Arabidopsis mutants lacking phenolic sunscreens exhibit enhanced ultraviolet-B injury and oxidative damage.
We have assessed ultraviolet-B (UV-B)-induced injury in wild-type Arabidopsis thaliana and two mutants with altered aromatic secondary product biosynthesis. Arabidopsis mutants defective in the ability to synthesize UV-B-absorbing compounds (flavonoids in transparent testa 5 [tt5] and sinapate esters in ferulic acid hydroxylase 1 [fah1]) are more sensitive to UV-B than is the wild-type Landsberg erecta. Despite its ability to accumulate UV-absorptive flavonoid compounds, the ferulic acid hydroxylase mutant fah1 exhibits more physiological injury (growth inhibition and foliar lesions) than either wild type or tt5. The extreme UV-B sensitivity of fah1 demonstrates the importance of hydroxycinnamate esters as UV-B protectants. Consistent with the whole-plant response, the highest levels of lipid and protein oxidation products were seen in fah1. Ascorbate peroxidase enzyme activity was also increased in the leaves of UV-B-treated plants in a dose- and genotype-dependent manner. These results demonstrate that, in A. thaliana, hydroxycinnamates are more effective UV-B protectants than flavonoids. The data also indicate that A. thaliana responds to UV-B as an oxidative stress, and sunscreen compounds reduce the oxidative damage caused by UV-B.
Landry
L G
LG
Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, New York 14853-1801, USA.
Chapple
C C
CC
Last
R L
RL
D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects*; D029681:Arabidopsis Proteins; D060387:Ascorbate Peroxidases; D003577:Cytochrome P-450 Enzyme System; D004307:Dose-Response Relationship, Radiation; D005419:Flavonoids / Q000378:metabolism*; D015227:Lipid Peroxidation; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010544:Peroxidases / Q000378:metabolism / Q000528:radiation effects; D010636:Phenols / Q000378:metabolism*; D018515:Plant Leaves; D010940:Plant Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
D029681:Arabidopsis Proteins; D005419:Flavonoids; D010636:Phenols; D010940:Plant Proteins; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010544:Peroxidases; D060387:Ascorbate Peroxidases; C097486:CYP84A1 protein, Arabidopsis