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The conservative cysteines in transmembrane domain of AtVKOR/LTO1 are critical for photosynthetic growth and photosystem II activity in Arabidopsis.

Du JJ, Zhan CY, Lu Y, Cui HR, Wang XY - Front Plant Sci (2015)

Bottom Line: Consistently, the maximum and actual efficiency of photosystem II (PSII) in double-cysteine mutation plants decreased significantly to the level similar to that of the vkor mutant line both under normal growth light and high light.A significantly decreased amount of D1 protein and increased accumulation of reactive oxygen species were observed in two double-cysteine mutations under high light.All of the results above indicated that the conservative cysteines in transmembrane domains were the functional sites of AtVKOR in Arabidopsis and that the oxidoreductase activities of AtVKOR were directly related to the autotrophic photosynthetic growth and PSII activity of Arabidopsis thaliana.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Biology, College of Life Science, Shandong Agricultural University Tai´an, China.

ABSTRACT
Thylakoid protein vitamin K epoxide reductase (AtVKOR/LTO1) is involved in oxidoreduction. The deficiency of this compound causes pleiotropic defects in Arabidopsis thaliana, such as severely stunted growth, smaller sized leaves, and delay of flowering. Transgenic complementation of wild-type AtVKOR (VKORWT) to vkor mutant lines ultimately demonstrates that the phenotype changes are due to this gene. However, whether AtVKOR functions in Arabidopsis through its protein oxidoreduction is unknown. To further study the redox-active sites of AtVKOR in vivo, a series of plasmids containing cysteine-mutant VKORs were constructed and transformed into vkor deficient lines. Compared with transgenic AtVKORWT plants, the size of the transgenic plants with a single conservative cysteine mutation (VKORC109A, VKORC116A, VKORC195A, and VKORC198A) were smaller, and two double-cysteine mutations (VKORC109AC116A and VKORC195AC198A) showed significantly stunted growth, similar with the vkor mutant line. However, mutations of two non-conservative cysteines (VKORC46A and VKORC230A) displayed little obvious changes in the phenotypes of Arabidopsis. Consistently, the maximum and actual efficiency of photosystem II (PSII) in double-cysteine mutation plants decreased significantly to the level similar to that of the vkor mutant line both under normal growth light and high light. A significantly decreased amount of D1 protein and increased accumulation of reactive oxygen species were observed in two double-cysteine mutations under high light. All of the results above indicated that the conservative cysteines in transmembrane domains were the functional sites of AtVKOR in Arabidopsis and that the oxidoreductase activities of AtVKOR were directly related to the autotrophic photosynthetic growth and PSII activity of Arabidopsis thaliana.

No MeSH data available.


Related in: MedlinePlus

Levels of H2O2 in cysteine-mutant VKORs transgenic plants under growth light or in high light. Quantitative accumulations of H2O2 were, respectively, detected in 6-weeks-old leaves from WT, vkor mutant, AtVKORWT, and cysteine-mutant VKORs plants under growth light or in high light. The error bars indicated the SD. Significant differences are determined using one-way ANOVA and Ducan’s Multiple Range Test, indicated with different letters at P < 0.05 significance level. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.
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Figure 5: Levels of H2O2 in cysteine-mutant VKORs transgenic plants under growth light or in high light. Quantitative accumulations of H2O2 were, respectively, detected in 6-weeks-old leaves from WT, vkor mutant, AtVKORWT, and cysteine-mutant VKORs plants under growth light or in high light. The error bars indicated the SD. Significant differences are determined using one-way ANOVA and Ducan’s Multiple Range Test, indicated with different letters at P < 0.05 significance level. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.

Mentions: In chloroplasts, the damage of PSII assembly is usually associated with the harmful production of ROS, such as H2O2, O2⋅-, and singlet oxygen (Cejkova et al., 1998; Murata et al., 2007). Previous studies show that much more H2O2 and O2⋅- are accumulated in the vkor mutant than in wild-type plants (Lu et al., 2013). By checking the levels of H2O2 and O2⋅- in transgenic plants, we found that the amounts of ROS in plants with mutations of conservative cysteine VKORs were higher than that of AtVKORWT plants under growth light (Figures 5 and 6). Under high irradiance, the elevated accumulations of H2O2 and O2⋅- in AtVKORC109AC116A and AtVKORC195AC198A plants were detected, similar to that of the vkor mutant line (Figures 5 and 6). As to the transgenic plants of AtVKORC46A, AtVKORC230A, the levels of H2O2 and O2⋅- were quite closed to that in AtVKORWT plants (Figures 5 and 6). The results further indicated that the photoprotection mechanism was damaged in the transgenic plants with mutant AtVKORs of conservative cysteine.


The conservative cysteines in transmembrane domain of AtVKOR/LTO1 are critical for photosynthetic growth and photosystem II activity in Arabidopsis.

Du JJ, Zhan CY, Lu Y, Cui HR, Wang XY - Front Plant Sci (2015)

Levels of H2O2 in cysteine-mutant VKORs transgenic plants under growth light or in high light. Quantitative accumulations of H2O2 were, respectively, detected in 6-weeks-old leaves from WT, vkor mutant, AtVKORWT, and cysteine-mutant VKORs plants under growth light or in high light. The error bars indicated the SD. Significant differences are determined using one-way ANOVA and Ducan’s Multiple Range Test, indicated with different letters at P < 0.05 significance level. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400859&req=5

Figure 5: Levels of H2O2 in cysteine-mutant VKORs transgenic plants under growth light or in high light. Quantitative accumulations of H2O2 were, respectively, detected in 6-weeks-old leaves from WT, vkor mutant, AtVKORWT, and cysteine-mutant VKORs plants under growth light or in high light. The error bars indicated the SD. Significant differences are determined using one-way ANOVA and Ducan’s Multiple Range Test, indicated with different letters at P < 0.05 significance level. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.
Mentions: In chloroplasts, the damage of PSII assembly is usually associated with the harmful production of ROS, such as H2O2, O2⋅-, and singlet oxygen (Cejkova et al., 1998; Murata et al., 2007). Previous studies show that much more H2O2 and O2⋅- are accumulated in the vkor mutant than in wild-type plants (Lu et al., 2013). By checking the levels of H2O2 and O2⋅- in transgenic plants, we found that the amounts of ROS in plants with mutations of conservative cysteine VKORs were higher than that of AtVKORWT plants under growth light (Figures 5 and 6). Under high irradiance, the elevated accumulations of H2O2 and O2⋅- in AtVKORC109AC116A and AtVKORC195AC198A plants were detected, similar to that of the vkor mutant line (Figures 5 and 6). As to the transgenic plants of AtVKORC46A, AtVKORC230A, the levels of H2O2 and O2⋅- were quite closed to that in AtVKORWT plants (Figures 5 and 6). The results further indicated that the photoprotection mechanism was damaged in the transgenic plants with mutant AtVKORs of conservative cysteine.

Bottom Line: Consistently, the maximum and actual efficiency of photosystem II (PSII) in double-cysteine mutation plants decreased significantly to the level similar to that of the vkor mutant line both under normal growth light and high light.A significantly decreased amount of D1 protein and increased accumulation of reactive oxygen species were observed in two double-cysteine mutations under high light.All of the results above indicated that the conservative cysteines in transmembrane domains were the functional sites of AtVKOR in Arabidopsis and that the oxidoreductase activities of AtVKOR were directly related to the autotrophic photosynthetic growth and PSII activity of Arabidopsis thaliana.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Biology, College of Life Science, Shandong Agricultural University Tai´an, China.

ABSTRACT
Thylakoid protein vitamin K epoxide reductase (AtVKOR/LTO1) is involved in oxidoreduction. The deficiency of this compound causes pleiotropic defects in Arabidopsis thaliana, such as severely stunted growth, smaller sized leaves, and delay of flowering. Transgenic complementation of wild-type AtVKOR (VKORWT) to vkor mutant lines ultimately demonstrates that the phenotype changes are due to this gene. However, whether AtVKOR functions in Arabidopsis through its protein oxidoreduction is unknown. To further study the redox-active sites of AtVKOR in vivo, a series of plasmids containing cysteine-mutant VKORs were constructed and transformed into vkor deficient lines. Compared with transgenic AtVKORWT plants, the size of the transgenic plants with a single conservative cysteine mutation (VKORC109A, VKORC116A, VKORC195A, and VKORC198A) were smaller, and two double-cysteine mutations (VKORC109AC116A and VKORC195AC198A) showed significantly stunted growth, similar with the vkor mutant line. However, mutations of two non-conservative cysteines (VKORC46A and VKORC230A) displayed little obvious changes in the phenotypes of Arabidopsis. Consistently, the maximum and actual efficiency of photosystem II (PSII) in double-cysteine mutation plants decreased significantly to the level similar to that of the vkor mutant line both under normal growth light and high light. A significantly decreased amount of D1 protein and increased accumulation of reactive oxygen species were observed in two double-cysteine mutations under high light. All of the results above indicated that the conservative cysteines in transmembrane domains were the functional sites of AtVKOR in Arabidopsis and that the oxidoreductase activities of AtVKOR were directly related to the autotrophic photosynthetic growth and PSII activity of Arabidopsis thaliana.

No MeSH data available.


Related in: MedlinePlus