The phytohormone auxin is a component of the regulatory system that controls UV-mediated accumulation of flavonoids and UV-induced morphogenesis.
In plants, ultraviolet (UV)-B acclimation is a complex, dynamic process that plays an essential role in preventing UV-B damage to targets such as DNA and the photosynthetic machinery. In this study we tested the hypothesis that the phytohormone auxin is a component of the regulatory system that controls both UV-mediated accumulation of flavonoids and UV-induced morphogenesis. We found that the leaf area of Arabidopsis thaliana Col-0 plants raised under a low dose of UV radiation (0.56 kJ m(-2)  daily dose) was, on average, decreased by 23% relative to plants raised in the absence of UV-B, and this was accompanied by a decrease (P = 0.063) in free auxin in young leaf tissues. Compared to Col-0, both the auxin influx mutant axr4-1 and the auxin biosynthesis mutant nit1-3 displayed significantly stronger morphogenic responses, i.e. relative decreases in leaf area were greater for these two mutants. UV exposure also induced accumulation of flavonoids. In Col-0, increases in the concentrations of specific kaempferol derivatives ranged from 2.1- to 19-fold. Thus, UV induces complex changes in flavonoid-glycosylation patterns. Compared to Col-0, three auxin mutants displayed significantly different flavonoid profiles. Thus, based on mutant analysis, it is concluded that the phytohormone auxin plays a role in UV acclimation by regulating flavonoid concentration, flavonoid-glycosylation pattern and by controlling UV-induced morphogenic responses.
Laboratory of Molecular Physiology and Biotechnology, Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Kathleen
K
Hectors
Sandra
S
van Oevelen
Yves
Y
Guisez
Els
E
Prinsen
Marcel A K
MA
Jansen
D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects; D005419:Flavonoids / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D013058:Mass Spectrometry; D009024:Morphogenesis; D014466:Ultraviolet Rays
D005419:Flavonoids; D007210:Indoleacetic Acids