Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development

Loschelder, Heike; Schweer, Jennifer; Link, Brigitte; Link, Gerhard

doi:10.1104/pp.106.085878

Cited by 66 publications

(82 citation statements)

References 48 publications

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“…NEP promoters are more active in the youngest, nongreen tissues early in leaf development, while PEP increases its activity during the maturation of chloroplasts (Allison et al, 1996;Hajdukiewicz et al, 1997). The complexity of promoter specificity and chloroplast transcription initiated by PEP is further increased by multiple nucleus-encoded s factors, whose expression is spatially and temporally regulated by environmental cues (Hess and Börner, 1999;Allison, 2000;Shiina et al, 2005;Loschelder et al, 2006). There are six chloroplast s factors (SIG1-SIG6) in Arabidopsis (Arabidopsis thaliana).…”

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confidence: 99%

A Functional Component of the Transcriptionally Active Chromosome Complex, Arabidopsis pTAC14, Interacts with pTAC12/HEMERA and Regulates Plastid Gene Expression

et al. 2011

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The SET domain-containing protein, pTAC14, was previously identified as a component of the transcriptionally active chromosome (TAC) complexes. Here, we investigated the function of pTAC14 in the regulation of plastid-encoded bacterialtype RNA polymerase (PEP) activity and chloroplast development. The knockout of pTAC14 led to the blockage of thylakoid formation in Arabidopsis (Arabidopsis thaliana), and ptac14 was seedling lethal. Sequence and transcriptional analysis showed that pTAC14 encodes a specific protein in plants that is located in the chloroplast associated with the thylakoid and that its expression depends on light. In addition, the transcript levels of all investigated PEP-dependent genes were clearly reduced in the ptac14-1 mutants, while the accumulation of nucleus-encoded phage-type RNA polymerase-dependent transcripts was increased, indicating an important role of pTAC14 in maintaining PEP activity. pTAC14 was found to interact with pTAC12/ HEMERA, another component of TACs that is involved in phytochrome signaling. The data suggest that pTAC14 is essential for proper chloroplast development, most likely by affecting PEP activity and regulating PEP-dependent plastid gene transcription in Arabidopsis together with pTAC12.

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A Functional Component of the Transcriptionally Active Chromosome Complex, Arabidopsis pTAC14, Interacts with pTAC12/HEMERA and Regulates Plastid Gene Expression

et al. 2011

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“…The Arabidopsis genome encodes six plastidlocalized s-factors (SIGs; SIG1-SIG6) that are clustered into the same superfamily of s 70 and implement the same function as those in bacteria (Gruber and Gross, 2003;Lysenko, 2007). Physiological and genetic evidence revealed that different s-factors function redundantly and specifically to regulate plastid gene expression in Arabidopsis (Kanamaru et al, 2001;Privat et al, 2003;Yao et al, 2003;Nagashima et al, 2004;Tsunoyama et al, 2004;Favory et al, 2005;Ishizaki et al, 2005;Loschelder et al, 2006;Zghidi et al, 2007). For example, loss of function of SIG2 or SIG6 resulted in slow chloroplast development because of inhibition of plastid gene expression, and the sig2 sig6 double mutant showed a very severe defect in chloroplast development and was unable to grow in nature (Shirano et al, 2000;Hanaoka et al, 2003;Ishizaki et al, 2005;Woodson et al, 2012).…”

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Leaf Variegation of Thylakoid Formation1 Is Suppressed by Mutations of Specific σ-Factors in Arabidopsis

Zhu

et al. 2015

Plant Physiol.

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Thylakoid Formation1 (THF1) has been shown to play roles in chloroplast development, resistance to excessive light, and chlorophyll degradation in Arabidopsis (Arabidopsis thaliana). To elucidate mechanisms underlying THF1-regulated chloroplast development, we mutagenized thf1 seeds with ethyl methanesulfonate and screened second-site recessive mutations that suppress its leaf variegation phenotype. Here, we characterized a unique suppressor line, 42-6, which displays a leaf virescent phenotype. Map-based cloning and genetic complementation results showed that thf1 variegation was suppressed by a mutation in s-FACTOR6 (SIG6), which is a plastid transcription factor specifically controlling gene expression through the plastid-encoded RNA polymerase. Northern-blot analysis revealed that plastid gene expression was down-regulated in not only 42-6 and sig6 but also, thf1 at the early stage of chloroplast development. Interestingly, mutations in SIG2 but not in other s-factors also suppressed thf1 leaf variegation. Furthermore, we found that leaf variegation of thf1 and var2 could be suppressed by several virescent mutations, including yellow seedling1, brz-insensitive-pale green2, and nitric oxide-associated protein1, indicating that virescent mutations suppress leaf variegation. Taken together, our results provide unique insights into thf1-mediated leaf variegation, which might be triggered by defects in plastid gene transcription.

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“…This gene is transcribed by the plastid-encoded plastid RNA polymerase (PEP) which functions in the expression of the other genes related to photosynthesis. The specificity for target genes and the spatial-temporal regulation of PEP-mediated transcription are regulated by nuclear-encoded sigma-like transcription factors (SIGs) (Isono et al 1997;Kanamaru and Tanaka 2004;Tsunoyama et al 2004;Favory et al 2005;Loschelder et al 2006;Tozawa et al 2007;Zghidi et al 2007). AtSIG6, which is one of the six SIGs identified in Arabidopsis, is involved in rbcL gene expression during the early developmental stage when the biosynthesis of RuBisCO is most active (Ishigaki et al 2005).…”

Section: Gene Expression Of Nuclear-and Chloroplast-encoded Subunits mentioning

confidence: 99%

Molecular mechanisms of RuBisCO biosynthesis in higher plants

Nishimura

Ogawa

Ashida

et al. 2008

Plant Biotechnology

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RuBisCO is a key enzyme catalyzing the CO 2 -fixing reaction in the initial step of the Calvin cycle. However, its enzymatic properties are inadequate for plants because of its small turnover rate of the carboxylase reaction (Harris and Koniger 1997) and its low affinity for CO 2 . Thus, this enzyme limits the rate of carbon assimilation and net photosynthesis (Yokota and Shigeoka 2007). To compensate for its enzymatic inefficiencies, RuBisCO comprises as much as half of leaf total soluble proteins in higher plants, corresponding to 30% of total nitrogen compounds in the leaves. Consequently RuBisCO is regarded as the most abundant protein in the world (Gatenby and Ellis 1990;Makino et al. 2003). Indeed, a decrease in the amount of RuBisCO causes strong inhibition of CO 2 assimilation and subsequent growth retardation (Rodermel et al. 1988;Quick et al. 1991;Hudson et al. 1992;Masle et al. 1993). Therefore, it is important to understand how plants synthesize RuBisCO abundantly and maintain a sufficient amount for growth and development. How is RuBisCO synthesized optimally in plant chloroplasts? Gene expression of nuclear-and chloroplast-encoded subunits of RuBisCORuBisCO functions as an enzyme in the chloroplast stroma with a hexadecameric structure consisting of eight large (LSU) and eight small subunits (SSU). LSUs and SSUs are synthesized through distinct processes as the genes encoding them are individually located on different genomes (Figure 1). SSU is encoded by rbcS in the nuclear genome as a multigene family ranging from 2 to 12 members (Gutteridge and Gatenby 1995). The expression of rbcS is regulated by various endogenous and/or exogenous signals, such as light/dark transition, light quality, circadian rhythm, temperature, atmospheric CO 2 concentration, and nitrogen supply. It is also controlled in an organ-and tissue-specific manner, and by developmental stages (Sugita and Gruissem 1987; Dedondar et al. 1993; Pilgrim and McClung 1993;Gesch et al. 1998;Yoon et al. 2001;Imai et al. 2007). The relationship between rbcS expression and light conditions has been studied well. The signal transduction pathway mediated by phytochrome and the G protein is involved in light-stimulated transcription and light quality-dependent expression pattern of rbcS (Zhou 1999). Dark-induced down-regulation of rbcS expression is regulated by CONSTITUTIVELY MORPHOGENIC/ DE-ETHIOLATED/FUSCA (COP/DET/FUS), which are well known as repressors of photomorphogenesis (Millar et al. 1994). However, cis elements or trans-acting factors involved in the regulation of the rbcS expression response to various endogenous and/or exogenous signals are not well understood.After transcription in the nucleus, rbcS mRNA is translated on 80S ribosomes in the cytosol to synthesize the precursor protein of SSU (PreSSU) with the transit peptide in its N-terminal required for targeting to the chloroplast. The PreSSU is carried to the chloroplast outer membrane by heat shock protein70 (hsp70) and 14- Molecular mechanisms of RuBisCO biosynthesis in hi...

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Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development

Cited by 66 publications

References 48 publications

A Functional Component of the Transcriptionally Active Chromosome Complex, Arabidopsis pTAC14, Interacts with pTAC12/HEMERA and Regulates Plastid Gene Expression

A Functional Component of the Transcriptionally Active Chromosome Complex, Arabidopsis pTAC14, Interacts with pTAC12/HEMERA and Regulates Plastid Gene Expression

Leaf Variegation of Thylakoid Formation1 Is Suppressed by Mutations of Specific σ-Factors in Arabidopsis

Molecular mechanisms of RuBisCO biosynthesis in higher plants

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