AUTHOR=Vos Irene A., Verhage Adriaan , Schuurink Robert C., Watt Lewis G., Pieterse Corné M., Van Wees Saskia C.

TITLE=Onset of herbivore-induced resistance in systemic tissue primed for jasmonate-dependent defenses is activated by abscisic acid

JOURNAL=Frontiers in Plant Science

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2013.00539

DOI=10.3389/fpls.2013.00539

ISSN=1664-462X

ABSTRACT=<p>In <italic>Arabidopsis</italic>, the MYC2 transcription factor on the one hand and the AP2/ERF transcription factors ORA59 and ERF1 on the other hand regulate distinct branches of the jasmonic acid (JA) signaling pathway in an antagonistic fashion, co-regulated by abscisic acid (ABA) and ethylene, respectively. Feeding by larvae of the specialist herbivorous insect <italic>Pieris rapae</italic> (small cabbage white butterfly) results in activation of the MYC-branch and concomitant suppression of the ERF-branch in insect-damaged leaves. Here we investigated differential JA signaling activation in undamaged systemic leaves of <italic>P. rapae</italic>-infested plants. We found that the <italic>MYC2</italic> transcription factor gene was induced both in the local insect-damaged leaves and the systemic undamaged leaves of <italic>P. rapae</italic>-infested <italic>Arabidopsis</italic> plants. However, in contrast to the insect-damaged leaves, the undamaged tissue did not show activation of the MYC-branch marker gene <italic>VSP1</italic>. Comparison of the hormone signal signature revealed that the levels of JA and (+)-7-<italic>iso</italic>-jasmonoyl-<sc>L</sc>-isoleucine raised to similar extents in locally damaged and systemically undamaged leaves, but the production of ABA and the JA precursor 12-oxo-phytodienoic acid was enhanced only in the local herbivore-damaged leaves, and not in the distal undamaged leaves. Challenge of undamaged leaves of pre-infested plants with either <italic>P. rapae</italic> larvae or exogenously applied ABA led to potentiated expression levels of <italic>MYC2</italic> and <italic>VSP1</italic>, with the latter reaching extremely high expression levels. Moreover, <italic>P. rapae</italic>-induced resistance, as measured by reduction of caterpillar growth on pre-infested plants, was blocked in the ABA biosynthesis mutant <italic>aba2-1</italic>, that was also impaired in <italic>P. rapae</italic>-induced expression of <italic>VSP1</italic>. Together, these results suggest that ABA is a crucial regulator of herbivore-induced resistance by activating primed JA-regulated defense responses upon secondary herbivore attack in <italic>Arabidopsis</italic>.</p>