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The reduced plastid-encoded polymerase-dependent plastid gene expression leads to the delayed greening of the Arabidopsis fln2 mutant.

Huang C, Yu QB, Lv RH, Yin QQ, Chen GY, Xu L, Yang ZN - PLoS ONE (2013)

Bottom Line: This indicates that FLN2 functions in regulation of PEP activity associated with these TAC components. fln2-4 exhibited delayed greening on sucrose-containing medium.Together with the data that FLN1 could interact with itself in yeast, FLN1 may form a homodimer to replace FLN1-FLN2 as the TRX z target in redox pathway for maintaining partial PEP activity in fln2-4.We proposed the partial PEP activity in the fln2 mutant allowed plastids to develop into fully functional chloroplasts when exogenous sucrose was supplied, and finally the mutants exhibited green phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China ; Department of Biology, School of Life Sciences, East China Normal University, Shanghai, P.R. China.

ABSTRACT
In Arabidopsis leaf coloration mutants, the delayed greening phenomenon is common. Nonetheless, the mechanism remains largely elusive. Here, a delayed greening mutant fln2-4 of FLN2 (Fructokinase-Like Protein2) was studied. FLN2 is one component of Transcriptionally Active Chromosome (TAC) complex which is thought to contain the complete plastid-encoded polymerase (PEP). fln2-4 displayed albino phenotype on medium without sucrose. The PEP-dependent plastid gene expression and chloroplast development were inhibited in fln2-4. Besides interacting with thioredoxin z (TRX z), we identified that FLN2 interacted with another two members of TAC complex in yeast including its homologous protein FLN1 (Fructokinase-Like Protein1) and pTAC5. This indicates that FLN2 functions in regulation of PEP activity associated with these TAC components. fln2-4 exhibited delayed greening on sucrose-containing medium. Comparison of the PEP-dependent gene expression among two complete albino mutants (trx z and ptac14), two yellow mutants (ecb2-2 and ys1) and the fln2-4 showed that fln2-4 remains partial PEP activity. FLN2 and FLN1 are the target proteins of TRX z involved in affecting the PEP activity. Together with the data that FLN1 could interact with itself in yeast, FLN1 may form a homodimer to replace FLN1-FLN2 as the TRX z target in redox pathway for maintaining partial PEP activity in fln2-4. We proposed the partial PEP activity in the fln2 mutant allowed plastids to develop into fully functional chloroplasts when exogenous sucrose was supplied, and finally the mutants exhibited green phenotype.

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Expression analysis of the plastid encoded genes in fln2–4 seedlings.Northern blot was performed to detect the plastid gene transcript levels in the 7-day-old fln2–4 seedlings and WT grown on MS medium without sucrose. Three classes of genes were examined, psbA, psbB, and rbcL were selected as PEP-dependent genes, clpP and rrn16 were selected as PEP- and NEP-dependent genes, accD and rpoA were selected as NEP-dependent genes.
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pone-0073092-g002: Expression analysis of the plastid encoded genes in fln2–4 seedlings.Northern blot was performed to detect the plastid gene transcript levels in the 7-day-old fln2–4 seedlings and WT grown on MS medium without sucrose. Three classes of genes were examined, psbA, psbB, and rbcL were selected as PEP-dependent genes, clpP and rrn16 were selected as PEP- and NEP-dependent genes, accD and rpoA were selected as NEP-dependent genes.

Mentions: FLN2 is one component of TAC, and many TAC members were reported to affect the plastid gene expression [15]–[17], [20]–[22]. To investigate the effect of the knockout of the FLN2 gene on the plastid gene expression, we used Northern hybridization to examine the transcriptional levels of plastid genes in 7-day-old fln2–4 mutants grown on MS medium without sucrose. The plastid genes are categorized into three classes based on whether they are transcribed by PEP and/or NEP [36]. The class I and class III genes are exclusively transcribed by PEP and NEP, respectively. While the class II genes are both PEP- and NEP-dependent. Our results showed that the expression of the class I genes (psbA, psbB and rbcL) were strongly reduced in the fln2–4 mutant compared with that of the WT. By contrast, the transcript levels of the class-II genes (rrn16 and clpP) and the class-III genes (accD and rpoA) did not have any significant variation between fln2–4 mutant and WT (Figure 2). These results confirm that loss of FLN2 mainly affects the expression of PEP-dependent plastid genes.


The reduced plastid-encoded polymerase-dependent plastid gene expression leads to the delayed greening of the Arabidopsis fln2 mutant.

Huang C, Yu QB, Lv RH, Yin QQ, Chen GY, Xu L, Yang ZN - PLoS ONE (2013)

Expression analysis of the plastid encoded genes in fln2–4 seedlings.Northern blot was performed to detect the plastid gene transcript levels in the 7-day-old fln2–4 seedlings and WT grown on MS medium without sucrose. Three classes of genes were examined, psbA, psbB, and rbcL were selected as PEP-dependent genes, clpP and rrn16 were selected as PEP- and NEP-dependent genes, accD and rpoA were selected as NEP-dependent genes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3760890&req=5

pone-0073092-g002: Expression analysis of the plastid encoded genes in fln2–4 seedlings.Northern blot was performed to detect the plastid gene transcript levels in the 7-day-old fln2–4 seedlings and WT grown on MS medium without sucrose. Three classes of genes were examined, psbA, psbB, and rbcL were selected as PEP-dependent genes, clpP and rrn16 were selected as PEP- and NEP-dependent genes, accD and rpoA were selected as NEP-dependent genes.
Mentions: FLN2 is one component of TAC, and many TAC members were reported to affect the plastid gene expression [15]–[17], [20]–[22]. To investigate the effect of the knockout of the FLN2 gene on the plastid gene expression, we used Northern hybridization to examine the transcriptional levels of plastid genes in 7-day-old fln2–4 mutants grown on MS medium without sucrose. The plastid genes are categorized into three classes based on whether they are transcribed by PEP and/or NEP [36]. The class I and class III genes are exclusively transcribed by PEP and NEP, respectively. While the class II genes are both PEP- and NEP-dependent. Our results showed that the expression of the class I genes (psbA, psbB and rbcL) were strongly reduced in the fln2–4 mutant compared with that of the WT. By contrast, the transcript levels of the class-II genes (rrn16 and clpP) and the class-III genes (accD and rpoA) did not have any significant variation between fln2–4 mutant and WT (Figure 2). These results confirm that loss of FLN2 mainly affects the expression of PEP-dependent plastid genes.

Bottom Line: This indicates that FLN2 functions in regulation of PEP activity associated with these TAC components. fln2-4 exhibited delayed greening on sucrose-containing medium.Together with the data that FLN1 could interact with itself in yeast, FLN1 may form a homodimer to replace FLN1-FLN2 as the TRX z target in redox pathway for maintaining partial PEP activity in fln2-4.We proposed the partial PEP activity in the fln2 mutant allowed plastids to develop into fully functional chloroplasts when exogenous sucrose was supplied, and finally the mutants exhibited green phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, College of Life and Environmental Sciences, Shanghai Normal University, Shanghai, P.R. China ; Department of Biology, School of Life Sciences, East China Normal University, Shanghai, P.R. China.

ABSTRACT
In Arabidopsis leaf coloration mutants, the delayed greening phenomenon is common. Nonetheless, the mechanism remains largely elusive. Here, a delayed greening mutant fln2-4 of FLN2 (Fructokinase-Like Protein2) was studied. FLN2 is one component of Transcriptionally Active Chromosome (TAC) complex which is thought to contain the complete plastid-encoded polymerase (PEP). fln2-4 displayed albino phenotype on medium without sucrose. The PEP-dependent plastid gene expression and chloroplast development were inhibited in fln2-4. Besides interacting with thioredoxin z (TRX z), we identified that FLN2 interacted with another two members of TAC complex in yeast including its homologous protein FLN1 (Fructokinase-Like Protein1) and pTAC5. This indicates that FLN2 functions in regulation of PEP activity associated with these TAC components. fln2-4 exhibited delayed greening on sucrose-containing medium. Comparison of the PEP-dependent gene expression among two complete albino mutants (trx z and ptac14), two yellow mutants (ecb2-2 and ys1) and the fln2-4 showed that fln2-4 remains partial PEP activity. FLN2 and FLN1 are the target proteins of TRX z involved in affecting the PEP activity. Together with the data that FLN1 could interact with itself in yeast, FLN1 may form a homodimer to replace FLN1-FLN2 as the TRX z target in redox pathway for maintaining partial PEP activity in fln2-4. We proposed the partial PEP activity in the fln2 mutant allowed plastids to develop into fully functional chloroplasts when exogenous sucrose was supplied, and finally the mutants exhibited green phenotype.

Show MeSH
Related in: MedlinePlus