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Arimura G, Kopke S, Kunert M, Volpe V, David A, Brand P, Dabrowska P, Maffei ME, Boland W: Effects of feeding Spodoptera littoralis on lima bean leaves: IV. Plant Physiol. 2008 Mar;146(3):965-73. Epub 2007 Dec 28.
Diurnal and nocturnal damage differentially initiate plant volatile emission.. Continuous mechanical damage initiates the rhythmic emission of volatiles in lima bean (Phaseolus lunatus) leaves; the emission resembles that induced by herbivore damage. The effect of diurnal versus nocturnal damage on the initiation of plant defense responses was investigated using MecWorm, a robotic device designed to reproduce tissue damage caused by herbivore attack. Lima bean leaves that were damaged by MecWorm during the photophase emitted maximal levels of beta-ocimene and (Z)-3-hexenyl acetate in the late photophase. Leaves damaged during the dark phase responded with the nocturnal emission of (Z)-3-hexenyl acetate, but with only low amounts of beta-ocimene; this emission was followed by an emission burst directly after the onset of light. In the presence of (13) CO (2), this light-dependent synthesis of beta-ocimene resulted in incorporation of 75% to 85% of (13) C, demonstrating that biosynthesis of beta-ocimene is almost exclusively fueled by the photosynthetic fixation of CO (2) along the plastidial 2-C-methyl-D-erythritol 4-P pathway. Jasmonic acid (JA) accumulated locally in direct response to the damage and led to immediate up-regulation of the P. lunatus beta-ocimene synthase gene (PlOS) independent of the phase, that is, light or dark. Nocturnal damage caused significantly higher concentrations of JA (approximately 2-3 times) along with enhanced expression levels of PlOS. Transgenic Arabidopsis thaliana transformed with PlOS promoter :: beta-glucuronidase fusion constructs confirmed expression of the enzyme at the wounded sites. In summary, damage-dependent JA levels directly control the expression level of PlOS, regardless of light or dark conditions, and photosynthesis is the major source for the early precursors of the 2-C-methyl-D-erythritol 4-P pathway. |
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