Plant Physiol, July 2001, Vol. 126, pp. 1012-1023
Phenol-Oxidizing Peroxidases Contribute to the Protection of
Plants from Ultraviolet Radiation Stress1
Marcel A.K.
Jansen,*
Ria E.
van den Noort,
M.Y. Adillah
Tan,
Els
Prinsen,
L. Mark
Lagrimini, and
Roger N.F.
Thorneley
Department of Biological Chemistry, John Innes Centre, Norwich
Research Park, Norwich NR4 7UH, United Kingdom (M.A.K.J., R.N.F.T.);
Department of Plant Physiology, Wageningen Agricultural University,
Arboretumlaan 4, 6703BD Wageningen, The Netherlands (M.A.K.J.,
R.E.v.d.N., M.Y.A.T.); Department of Biology, University of
Antwerp, B-2610 Antwerpen, Belgium (E.P.); and Novartis
Agribusiness Biotechnology Research Inc., Research Triangle Park, North
Carolina 27709 (L.M.L.)
We have studied the mechanism of UV protection in two duckweed
species (Lemnaceae) by exploiting the UV sensitivity of photosystem II
as an in situ sensor for radiation stress. A UV-tolerant
Spirodela punctata G.F.W. Meyer ecotype had
significantly higher indole-3-acetic acid (IAA) levels than a
UV-sensitive ecotype. Parallel work on Lemna gibba
mutants suggested that UV tolerance is linked to IAA degradation rather
than to levels of free or conjugated IAA. This linkage is consistent
with a role for class III phenolic peroxidases, which have been
implicated both in the degradation of IAA and the cross-linking of
various UV-absorbing phenolics. Biochemical analysis revealed increased
activity of a specific peroxidase isozyme in both UV-tolerant duckweed
lines. The hypothesis that peroxidases play a role in UV protection was
tested in a direct manner using genetically modified tobacco
(Nicotiana sylvestris). It was found that increased
activity of the anionic peroxidase correlated with increased tolerance
to UV radiation as well as decreased levels of free auxin. We conclude
that phenol-oxidizing peroxidases concurrently contribute to UV
protection as well as the control of leaf and plant architecture.
1
M.A.K.J. was supported by the Royal Netherlands
Academy of Arts and Sciences and by the European Community
(Training, Mobility, and Research Network "Peroxidases in
Agriculture, the Environment, and Industry," contract no.
ERB-FMRXCT-980200).
*
Corresponding author; e-mail Marcel.Jansen{at}BBSRC.AC.UK; fax
44-1603-450018.
© 2001 American Society of Plant Physiologists
