Regulation of extrafloral nectar secretion by jasmonates in lima bean is light dependent
Regulation of extrafloral nectar secretion by jasmonates in lima bean is light dependent
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DOI：
10.1073/pnas.1009007107
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发表时间：
2010-09
期刊：
影响因子：
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通讯作者：
V. Radhika;Christian Kost;A. Mithöfer;W. Boland
中科院分区：
文献类型：
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作者：
V. Radhika;Christian Kost;A. Mithöfer;W. Boland
为了最大限度地提高适应性，植物需要感知光环境的变化，并相应地调整其生理反应。这些变化是否以及如何影响它们对食草动物的防御反应的调节在很大程度上仍然不清楚。我们通过研究利马豆（Phaseolus lunatus）的花外花蜜（EFN）的分泌来解决这个问题，该花蜜被植物激素茉莉酸（JA）激活，并作为对草食动物的间接防御机制。我们发现，植物的EFN分泌响应JA是光依赖性的：在黑暗中，JA减少EFN分泌，而在光照条件下，JA诱导EFN分泌相对于控制。这种调制受到光的光谱组成的影响[即，红与远红（R：FR）辐射的比率]，但不是光强度。这些发现表明，JA对EFN分泌的独特差异效应取决于环境光条件。有趣的是，用异亮氨酸-JA缀合物（JA-Ile）处理在光照条件下增强EFN分泌，但在黑暗中不减少EFN分泌。此外，在光暴露的植物中抑制Ile生物合成显著降低EFN分泌速率。这种减少可以通过额外应用JA-Ile来恢复，表明JA-Ile是上调EFN分泌所需的活性化合物。最后，对机械损伤植物的实验表明，光是形成JA-Ile所必需的，而不是JA。这些结果表明，在利马豆中，光环境调节植物对茉莉酸的响应以及JA-Ile生物合成，其控制随后的EFN分泌。
To maximize fitness, plants need to perceive changes in their light environment and adjust their physiological responses accordingly. Whether and how such changes also affect the regulation of their defense responses against herbivores remains largely unclear. We addressed this issue by studying the secretion of extrafloral nectar (EFN) in lima bean (Phaseolus lunatus), which is known to be activated by the phytohormone jasmonic acid (JA) and functions as an indirect defense mechanism against herbivores. We found that the plant’s EFN secretion in response to JA was light dependent: In the dark, JA reduced EFN secretion, whereas under light conditions, JA induced EFN secretion relative to controls. This modulation was affected by the light’s spectral composition [i.e., ratio of red to far-red (R:FR) radiation], but not light intensity. These findings demonstrate a unique differential effect of JA on EFN secretion depending on the ambient light conditions. Interestingly, treatment with the isoleucine–JA conjugate (JA–Ile) enhanced EFN secretion under light conditions yet did not reduce EFN secretion in the dark. Moreover, inhibition of Ile biosynthesis in light-exposed plants significantly decreased the EFN secretion rate. This reduction could be recovered by additional application of JA–Ile, suggesting that JA–Ile is the active compound required to up-regulate EFN secretion. Finally, experiments with mechanically damaged plants revealed that light was required for the formation of JA–Ile, but not of JA. These results demonstrate that in lima bean, the light environment modulates the plant’s response to jasmonates as well as JA–Ile biosynthesis, which controls the subsequent EFN secretion.