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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

Immunoblot analysis of D1 accumulation in cysteine-mutant VKORs transgenic plants under growth light or in high light. Thylakoid membrane proteins were extracted from the leaves of AtVKORWT, vkor mutant and cysteine-mutant VKORs plants. The immunoblot was detected by D1-antibody. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.
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Figure 3: Immunoblot analysis of D1 accumulation in cysteine-mutant VKORs transgenic plants under growth light or in high light. Thylakoid membrane proteins were extracted from the leaves of AtVKORWT, vkor mutant and cysteine-mutant VKORs plants. The immunoblot was detected by D1-antibody. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.

Mentions: The turnover of D1 protein is one of photoprotective processes in PSII under high light stress (Nishiyama et al., 2001; Huesgen et al., 2006). Under normal growth light, the levels of D1 protein in transgenic plants with mutant AtVKORs of conservative cysteine were decreased, especially in double-cysteine mutants AtVKORC109AC116A and AtVKORC195AC198A (Figures 3 and 4). High irradiance increased the decrease extent of D1 protein, and only trace amount of D1 accumulation could be detected in the vkor mutant line and double-cysteine mutant plants, which is consistent with the previous result that the deficiency of AtVKOR accelerates the degradation of D1 protein (Yu et al., 2014). Little difference was observed in the level of D1 protein among the transgenic plants with mutant AtVKORs of non-conservative cysteine and AtVKORWT (Figures 3 and 4). The results above suggested that the turnover of D1 protein in the repair of photodamaged were impaired due to the mutations of conservative cysteine in the AtVKOR domain, which are directly related to its oxidoreductase activity.


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)

Immunoblot analysis of D1 accumulation in cysteine-mutant VKORs transgenic plants under growth light or in high light. Thylakoid membrane proteins were extracted from the leaves of AtVKORWT, vkor mutant and cysteine-mutant VKORs plants. The immunoblot was detected by D1-antibody. 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 3: Immunoblot analysis of D1 accumulation in cysteine-mutant VKORs transgenic plants under growth light or in high light. Thylakoid membrane proteins were extracted from the leaves of AtVKORWT, vkor mutant and cysteine-mutant VKORs plants. The immunoblot was detected by D1-antibody. Growth light: 120 μmol m-2 s-1; High light: 600 μmol m-2 s-1 for 2 h.
Mentions: The turnover of D1 protein is one of photoprotective processes in PSII under high light stress (Nishiyama et al., 2001; Huesgen et al., 2006). Under normal growth light, the levels of D1 protein in transgenic plants with mutant AtVKORs of conservative cysteine were decreased, especially in double-cysteine mutants AtVKORC109AC116A and AtVKORC195AC198A (Figures 3 and 4). High irradiance increased the decrease extent of D1 protein, and only trace amount of D1 accumulation could be detected in the vkor mutant line and double-cysteine mutant plants, which is consistent with the previous result that the deficiency of AtVKOR accelerates the degradation of D1 protein (Yu et al., 2014). Little difference was observed in the level of D1 protein among the transgenic plants with mutant AtVKORs of non-conservative cysteine and AtVKORWT (Figures 3 and 4). The results above suggested that the turnover of D1 protein in the repair of photodamaged were impaired due to the mutations of conservative cysteine in the AtVKOR domain, which are directly related to its oxidoreductase activity.

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