CAREER: Is phytohormone crosstalk the mechanism that predisposes drought-stressed conifers to bark beetle attack?

职业：植物激素串扰是导致干旱胁迫的针叶树容易遭受树皮甲虫攻击的机制吗？

• 批准号: 2046109
• 负责人: Thomas Davis
• 金额: $ 50万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-15 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2046109&HistoricalAwards=false
• 关键词: CAREER; phytohormone; crosstalk; mechanism; predisposes

Large bark beetle outbreaks have occurred across the landscape of western North America during the past two decades with dramatic ecological and economic impacts for public and private lands. There is growing evidence that trees are predisposed to bark beetle attack by environmental conditions, especially water stress. Consequently, regional droughts could set the stage for rapid beetle population growth that leads to outbreaks and large-scale forest mortality. However, it remains unclear exactly why drought-stressed trees become more susceptible to bark beetle attack--one possibility is that drought stress inhibits the ability of trees to defend themselves. Although trees do not have an adaptive immune system like animals, many conifers are able to recognize and respond to cell damage from insects by producing toxic chemicals in their resin. Production of these toxins are signaled by hormones that may be functionally impaired when water stress occurs prior to beetle attack. The goal of this work is to examine how drought stress interferes with hormone production and sensitivity in conifers and determine whether this interference underlies patterns of forest mortality across landscapes. Broader impacts include elements of experiential learning in STEM, mentoring of underrepresented student populations, development of new educational materials for school-age children, and science communication to broad audiences. To survive biological and environmental stress events, plants have evolved biochemical signaling pathways to reprogram their phenotypes appropriately in response to specific challenges. Although insect herbivore outbreaks are often preceded by environmental stress events that reduce the ability of plants to resist herbivory, physiological mechanisms underlying these interactions are not understood. This is an important gap in the field of plant-insect interactions as it precludes our ability to connect pattern with process in many natural ecosystems. One process-based explanation for this pattern is that conserved hormone receptors drive reduced sensitivity of plants to defense elicitors when environmental stress precedes a biological challenge. This project will identify controls over conifer tree defenses and develop new theory in chemical ecology using multiple Engelmann spruce (Picea engelmanni) populations, the North American spruce bark beetle (Dendroctonus rufipennis), and a beetle-associated symbiotic fungus (Leptographium abietinum) as the study system. The research plan addresses four interconnected research hypotheses: (1) trees respond differently to different types of biotic challenge through producing hormones, (2) sensitivity to these hormones drives chemical and physical defenses, (3) hormone-driven defensive induction reduces beetle population performance, and (4) environmental stress suppresses the ability of trees to respond to hormones and thus mount an appropriate defensive response. Addressing these collective hypotheses will elucidate the signaling mechanisms that link patterns of ecosystem disturbance with basic physiological processes and describe population-based variation in hormone sensitivity and defensive induction in a long-lived tree species.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.

在过去的二十年中，西部北美西部的景观发生了大型树皮甲虫暴发，对公共和私人土地产生了巨大的生态和经济影响。越来越多的证据表明，树木易受环境条件，尤其是水压力的树皮甲虫的攻击。因此，区域干旱可能为快速甲虫的种群增长奠定了基础，从而导致爆发和大规模的森林死亡率。但是，目前尚不清楚为什么干旱胁迫的树木更容易受到树皮甲虫攻击的影响 - 一种可能性是干旱压力阻碍了树木捍卫自己的能力。尽管树木没有像动物这样的自适应免疫系统，但许多针叶树能够通过在树脂中产生有毒化学物质来识别并应对细胞损害。这些毒素的产生由激素发出信号，这些激素可能在甲虫攻击之前出现水应力时会受到功能障碍。这项工作的目的是检查针叶树中干旱胁迫如何干扰激素的产生和敏感性，并确定这种干扰是否构成了跨景观的森林死亡模式。更广泛的影响包括STEM中体验式学习的要素，指导代表性不足的学生人群，开发针对学龄儿童的新教育材料以及与广泛受众的科学沟通。为了在生物学和环境压力事件中生存，植物已经进化了生化信号通路，以适当地对其表型重编程，以应对特定挑战。尽管昆虫的食草动物暴发通常是在环境压力事件之前降低植物抵抗草食的能力的，但这些相互作用的生理机制尚不清楚。这是植物与植物相互作用领域的重要差距，因为它排除了我们在许多自然生态系统中将模式与过程联系起来的能力。对这种模式的一种基于过程的解释是，当环境压力面临生物学挑战之前，保守的激素受体会降低植物对防御引起的敏感性。该项目将使用多个Engelmann Spruce（Picea Engelmanni）种群，北美云杉树皮甲虫（Dendroctonus rufipennis）和甲虫相关的共生型fungus（leptographium fungus（leptographium abietinum））作为研究系统来确定对针叶树防御能力的控制，并发展化学生态学的新理论。研究计划解决了四个相互联系的研究假设：（1）树木通过产生激素对不同类型的生物挑战的反应不同，（2）对这些激素的敏感性驱动化学和物理防御，（3）激素驱动的防御性诱导诱导甲壳虫的人口绩效，以及（4）环境压力对树木的能力抑制了适当的防御能力，从而响应了适当的防御力。解决这些集体假设将阐明将生态系统障碍的模式与基本生理过程联系起来的信号机制，并描述长期存在的树种中基于人群的激素敏感性和防御性诱导的差异。这奖反映了NSF的法定任务，并通过使用基础的智力效果和广泛的范围来评估，这是值得评估的。

项目成果

Nutritional Profile and Ecological Interactions of Yeast Symbionts Associated with North American Spruce Beetle (Dendroctonus rufipennis)

与北美云杉甲虫 (Dendroctonus rufipennis) 相关的酵母共生体的营养状况和生态相互作用

• DOI: 10.1007/s00248-022-02158-7
• 发表时间: 2022
• 期刊: Microbial Ecology
• 影响因子: 3.6
• 作者: Davis, Thomas S.;Stewart, Jane E.;Clark, Caitlin;Van Buiten, Charlene
• 通讯作者: Van Buiten, Charlene