258 reference statements)

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“…Variegation mutants are powerful tools to gain insight into mechanisms of chloroplast biogenesis (Sakamoto et al, 2003; for review, see Rodermel, 2002;Yu et al, 2007). The Arabidopsis (Arabidopsis thaliana) yellow variegated2 (var2) mutant has green cotyledons but its true leaves are green and white sectored; sectoring is produced in homozygous recessive plants.…”

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confidence: 99%

An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis

2010

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The Arabidopsis (Arabidopsis thaliana) yellow variegated2 (var2) mutant has green-and white-sectored leaves due to loss of VAR2, a subunit of the chloroplast FtsH protease/chaperone complex. Suppressor screens are a valuable tool to gain insight into VAR2 function and the mechanism of var2 variegation. Here, we report the molecular characterization of 004-003, a line in which var2 variegation is suppressed. We found that the suppression phenotype in this line is caused by lack of a chloroplast pentatricopeptide repeat (PPR) protein that we named SUPPRESSOR OF VARIEGATION7 (SVR7). PPR proteins contain tandemly repeated PPR motifs that bind specific RNAs, and they are thought to be central regulators of chloroplast and mitochondrial nucleic acid metabolism in plants. The svr7 mutant has defects in chloroplast ribosomal RNA (rRNA) processing that are different from those in other svr mutants, and these defects are correlated with reductions in the accumulation of some chloroplast proteins, directly or indirectly. We also found that whereas var2 displays a leaf variegation phenotype at 22°C, it has a pronounced chlorosis phenotype at 8°C that is correlated with defects in chloroplast rRNA processing and a drastic reduction in chloroplast protein accumulation. Surprisingly, the cold-induced phenotype of var2 cannot be suppressed by svr7. Our results strengthen the previously established linkage between var2 variegation and chloroplast rRNA processing/chloroplast translation, and they also point toward the possibility that VAR2 mediates different activities in chloroplast biogenesis at normal and chilling temperatures.

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An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis

2010

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“…The variegated phenotype is characterized by distinct green and white sectored leaves (Rodermel, 2001(Rodermel, , 2002Miura et al, 2007). The green sectors contain normal chloroplasts, whereas the white sectors contain plastids devoid of chlorophyll and/or carotenoids (Rodermel, 2002;Miura et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

“…The green sectors contain normal chloroplasts, whereas the white sectors contain plastids devoid of chlorophyll and/or carotenoids (Rodermel, 2002;Miura et al, 2007). Variegated plants include the immutans (im) mutant of Arabidopsis, which was isolated and preliminarily characterized nearly 50 years ago (Ré dei, 1963(Ré dei, , 1975Rö bbelen, 1968).…”

Section: Introductionmentioning

confidence: 99%

Photosynthetic Redox Imbalance Governs Leaf Sectoring in theArabidopsis thalianaVariegation Mutantsimmutans,spotty,var1, andvar2

et al. 2009

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We hypothesized that chloroplast energy imbalance sensed through alterations in the redox state of the photosynthetic electron transport chain, measured as excitation pressure, governs the extent of variegation in the immutans mutant of Arabidopsis thaliana. To test this hypothesis, we developed a nondestructive imaging technique and used it to quantify the extent of variegation in vivo as a function of growth temperature and irradiance. The extent of variegation was positively correlated (R 2 = 0.750) with an increase in excitation pressure irrespective of whether high light, low temperature, or continuous illumination was used to induce increased excitation pressure. Similar trends were observed with the variegated mutants spotty, var1, and var2. Measurements of greening of etiolated wild-type and immutans cotyledons indicated that the absence of IMMUTANS increased excitation pressure twofold during the first 6 to 12 h of greening, which led to impaired biogenesis of thylakoid membranes. In contrast with IMMUTANS, the expression of its mitochondrial analog, AOX1a, was transiently upregulated in the wild type but permanently upregulated in immutans, indicating that the effects of excitation pressure during greening were also detectable in mitochondria. We conclude that mutations involving components of the photosynthetic electron transport chain, such as those present in immutans, spotty, var1, and var2, predispose Arabidopsis chloroplasts to photooxidation under high excitation pressure, resulting in the variegated phenotype.

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“…Variegation mutants are ideal models to gain insight into the mechanisms of chloroplast biogenesis (reviewed in Rodermel, 2002;Sakamoto, 2003;Yu et al, 2007). A growing number of variegation mutants have been characterized at the molecular level, primarily in Arabidopsis thaliana, maize (Zea mays), and tomato (Solanum lycopersicum) (reviewed in Yu et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Mutations in SUPPRESSOR OF VARIEGATION1, a Factor Required for Normal Chloroplast Translation, Suppress var2-Mediated Leaf Variegation in Arabidopsis

et al. 2008

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The Arabidopsis thaliana yellow variegated2 (var2) mutant is variegated due to lack of a chloroplast FtsH-like metalloprotease (FtsH2/VAR2). We have generated suppressors of var2 variegation to gain insight into factors and pathways that interact with VAR2 during chloroplast biogenesis. Here, we describe two such suppressors. Suppression of variegation in the first line, TAG-FN, was caused by disruption of the nuclear gene (SUPPRESSOR OF VARIEGATION1 [SVR1]) for a chloroplast-localized homolog of pseudouridine (C) synthase, which isomerizes uridine to C in noncoding RNAs. svr1 single mutants were epistatic to var2, and they displayed a phenotypic syndrome that included defects in chloroplast rRNA processing, reduced chloroplast translation, reduced chloroplast protein accumulation, and elevated chloroplast mRNA levels. In the second line (TAG-IE), suppression of variegation was caused by a lesion in SVR2, the gene for the ClpR1 subunit of the chloroplast ClpP/R protease. Like svr1, svr2 was epistatic to var2, and clpR1 mutants had a phenotype that resembled svr1. We propose that an impairment of chloroplast translation in TAG-FN and TAG-IE decreased the demand for VAR2 activity during chloroplast biogenesis and that this resulted in the suppression of var2 variegation. Consistent with this hypothesis, var2 variegation was repressed by chemical inhibitors of chloroplast translation. In planta mutagenesis revealed that SVR1 not only played a role in uridine isomerization but that its physical presence was necessary for proper chloroplast rRNA processing. Our data indicate that defects in chloroplast rRNA processing are a common, but not universal, molecular phenotype associated with suppression of var2 variegation.

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Arabidopsis Variegation Mutants

Cited by 36 publications

References 139 publications

An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis

An Arabidopsis Pentatricopeptide Repeat Protein, SUPPRESSOR OF VARIEGATION7, Is Required for FtsH-Mediated Chloroplast Biogenesis

Photosynthetic Redox Imbalance Governs Leaf Sectoring in theArabidopsis thalianaVariegation Mutantsimmutans,spotty,var1, andvar2

Mutations in SUPPRESSOR OF VARIEGATION1, a Factor Required for Normal Chloroplast Translation, Suppress var2-Mediated Leaf Variegation in Arabidopsis

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