RUI: EPIGENETIC WEAPONS IN PLANT-HERBIVORE INTERACTIONS: SULFORAPHANE AS A NATURAL HISTONE DEACETYLASE INHIBITOR IN LEPIDOPTERAN PESTS

该项目将研究一种新型的“表观遗传武器”，十字花科植物利用这种武器来对抗破坏性的害虫。表观遗传系统通过暂时打开或关闭染色体片段来调节数百个基因的表达，从而使这些片段中的基因能够被激活或去激活。这些系统指导着正常的生长和发育，并使个人能够对不断变化的环境做出快速反应。最近，观察到萝卜硫素是一种来自十字花科植物(如花椰菜、花椰菜)的天然物质，它在昆虫幼虫吃植物叶子的过程中扰乱了它们的表观遗传控制系统。因此，萝卜硫素可能是一种对抗害虫的表观遗传武器。这将代表一种新的植物防御类别，有可能破坏昆虫的发育，从而保护农作物。初步数据表明，萝卜硫素对害虫毛虫的防治效果与剂量、温度和害虫种类有关。多面手似乎最容易受到这种物质的影响。相比之下，共同进化为以这些植物为食的专业昆虫似乎已经通过某种未知的机制产生了部分抗药性。为了探索这种抗性机制，将研究三种重要经济害虫在不同温度下消耗不同剂量萝卜硫素时的幼虫发育。实验将确定这种物质对(1)幼虫的生存和发育，(2)成虫和蝴蝶的健康，(3)这些昆虫的表观遗传控制系统，以及(4)与重要代谢途径和过程相关的基因表达的影响。也将评估萝卜硫素引起的表观遗传变化可能挥之不去，影响可能没有食用这种物质的后代的可能性。该项目可能会为保护作物植物提供新的方法，并提高我们对植物如何影响昆虫种群的理解。它还将在三年内支持一个不同的约20名本科生群体的教育，为这些学生在相关领域从事研究生和专业水平的工作做好准备。十字花科植物产生萝卜硫素(SFN)，这是一种核组蛋白脱乙酰酶(HDACs)的抑制剂，已被研究为一种潜在的药物和膳食补充剂。在人类中，萝卜硫素的摄入在几分钟内就会改变酶的活性、DNA与组蛋白的结合和基因表达。然而，SFN在自然界中作为HDAC抑制剂的能力，扰乱草食昆虫的表观遗传机制的能力，从未被探索过。有人提出，植物可以利用SFN作为“表观遗传武器”。初步数据表明，饲料中的SFN显著降低了军虫(甜菜夜蛾)的HDAC活性，减缓了其发育，有时还会影响第二代幼虫。相反，卷心菜环纹夜蛾似乎对SFN有部分抗性。为了进一步探索这一点，研究人员将确定SFN如何改变以这些植物为食的三种食草动物的第一代和第二代幼虫的发育、HDAC活性、组蛋白乙酰化和全球基因表达：菜青虫(卷心菜白)、菜青虫(甘蓝环虫)和甜菜夜蛾(军虫)。这些反应将在一定的温度范围内进行检查。RNA-SEQ将用于分析差异基因表达，将识别同源基因组，将使用基因本体论分类预测差异表达基因的假定功能，并将差异表达基因映射到代谢途径。拟议中的实验将首次验证植物HDAC抑制剂可以干扰昆虫表观遗传机制的假设。这将代表一种新的植物防御类别。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project will investigate a novel “epigenetic weapon” that cruciferous plants deploy against destructive insect pests. Epigenetic systems regulate the expression of hundreds of genes by temporarily opening or closing chromosomal segments so that the genes in these segments can be activated or de-activated. These systems direct normal growth and development and allow individuals to respond rapidly to changing environments. Recently, it has been observed that sulforaphane, a natural substance from cruciferous plants (e.g., broccoli, cauliflower), disrupts the epigenetic control systems of insect larvae while they eat plant leaves. Thus, sulforaphane may serve as an epigenetic weapon against pest insects. This would represent a new category of plant defense, one with the potential to sabotage insect development and thereby protect crop plants. Preliminary data indicate that the effectiveness of sulforaphane against pest caterpillars depends on the dosage, the temperature, and the pest species. Generalist feeders seem to be most susceptible to this substance. In contrast, specialist insects which co-evolved to feed upon these plants seem to have developed partial resistance, by some unknown mechanism. To explore this mechanism of resistance, the larval development of three economically important pest species will be examined as they consume various doses of sulforaphane over a range of temperatures. Experiments will determine the impacts of this substance on (1) larval survival and development, (2) the health of adult moths and butterflies, (3) the epigenetic control systems of these insects, and (4) the expression of genes associated with important metabolic pathways and processes. The possibility that the epigenetic changes induced by sulforaphane may linger, affecting future generations which may not have consumed this substance, will also be evaluated. This project may suggest new methods for protecting crop plants and improve our understanding how plants influence insect populations. It will also support the education of a diverse group of ~20 undergraduates over three years, preparing these students for graduate- and professional-level work in related fields. Cruciferous plants produce sulforaphane (SFN), an inhibitor of nuclear histone deacetylases (HDACs) which has been investigated as a potential drug and dietary supplement. In humans, sulforaphane consumption alters enzyme activity, DNA-histone binding, and gene expression within minutes. However, the ability of SFN to act as a HDAC inhibitor in nature, disrupting the epigenetic machinery of herbivorous insects, has never been explored. It is proposed that plants can employ SFN as an “epigenetic weapon”. Preliminary data demonstrate that dietary SFN dramatically reduces the HDAC activity and slows development of the army worm (Spodoptera exigua), sometimes affecting second-generation larvae. In contrast, the cabbage looper (Trichoplusia ni) seems to be partially resistant to SFN. To explore this further, the investigators will determine how SFN alters development, HDAC activity, histone acetylation, and global gene expression in 1st and 2nd generation larvae of three herbivores which feed on these plants: Pieris rapae (cabbage white), Trichoplusia ni (cabbage looper), Spodoptera exigua (army worm). These responses will be examined over a range of temperatures. RNA-seq will be used to analyze differential gene expression, orthologous gene groups will be identified, the putative function of differentially expressed genes will be predicted using gene ontology classifications, and differentially expressed genes will be mapped to metabolic pathways. The proposed experiments would, for the first time, test the hypothesis that plant HDAC inhibitors can interfere with the epigenetic machinery of insects. This would represent a new category of plant defense.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.