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Overexpression of protochlorophyllide oxidoreductase C regulates oxidative stress in Arabidopsis.

Pattanayak GK, Tripathy BC - PLoS ONE (2011)

Bottom Line: Further, PORCx plants treated with 5-aminolevulinicacid when exposed to light, photo-converted over-accumulated protochlorophyllide to chlorophyllide, reduced the generation of (1)O(2) and malonedialdehyde production and reduced plasma membrane damage.Reduced protochlorophyllide content in PORCx plants released the protochlorophyllide-mediated feed-back inhibition of 5-aminolevulinicacid biosynthesis that resulted in higher 5-aminolevulinicacid production.Increase of 5-aminolevulinicacid synthesis upregulated the gene and protein expression of several downstream chlorophyll biosynthetic enzymes elucidating a regulatory net work of expression of genes involved in 5-aminolevulinicacid and tetrapyrrole biosynthesis.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delphi, India.

ABSTRACT
Light absorbed by colored intermediates of chlorophyll biosynthesis is not utilized in photosynthesis; instead, it is transferred to molecular oxygen, generating singlet oxygen ((1)O(2)). As there is no enzymatic detoxification mechanism available in plants to destroy (1)O(2), its generation should be minimized. We manipulated the concentration of a major chlorophyll biosynthetic intermediate i.e., protochlorophyllide in Arabidopsis by overexpressing the light-inducible protochlorophyllide oxidoreductase C (PORC) that effectively phototransforms endogenous protochlorophyllide to chlorophyllide leading to minimal accumulation of the photosensitizer protochlorophyllide in light-grown plants. In PORC overexpressing (PORCx) plants exposed to high-light, the (1)O(2) generation and consequent malonedialdehyde production was minimal and the maximum quantum efficiency of photosystem II remained unaffected demonstrating that their photosynthetic apparatus and cellular organization were intact. Further, PORCx plants treated with 5-aminolevulinicacid when exposed to light, photo-converted over-accumulated protochlorophyllide to chlorophyllide, reduced the generation of (1)O(2) and malonedialdehyde production and reduced plasma membrane damage. So PORCx plants survived and bolted whereas, the 5-aminolevulinicacid-treated wild-type plants perished. Thus, overexpression of PORC could be biotechnologically exploited in crop plants for tolerance to (1)O(2)-induced oxidative stress, paving the use of 5-aminolevulinicacid as a selective commercial light-activated biodegradable herbicide. Reduced protochlorophyllide content in PORCx plants released the protochlorophyllide-mediated feed-back inhibition of 5-aminolevulinicacid biosynthesis that resulted in higher 5-aminolevulinicacid production. Increase of 5-aminolevulinicacid synthesis upregulated the gene and protein expression of several downstream chlorophyll biosynthetic enzymes elucidating a regulatory net work of expression of genes involved in 5-aminolevulinicacid and tetrapyrrole biosynthesis.

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PORCx plants are tolerant to ALA-inducd oxidative damage.WT and PORCx (T-13) plants were treated with ALA and exposed to light for different time periods. (A) Photographs of T-13 plants under ALA-induced oxidative damage. Notice the death of the WT plants after 24 h of light exposure, whereas T-13 plants are slightly damaged. (B) Survival of light-exposed T-13 plants treated with different concentration of ALA. Both WT and T-13 plants grown under the same condition as described above were treated with different concentration of ALA (from 1 mM to 5 mM) and their dose dependent tolerance was observed. Notice the WT plants were killed by 3 mM or 5 mM ALA-treatment.
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pone-0026532-g006: PORCx plants are tolerant to ALA-inducd oxidative damage.WT and PORCx (T-13) plants were treated with ALA and exposed to light for different time periods. (A) Photographs of T-13 plants under ALA-induced oxidative damage. Notice the death of the WT plants after 24 h of light exposure, whereas T-13 plants are slightly damaged. (B) Survival of light-exposed T-13 plants treated with different concentration of ALA. Both WT and T-13 plants grown under the same condition as described above were treated with different concentration of ALA (from 1 mM to 5 mM) and their dose dependent tolerance was observed. Notice the WT plants were killed by 3 mM or 5 mM ALA-treatment.

Mentions: To study the tolerance of PORCx plants to ALA-induced oxidative damage, WT and T-13 plants were sprayed with 3 mM ALA, kept in dark for 14 h and then exposed to light (100 µmoles photons m−2 s−1) for different time periods. The leaves of ALA-treated WT plants started wilting after 2 h of light exposure and they were severely damaged after 6–12 h of illumination (Figure 6A). After 24 h of continuous light exposure WT plants were completely bleached. Under identical conditions PORCx plants were tolerant to the 1O2-induced oxidative stress (Figure 6A).


Overexpression of protochlorophyllide oxidoreductase C regulates oxidative stress in Arabidopsis.

Pattanayak GK, Tripathy BC - PLoS ONE (2011)

PORCx plants are tolerant to ALA-inducd oxidative damage.WT and PORCx (T-13) plants were treated with ALA and exposed to light for different time periods. (A) Photographs of T-13 plants under ALA-induced oxidative damage. Notice the death of the WT plants after 24 h of light exposure, whereas T-13 plants are slightly damaged. (B) Survival of light-exposed T-13 plants treated with different concentration of ALA. Both WT and T-13 plants grown under the same condition as described above were treated with different concentration of ALA (from 1 mM to 5 mM) and their dose dependent tolerance was observed. Notice the WT plants were killed by 3 mM or 5 mM ALA-treatment.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198771&req=5

pone-0026532-g006: PORCx plants are tolerant to ALA-inducd oxidative damage.WT and PORCx (T-13) plants were treated with ALA and exposed to light for different time periods. (A) Photographs of T-13 plants under ALA-induced oxidative damage. Notice the death of the WT plants after 24 h of light exposure, whereas T-13 plants are slightly damaged. (B) Survival of light-exposed T-13 plants treated with different concentration of ALA. Both WT and T-13 plants grown under the same condition as described above were treated with different concentration of ALA (from 1 mM to 5 mM) and their dose dependent tolerance was observed. Notice the WT plants were killed by 3 mM or 5 mM ALA-treatment.
Mentions: To study the tolerance of PORCx plants to ALA-induced oxidative damage, WT and T-13 plants were sprayed with 3 mM ALA, kept in dark for 14 h and then exposed to light (100 µmoles photons m−2 s−1) for different time periods. The leaves of ALA-treated WT plants started wilting after 2 h of light exposure and they were severely damaged after 6–12 h of illumination (Figure 6A). After 24 h of continuous light exposure WT plants were completely bleached. Under identical conditions PORCx plants were tolerant to the 1O2-induced oxidative stress (Figure 6A).

Bottom Line: Further, PORCx plants treated with 5-aminolevulinicacid when exposed to light, photo-converted over-accumulated protochlorophyllide to chlorophyllide, reduced the generation of (1)O(2) and malonedialdehyde production and reduced plasma membrane damage.Reduced protochlorophyllide content in PORCx plants released the protochlorophyllide-mediated feed-back inhibition of 5-aminolevulinicacid biosynthesis that resulted in higher 5-aminolevulinicacid production.Increase of 5-aminolevulinicacid synthesis upregulated the gene and protein expression of several downstream chlorophyll biosynthetic enzymes elucidating a regulatory net work of expression of genes involved in 5-aminolevulinicacid and tetrapyrrole biosynthesis.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delphi, India.

ABSTRACT
Light absorbed by colored intermediates of chlorophyll biosynthesis is not utilized in photosynthesis; instead, it is transferred to molecular oxygen, generating singlet oxygen ((1)O(2)). As there is no enzymatic detoxification mechanism available in plants to destroy (1)O(2), its generation should be minimized. We manipulated the concentration of a major chlorophyll biosynthetic intermediate i.e., protochlorophyllide in Arabidopsis by overexpressing the light-inducible protochlorophyllide oxidoreductase C (PORC) that effectively phototransforms endogenous protochlorophyllide to chlorophyllide leading to minimal accumulation of the photosensitizer protochlorophyllide in light-grown plants. In PORC overexpressing (PORCx) plants exposed to high-light, the (1)O(2) generation and consequent malonedialdehyde production was minimal and the maximum quantum efficiency of photosystem II remained unaffected demonstrating that their photosynthetic apparatus and cellular organization were intact. Further, PORCx plants treated with 5-aminolevulinicacid when exposed to light, photo-converted over-accumulated protochlorophyllide to chlorophyllide, reduced the generation of (1)O(2) and malonedialdehyde production and reduced plasma membrane damage. So PORCx plants survived and bolted whereas, the 5-aminolevulinicacid-treated wild-type plants perished. Thus, overexpression of PORC could be biotechnologically exploited in crop plants for tolerance to (1)O(2)-induced oxidative stress, paving the use of 5-aminolevulinicacid as a selective commercial light-activated biodegradable herbicide. Reduced protochlorophyllide content in PORCx plants released the protochlorophyllide-mediated feed-back inhibition of 5-aminolevulinicacid biosynthesis that resulted in higher 5-aminolevulinicacid production. Increase of 5-aminolevulinicacid synthesis upregulated the gene and protein expression of several downstream chlorophyll biosynthetic enzymes elucidating a regulatory net work of expression of genes involved in 5-aminolevulinicacid and tetrapyrrole biosynthesis.

Show MeSH
Related in: MedlinePlus