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Pale-green phenotype of atl31atl6 double mutant leaves is caused by disruption of 5-aminolevulinic acid biosynthesis in Arabidopsis thaliana.

Maekawa S, Takabayashi A, Huarancca Reyes T, Yamamoto H, Tanaka A, Sato T, Yamaguchi J - PLoS ONE (2015)

Bottom Line: Plastid ultrastructure and Blue Native-PAGE analyses revealed that pale-green leaves contain abnormal plastid structure with highly reduced levels of thylakoid proteins.The expression of key transcription factor GLK1, which directly promotes HEMA1 transcription, was also significantly decreased in atl31/atl6 mutant.Finally, application of 5-aminolevulinic acid to the atl31/atl6 mutants resulted in recovery to a green phenotype.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Science and Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido, Japan.

ABSTRACT
Arabidopsis ubiquitin ligases ATL31 and homologue ATL6 control the carbon/nitrogen nutrient and pathogen responses. A mutant with the loss-of-function of both atl31 and atl6 developed light intensity-dependent pale-green true leaves, whereas the single knockout mutants did not. Plastid ultrastructure and Blue Native-PAGE analyses revealed that pale-green leaves contain abnormal plastid structure with highly reduced levels of thylakoid proteins. In contrast, the pale-green leaves of the atl31/atl6 mutant showed normal Fv/Fm. In the pale-green leaves of the atl31/atl6, the expression of HEMA1, which encodes the key enzyme for 5-aminolevulinic acid synthesis, the rate-limiting step in chlorophyll biosynthesis, was markedly down-regulated. The expression of key transcription factor GLK1, which directly promotes HEMA1 transcription, was also significantly decreased in atl31/atl6 mutant. Finally, application of 5-aminolevulinic acid to the atl31/atl6 mutants resulted in recovery to a green phenotype. Taken together, these findings indicate that the 5-aminolevulinic acid biosynthesis step was inhibited through the down-regulation of chlorophyll biosynthesis-related genes in the pale-green leaves of atl31/atl6 mutant.

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Fv/Fm measurement.Effect of light conditions on the Fv/Fm of first or second true leaves of 2-week-old WT and atl31–1/atl6–1 plants grown under ML or LL conditions. Error bars represent SD (n = 5). Statistical significance was determined by ANOVA, followed by post-hoc Tukey’s tests. Means that differed significantly (P<0.05) are indicated by different letters.
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pone.0117662.g005: Fv/Fm measurement.Effect of light conditions on the Fv/Fm of first or second true leaves of 2-week-old WT and atl31–1/atl6–1 plants grown under ML or LL conditions. Error bars represent SD (n = 5). Statistical significance was determined by ANOVA, followed by post-hoc Tukey’s tests. Means that differed significantly (P<0.05) are indicated by different letters.

Mentions: To determine whether the ratio of photo-damaged PSII was increased in the atl31–1/atl6–1 double mutant, we measured Fv/Fm, but found no significant difference between these plants and WT, even when grown under ML conditions (Fig. 5). This result, showing that the ratio of functional to total PSII in atl31–1/atl6–1 was comparable to that of WT, suggested that the pale-green phenotype of atl31–1/atl6–1 was not caused by high light-induced PSII photodamage. This finding, taken together with the normal Chl a/b ratio in atl31–1/atl6–1, suggests that the efficiency of photosynthesis in pale-green leaves of the double mutant was not damaged, although the photoreactive capacity could be reduced under ML conditions.


Pale-green phenotype of atl31atl6 double mutant leaves is caused by disruption of 5-aminolevulinic acid biosynthesis in Arabidopsis thaliana.

Maekawa S, Takabayashi A, Huarancca Reyes T, Yamamoto H, Tanaka A, Sato T, Yamaguchi J - PLoS ONE (2015)

Fv/Fm measurement.Effect of light conditions on the Fv/Fm of first or second true leaves of 2-week-old WT and atl31–1/atl6–1 plants grown under ML or LL conditions. Error bars represent SD (n = 5). Statistical significance was determined by ANOVA, followed by post-hoc Tukey’s tests. Means that differed significantly (P<0.05) are indicated by different letters.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4338271&req=5

pone.0117662.g005: Fv/Fm measurement.Effect of light conditions on the Fv/Fm of first or second true leaves of 2-week-old WT and atl31–1/atl6–1 plants grown under ML or LL conditions. Error bars represent SD (n = 5). Statistical significance was determined by ANOVA, followed by post-hoc Tukey’s tests. Means that differed significantly (P<0.05) are indicated by different letters.
Mentions: To determine whether the ratio of photo-damaged PSII was increased in the atl31–1/atl6–1 double mutant, we measured Fv/Fm, but found no significant difference between these plants and WT, even when grown under ML conditions (Fig. 5). This result, showing that the ratio of functional to total PSII in atl31–1/atl6–1 was comparable to that of WT, suggested that the pale-green phenotype of atl31–1/atl6–1 was not caused by high light-induced PSII photodamage. This finding, taken together with the normal Chl a/b ratio in atl31–1/atl6–1, suggests that the efficiency of photosynthesis in pale-green leaves of the double mutant was not damaged, although the photoreactive capacity could be reduced under ML conditions.

Bottom Line: Plastid ultrastructure and Blue Native-PAGE analyses revealed that pale-green leaves contain abnormal plastid structure with highly reduced levels of thylakoid proteins.The expression of key transcription factor GLK1, which directly promotes HEMA1 transcription, was also significantly decreased in atl31/atl6 mutant.Finally, application of 5-aminolevulinic acid to the atl31/atl6 mutants resulted in recovery to a green phenotype.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Science and Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido, Japan.

ABSTRACT
Arabidopsis ubiquitin ligases ATL31 and homologue ATL6 control the carbon/nitrogen nutrient and pathogen responses. A mutant with the loss-of-function of both atl31 and atl6 developed light intensity-dependent pale-green true leaves, whereas the single knockout mutants did not. Plastid ultrastructure and Blue Native-PAGE analyses revealed that pale-green leaves contain abnormal plastid structure with highly reduced levels of thylakoid proteins. In contrast, the pale-green leaves of the atl31/atl6 mutant showed normal Fv/Fm. In the pale-green leaves of the atl31/atl6, the expression of HEMA1, which encodes the key enzyme for 5-aminolevulinic acid synthesis, the rate-limiting step in chlorophyll biosynthesis, was markedly down-regulated. The expression of key transcription factor GLK1, which directly promotes HEMA1 transcription, was also significantly decreased in atl31/atl6 mutant. Finally, application of 5-aminolevulinic acid to the atl31/atl6 mutants resulted in recovery to a green phenotype. Taken together, these findings indicate that the 5-aminolevulinic acid biosynthesis step was inhibited through the down-regulation of chlorophyll biosynthesis-related genes in the pale-green leaves of atl31/atl6 mutant.

Show MeSH