Presymptomatic visualization of plant−virus interactions by thermography
Laury Chaerle1, Wim Van Caeneghem1, Eric Messens1, Hans Lambers2, Marc Van Montagu1
& Dominique Van Der Straeten1
1
Laboratorium voor Genetica, Departement Plantengenetica,
Vlaams Interuniversitair Instituut voor Biotechnologie, Universiteit Gent
, K.L. Ledeganckstraat 35, B-9000
Gent, Belgium.
2
Plant Sciences, Faculty of Agriculture, The University
of Western Australia, Nedland, WA 6907,
Australia and Department of Plant Ecology and Evolutionary Biology,
Utrecht University, NL-3584 CA Utrecht,
The Netherlands.
Correspondence should be addressed to Dominique Van Der Straeten dostr@gengenp.rug.ac.beinfrared thermographyplant-pathogen interactionrespirationsalicylic acidTMVtobaccotranspiration
Salicylic acid (SA), produced by plants as a signal in defense against
pathogens, induces metabolic heating mediated by alternative respiration in
flowers of thermogenic plants, and, when exogenously applied, increases leaf
temperature in nonthermogenic plants. We have postulated that the latter phenomenon
would be detectable when SA is synthesized locally in plant leaves. Here,
resistance to tobacco mosaic virus (TMV) was monitored thermographically before
any disease symptoms became visible on tobacco leaves. Spots of elevated temperature
that were confined to the place of infection increased in intensity from 8
h before the onset of visible cell death, and remained detectable as a halo
around the ongoing necrosis. Salicylic acid accumulates during the prenecrotic
phase in TMV-infected tobacco and is known to induce stomatal closure in certain
species. We show that the time course of SA accumulation correlates with the
evolution of both localized thermal effect and stomatal closure. Since the
contribution of leaf respiration is marginal, we concluded that the thermal
effect results predominantly from localized, SA-induced stomatal closure.
The presymptomatic temperature increase could be of general significance in
incompatible plant−pathogen interactions.
