Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University Utrecht, Netherlands.
Department of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam Amsterdam, Netherlands.
Front Plant Sci. 2013 Dec 30;4:539. doi: 10.3389/fpls.2013.00539. eCollection 2013.
In Arabidopsis, 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 Pieris rapae (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 P. rapae-infested plants. We found that the MYC2 transcription factor gene was induced both in the local insect-damaged leaves and the systemic undamaged leaves of P. rapae-infested Arabidopsis plants. However, in contrast to the insect-damaged leaves, the undamaged tissue did not show activation of the MYC-branch marker gene VSP1. Comparison of the hormone signal signature revealed that the levels of JA and (+)-7-iso-jasmonoyl-L-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 P. rapae larvae or exogenously applied ABA led to potentiated expression levels of MYC2 and VSP1, with the latter reaching extremely high expression levels. Moreover, P. rapae-induced resistance, as measured by reduction of caterpillar growth on pre-infested plants, was blocked in the ABA biosynthesis mutant aba2-1, that was also impaired in P. rapae-induced expression of VSP1. 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 Arabidopsis.
在拟南芥中，一方面 MYC2 转录因子，另一方面 AP2/ERF 转录因子 ORA59 和 ERF1，以拮抗的方式调节茉莉酸（JA）信号通路的不同分支，分别受脱落酸（ABA）和乙烯的共同调控。鳞翅目专食性昆虫菜粉蝶（小菜蛾）幼虫的取食导致 MYC 分支的激活，同时伴随受损叶片中 ERF 分支的抑制。在这里，我们研究了受损的系统叶片中不同的 JA 信号激活。我们发现，MYC2 转录因子基因在局部受损叶片和系统未受损叶片中均被诱导。然而，与受损叶片不同的是，未受损组织没有激活 MYC 分支标记基因 VSP1。激素信号特征的比较表明，JA 和（+）-7-异茉莉酰基-L-异亮氨酸的水平在局部受损和系统未受损叶片中均升高到相似程度，但 ABA 和 JA 前体 12-氧代-植二烯酸的产生仅在局部食草动物受损叶片中增强，而在远端未受损叶片中没有增强。用菜粉蝶幼虫或外源施加的 ABA 对预侵染植物的未受损叶片进行处理，导致 MYC2 和 VSP1 的表达水平增强，后者达到极高的表达水平。此外，用 P. rapae 幼虫或外源 ABA 处理预侵染植物的未受损叶片，导致 ABA 生物合成突变体 aba2-1 中 P. rapae 诱导的 VSP1 表达受阻，且该突变体也会抑制 P. rapae 诱导的抗性，这表明 ABA 是通过激活预先存在的 JA 调节的防御反应来调控植物对二次食草动物攻击的抗性的关键调节剂。
