Limits...
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.

Show MeSH

Related in: MedlinePlus

Physiological responses of PORCx plants to ALA-mediated oxidative stress.Both WT and T-13 plants were grown and treated with ALA (3 mM) and leaf samples were taken for analysis immediately prior (0 h) or after different duration of light (100 µmoles photons m−2 s−1) exposure. (A) Fv/Fm ratio and electron transport rate (B, C) of ALA-treated light exposed WT and T-13 plants as monitored by PAM 2100 fluorometer and values are mean ± SD (n = 20). (D) Ion leakage as a measure of damage to plasma membrane in ALA-treated light exposed WT and T-13 plants. (E) MDA contents of ALA-treated light exposed WT and T-13 plants. All the above experiments were performed thrice and each data point is the average of 3 replicates. The error bar represents ± SD.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3198771&req=5

pone-0026532-g007: Physiological responses of PORCx plants to ALA-mediated oxidative stress.Both WT and T-13 plants were grown and treated with ALA (3 mM) and leaf samples were taken for analysis immediately prior (0 h) or after different duration of light (100 µmoles photons m−2 s−1) exposure. (A) Fv/Fm ratio and electron transport rate (B, C) of ALA-treated light exposed WT and T-13 plants as monitored by PAM 2100 fluorometer and values are mean ± SD (n = 20). (D) Ion leakage as a measure of damage to plasma membrane in ALA-treated light exposed WT and T-13 plants. (E) MDA contents of ALA-treated light exposed WT and T-13 plants. All the above experiments were performed thrice and each data point is the average of 3 replicates. The error bar represents ± SD.

Mentions: To ascertain if ALA-induced oxidative stress affected photosynthetic quantum yield, Fv/Fm ratio was monitored in ALA-treated WT and PORCx plants. The Fv/Fm ratio of dark-incubated ALA-treated WT plants were reduced by 32%, 46%, and 63% respectively after 1 h, 2 h and 6 h of light exposure. Under identical conditions PORCx plants had no substantial decrease of Fv/Fm ratio (Figure 7A). There was no change in initial F0 fluorescence in WT and PORCx plants up to 6 h of light exposure.


Overexpression of protochlorophyllide oxidoreductase C regulates oxidative stress in Arabidopsis.

Pattanayak GK, Tripathy BC - PLoS ONE (2011)

Physiological responses of PORCx plants to ALA-mediated oxidative stress.Both WT and T-13 plants were grown and treated with ALA (3 mM) and leaf samples were taken for analysis immediately prior (0 h) or after different duration of light (100 µmoles photons m−2 s−1) exposure. (A) Fv/Fm ratio and electron transport rate (B, C) of ALA-treated light exposed WT and T-13 plants as monitored by PAM 2100 fluorometer and values are mean ± SD (n = 20). (D) Ion leakage as a measure of damage to plasma membrane in ALA-treated light exposed WT and T-13 plants. (E) MDA contents of ALA-treated light exposed WT and T-13 plants. All the above experiments were performed thrice and each data point is the average of 3 replicates. The error bar represents ± SD.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0026532-g007: Physiological responses of PORCx plants to ALA-mediated oxidative stress.Both WT and T-13 plants were grown and treated with ALA (3 mM) and leaf samples were taken for analysis immediately prior (0 h) or after different duration of light (100 µmoles photons m−2 s−1) exposure. (A) Fv/Fm ratio and electron transport rate (B, C) of ALA-treated light exposed WT and T-13 plants as monitored by PAM 2100 fluorometer and values are mean ± SD (n = 20). (D) Ion leakage as a measure of damage to plasma membrane in ALA-treated light exposed WT and T-13 plants. (E) MDA contents of ALA-treated light exposed WT and T-13 plants. All the above experiments were performed thrice and each data point is the average of 3 replicates. The error bar represents ± SD.
Mentions: To ascertain if ALA-induced oxidative stress affected photosynthetic quantum yield, Fv/Fm ratio was monitored in ALA-treated WT and PORCx plants. The Fv/Fm ratio of dark-incubated ALA-treated WT plants were reduced by 32%, 46%, and 63% respectively after 1 h, 2 h and 6 h of light exposure. Under identical conditions PORCx plants had no substantial decrease of Fv/Fm ratio (Figure 7A). There was no change in initial F0 fluorescence in WT and PORCx plants up to 6 h of light exposure.

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