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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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Related in: MedlinePlus

Alterations to seedling development in fln2–4 plants.(A) The phenotypes of WT and fln2–4 plant grown on 2% sucrose-containing MS medium for 7 days and 14 days. (B) The phenotypes of WT and fln2–4 plants grown in soil after growing on sucrose-containing medium for 14 days. Bars represent 1 cm. (C) Chloroplast ultrastructure in 7-day-old WT, 7-day-old fln2–4 plants, 14-day-old WT and 14-day-old fln2–4 plants. All of these plants grew on sucrose-containing medium. Scale bars: 1 µm. (D) The relative chlorophyll levels in WT and fln2–4 seedling during growth on sucrose-containing MS medium. The values presented are averages of three replicates ± SD.
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pone-0073092-g004: Alterations to seedling development in fln2–4 plants.(A) The phenotypes of WT and fln2–4 plant grown on 2% sucrose-containing MS medium for 7 days and 14 days. (B) The phenotypes of WT and fln2–4 plants grown in soil after growing on sucrose-containing medium for 14 days. Bars represent 1 cm. (C) Chloroplast ultrastructure in 7-day-old WT, 7-day-old fln2–4 plants, 14-day-old WT and 14-day-old fln2–4 plants. All of these plants grew on sucrose-containing medium. Scale bars: 1 µm. (D) The relative chlorophyll levels in WT and fln2–4 seedling during growth on sucrose-containing MS medium. The values presented are averages of three replicates ± SD.

Mentions: The delayed greening fln2–4 mutant exhibits sugar-dependent for the survival of seedlings and growth of green true leaves. When supplemented with sucrose, the 7-day-old fln2–4 seedlings displayed yellow-tinted cotyledons, and then developed greenish true leaves in two weeks after germination (Figure 4A). After transplanting them into soil, all the mutant seedlings with greenish true leaves could flower and produce fertile seeds without sucrose supplementation (Figure 4B). To unveil the ultrastructural basis of fln2–4 seedlings during the delayed greening process, we examined dynamic changes in chloroplasts using TEM. In the leaves of 7-day-old WT grown with sucrose, chloroplasts were crescent-shaped and contained well-formed internal membrane structures including stroma thylakoids and stacked grana thylakoids (Figure 4C). In contrast, at the same stage, the chloroplasts in the 7-day-old fln2–4 mutants were still highly vacuolated, but the lamellar membrane structures appeared (Figure 4C). In the 14-day-old fln2–4 mutants grown under the same conditions, chloroplasts with well-organized thylakoid membrane could be observed (Figure 4C). This suggests the fln2–4 chloroplast can be gradually formed although its development is slower than that in WT. In addition, we measured the levels of chlorophyll a and b in both the mutant and WT seedlings during the greening process. The total chlorophyll content of fln2–4 mutant (93.58±2.45 mg g−1 fresh weight for the fln2–4 mutant type) was about 16.9% of WT (554.94±15.51 mg g−1 fresh weight for the wild type) grown with sucrose for 7 days, and the chlorophyll a/b ratio of fln2–4 was about half of WT (Figure 4D; Table 1). In 14-day-old mutant seedlings grown under the same conditions, the chlorophyll content (292.16±24.91 mg g−1 fresh weight for the fln2–4 mutant type) was about 42% compared to that of the WT (695.19±24.14 mg g−1 fresh weight for the wild type), and the chlorophyll a/b ratio was close to that of WT (Figure 4D; Table 1). These observations indicated that the chlorophyll biosynthesis in fln2–4 was partially recovered. Furthermore, we investigated the plastid ultrastructure development of the WT and fln2–4 grown on sucrose-containing medium during de-etiolation. In the WT and fln2–4 seedlings grown in darkness for 5 days, the etioplasts contained a large prolamellar body (Figure 5, left panels). When etiolated seedlings were exposed to light for 6 hours, the prolamellar in WT developed into stromal lamellae (Figure 5, middle panels). In contrast, plastids in fln2–4 contained less stromal lamellae (Figure 5, middle panels). After de-etiolation for 24 hours, plastids in WT contained well-developed thylakoid membrane system and starch granules, while loose thylakoid lamellae and grana thylakoids were detected in fln2–4 (Figure 5, right panels). When grown on MS medium without sucrose in darkness for 5 days, the etioplasts of fln2–4 were similar with that of the WT. After de-etiolation for 24 hours, only a few thylakoid lamellae could be observed in fln2–4 (Figure 5). These results revealed that plastid development in fln2–4 grown on sucrose-containing medium proceeds slowly, but it can gradually form well-structured chloroplast during the de-etiolation process.


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)

Alterations to seedling development in fln2–4 plants.(A) The phenotypes of WT and fln2–4 plant grown on 2% sucrose-containing MS medium for 7 days and 14 days. (B) The phenotypes of WT and fln2–4 plants grown in soil after growing on sucrose-containing medium for 14 days. Bars represent 1 cm. (C) Chloroplast ultrastructure in 7-day-old WT, 7-day-old fln2–4 plants, 14-day-old WT and 14-day-old fln2–4 plants. All of these plants grew on sucrose-containing medium. Scale bars: 1 µm. (D) The relative chlorophyll levels in WT and fln2–4 seedling during growth on sucrose-containing MS medium. The values presented are averages of three replicates ± SD.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0073092-g004: Alterations to seedling development in fln2–4 plants.(A) The phenotypes of WT and fln2–4 plant grown on 2% sucrose-containing MS medium for 7 days and 14 days. (B) The phenotypes of WT and fln2–4 plants grown in soil after growing on sucrose-containing medium for 14 days. Bars represent 1 cm. (C) Chloroplast ultrastructure in 7-day-old WT, 7-day-old fln2–4 plants, 14-day-old WT and 14-day-old fln2–4 plants. All of these plants grew on sucrose-containing medium. Scale bars: 1 µm. (D) The relative chlorophyll levels in WT and fln2–4 seedling during growth on sucrose-containing MS medium. The values presented are averages of three replicates ± SD.
Mentions: The delayed greening fln2–4 mutant exhibits sugar-dependent for the survival of seedlings and growth of green true leaves. When supplemented with sucrose, the 7-day-old fln2–4 seedlings displayed yellow-tinted cotyledons, and then developed greenish true leaves in two weeks after germination (Figure 4A). After transplanting them into soil, all the mutant seedlings with greenish true leaves could flower and produce fertile seeds without sucrose supplementation (Figure 4B). To unveil the ultrastructural basis of fln2–4 seedlings during the delayed greening process, we examined dynamic changes in chloroplasts using TEM. In the leaves of 7-day-old WT grown with sucrose, chloroplasts were crescent-shaped and contained well-formed internal membrane structures including stroma thylakoids and stacked grana thylakoids (Figure 4C). In contrast, at the same stage, the chloroplasts in the 7-day-old fln2–4 mutants were still highly vacuolated, but the lamellar membrane structures appeared (Figure 4C). In the 14-day-old fln2–4 mutants grown under the same conditions, chloroplasts with well-organized thylakoid membrane could be observed (Figure 4C). This suggests the fln2–4 chloroplast can be gradually formed although its development is slower than that in WT. In addition, we measured the levels of chlorophyll a and b in both the mutant and WT seedlings during the greening process. The total chlorophyll content of fln2–4 mutant (93.58±2.45 mg g−1 fresh weight for the fln2–4 mutant type) was about 16.9% of WT (554.94±15.51 mg g−1 fresh weight for the wild type) grown with sucrose for 7 days, and the chlorophyll a/b ratio of fln2–4 was about half of WT (Figure 4D; Table 1). In 14-day-old mutant seedlings grown under the same conditions, the chlorophyll content (292.16±24.91 mg g−1 fresh weight for the fln2–4 mutant type) was about 42% compared to that of the WT (695.19±24.14 mg g−1 fresh weight for the wild type), and the chlorophyll a/b ratio was close to that of WT (Figure 4D; Table 1). These observations indicated that the chlorophyll biosynthesis in fln2–4 was partially recovered. Furthermore, we investigated the plastid ultrastructure development of the WT and fln2–4 grown on sucrose-containing medium during de-etiolation. In the WT and fln2–4 seedlings grown in darkness for 5 days, the etioplasts contained a large prolamellar body (Figure 5, left panels). When etiolated seedlings were exposed to light for 6 hours, the prolamellar in WT developed into stromal lamellae (Figure 5, middle panels). In contrast, plastids in fln2–4 contained less stromal lamellae (Figure 5, middle panels). After de-etiolation for 24 hours, plastids in WT contained well-developed thylakoid membrane system and starch granules, while loose thylakoid lamellae and grana thylakoids were detected in fln2–4 (Figure 5, right panels). When grown on MS medium without sucrose in darkness for 5 days, the etioplasts of fln2–4 were similar with that of the WT. After de-etiolation for 24 hours, only a few thylakoid lamellae could be observed in fln2–4 (Figure 5). These results revealed that plastid development in fln2–4 grown on sucrose-containing medium proceeds slowly, but it can gradually form well-structured chloroplast during the de-etiolation process.

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