The transcriptional regulator BZR1 mediates trade-off between plant innate immunity and growth.
The transcriptional regulator BZR1 mediates trade-off between plant innate immunity and growth.
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DOI：
10.7554/elife.00983
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发表时间：
2013-12-31
期刊：
影响因子：
7.7
通讯作者：
Zipfel C
中科院分区：
文献类型：
--
作者：
Lozano-Durán R;Macho AP;Boutrot F;Segonzac C;Somssich IE;Zipfel C
植物先天免疫和类固醇介导的生长之间的权衡的分子机制是有争议的。在这里，我们报告说，激活转录因子BZR 1是必需的，足以抑制免疫信号的油菜素类固醇（BR）。BZR 1诱导多种WRKY转录因子的表达，这些转录因子对早期免疫反应具有负控制作用。此外，BZR 1与WRKY 40结合，介导BR与免疫信号之间的拮抗作用。我们发现，BZR 1介导的免疫抑制是特别相关的植物快速生长时，需要，如在黄化。因此，BZR 1作为一个重要的调节剂介导的生长和免疫力之间的权衡整合的环境线索。http://dx.doi.org/10.7554/eLife.00983.001像所有的有机体一样，植物必须小心地平衡它们的资源。投资于新根或新叶的生长可以使植物更好地利用其环境，但它不能以使植物容易受到害虫和病原体的攻击为代价。因此，在分配资源用于增长或防御疾病之间存在明显的权衡。这种权衡必须得到很好的平衡，还必须对环境中有利于增长或防御的不同线索做出反应。植物的免疫系统能够检测到入侵的微生物，并触发对它们的防御反应。在植物细胞的表面，一种叫做模式识别受体的蛋白质能够识别特定的分子，这些分子是微生物和病原体的标志，比如细菌用来移动的分子尾部的蛋白质。对于许多模式识别受体来说，它们已经识别出潜在入侵微生物的信号需要称为BAK 1的辅助受体的作用。有趣的是，BAK 1还与识别油菜素类固醇的受体相互作用，油菜素类固醇是刺激植物生长的激素。由于生长和功能性免疫系统都依赖于BAK 1，因此假设对这种辅助受体的竞争可能在植物中这两个过程之间的权衡中发挥作用。然而，这种解释是有争议的，这种权衡的机制仍然需要澄清。现在，Lozano-Durán等人已经推翻了BAK 1竞争直接导致生长和免疫之间权衡的观点。通过研究BAK 1如何与植物模式物种拟南芥中的免疫受体相互作用，这种权衡实际上是独立于BAK 1的。相反，人们发现，一种名为BZR 1的蛋白质的激活会重新编程基因表达，以“关闭”免疫信号，从而对油菜素类固醇做出反应。Lozano-Durán等人还表明，BZR 1允许生长和免疫力之间的权衡平衡根据环境的提示而改变。BZR 1对免疫系统的抑制在需要快速植物生长的条件下尤其明显，例如，当它们模仿幼苗从土壤中出现之前所经历的条件时，并且必须在饥饿之前快速生长以达到光照。DOI：http://dx.doi.org/10.7554/eLife.00983.002网站
The molecular mechanisms underlying the trade-off between plant innate immunity and steroid-mediated growth are controversial. Here, we report that activation of the transcription factor BZR1 is required and sufficient for suppression of immune signaling by brassinosteroids (BR). BZR1 induces the expression of several WRKY transcription factors that negatively control early immune responses. In addition, BZR1 associates with WRKY40 to mediate the antagonism between BR and immune signaling. We reveal that BZR1-mediated inhibition of immunity is particularly relevant when plant fast growth is required, such as during etiolation. Thus, BZR1 acts as an important regulator mediating the trade-off between growth and immunity upon integration of environmental cues. DOI: http://dx.doi.org/10.7554/eLife.00983.001 Like all organisms, plants must perform a careful balancing act with their resources. Investing in the growth of new roots or leaves can allow a plant to better exploit its environment—but it must not be at the expense of leaving the plant vulnerable to attack by pests and pathogens. As such, there is an obvious trade-off between allocating resources to growth or defense against disease. This trade-off must be finely balanced, and must also be responsive to different cues in the environment that would favor either growth or defense. The plant’s immune system is able to detect invading microbes, and trigger a defensive response against them. At the surface of plant cells, proteins called pattern recognition receptors are able to recognize specific molecules that are the tell-tale signs of microbes and pathogens—such as the proteins in the molecular tails that bacteria use to move around. For many pattern recognition receptors, signaling that they have recognized a potential invading microbe requires the actions of a co-receptor called BAK1. Interestingly, BAK1 also interacts with the receptor that identifies brassinosteroids—hormones that stimulate plant growth. Since growth and a functioning immune system are both reliant on BAK1, it was hypothesized that competition for this co-receptor could have a role in the trade-off between the two processes in plants. However, this explanation was controversial and the mechanisms underlying the trade-off still required clarification. Now, Lozano-Durán et al. have debunked the idea that competition for BAK1 is directly responsible for the trade-off between growth and immunity. By examining how BAK1 interacts with immune receptors in the plant model species Arabidopsis thaliana, the trade-off was actually shown to be independent of BAK1. Instead, it was discovered that activation of a protein, called BZR1, reprogramed gene expression to ‘switch off’ immune signaling in response to brassinosteroids. Lozano-Durán et al. also show that BZR1 allows the balance of the trade-off between growth and immunity to be shifted in response to cues from the environment. The suppression of the immune system by BZR1 was particularly pronounced when the conditions required fast plant growth—for example, when they mimicked the conditions experienced by seedlings before they emerge from the soil, and must grow swiftly to reach the light before they starve. DOI: http://dx.doi.org/10.7554/eLife.00983.002