PLANT PHYSIOLOGY , Vol 112, Issue 2 787-792, Copyright © 1996 by American Society of Plant Biologists
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PLANT-MICROBE AND PLANT-INSECT INTERACTIONS |
Transport of Salicylic Acid in Tobacco Necrosis Virus-Infected Cucumber Plants
W. Molders, A. Buchala and J. P. Metraux
Institut de Biologie Vegetale, Universite de Fribourg, CH 1700 Fribourg, Switzerland
The transport of salicylic acid (SA) was studied in cucumber (Cucumis
sativus L.) using 14C-labeled benzoic acid that was injected in the
cotyledons at the time of inoculation. Primary inoculation with tobacco
necrosis virus (TNV) on the cotyledons led to an induction of systemic
resistance of the first primary leaf above the cotyledon against
Colletotrichum lagenarium as early as 3 d after inoculation. [14C]SA was
detected in the phloem or in the first leaf 2 d after TNV inoculation,
whereas [14C]benzoic acid was not detected in the phloem during the first 3
d after TNV inoculation of the cotyledons, indicating phloem transport of
[14C]SA from cotyledon. In leaf 1, the specific activity of [14C]SA
decreased between 1.7 and 8.6 times compared with the cotyledons,
indicating that, in addition to transport, leaf 1 also produced more SA.
The amount of SA transported after TNV infection of the cotyledon was 9 to
160 times higher than in uninfected control plants. Thus, SA can be
transported to leaf 1 before the development of systemic acquired
resistance, and SA accumulation in leaf 1 results both from transport from
the cotyledon and from synthesis in leaf 1.