Developmental and genetic dynamics of ambrosia beetle-fungal partner symbioses

文心兰甲虫滋生在树上，它们在树皮中挖洞产卵。这些甲虫的独特之处在于，它们还藏有真菌，作为它们的食物来源，这些真菌生长在树木组织上。然后，其中一些真菌可以感染树木，在一些情况下，可能会导致寄主树木在感染后几个月内死亡。这些甲虫及其病原真菌广泛存在于世界各地，对林业和自然生态系统构成重大威胁。然而，目前还没有研究仙人掌甲虫-真菌配对的遗传模型。本方案将以Xyloborus金龟子-月桂枯萎病菌(Harringtonia Lauricola)为模型。原始甲虫和真菌都入侵了美国，并正在迅速蔓延到美国东南部。甲虫将真菌带到树上，在树上，真菌能够杀死原本健康的树木。有超过500种不同种类的树木被甲虫用作宿主，包括沼泽树、红海湾树、沙棘树，以及在农业上重要的鳄梨作物，唯一的治疗方法是砍伐和焚烧这些树。在这个项目中，我们将研究甲虫如何庇护它的真菌伴侣的动力学和遗传学，包括甲虫如何选择、促进真菌的生长以及将真菌从寄主树带到寄主树。这些数据可以提供基本信息，最终可以用来帮助阻止这些树木病原体的传播。此外，该项目将为高中、本科生、研究生和博士后提供关于真菌生物学、疾病、共生和进化过程的培训和推广机会。研究人员将与佛罗里达大学的项目合作，为高中教师和普通公众开发关于真菌-昆虫共生的教育材料。昆虫-真菌互惠关系在自然界中广泛存在，而文心兰甲虫-真菌的相互作用代表了一些已知的最古老和最成功的共生现象。这种真菌是甲虫唯一的营养来源，这些甲虫在树上挖洞形成画廊，在那里种植并“种植”这种真菌作为食物。这些甲虫进化出专门的结构(霉菌囊)，容纳、运输和传播真菌。这些真菌和甲虫在整个进化史上共同适应了共生的生活方式，包括不同类型的真菌共生体的独立进化。这种名为Harringtonia lauricola的真菌是一种极具破坏性的树木病原体，影响鳄梨和樟科其他成员，仅在美国就已导致3亿棵树死亡。H.lauricola是其最初的入侵甲虫携带者(对美国)的互惠合作伙伴，现在可能已经传播到当地的甲虫物种。我们将研究月桂花甲虫和Xyleborus甲虫之间的发育和遗传机制。该项目将使用细胞和遗传方法来测试关于共生关系的具体假设。我们将：(1)探索真菌定植的细胞动力学，包括使用微生物学和细胞(例如，显微)方法调查真菌在真菌中的选择、持久性/维持、周转和竞争；(2)识别调节真菌共生的遗传机制，例如，哪些真菌基因/网络对真菌在真菌中的定殖和适合性是重要的；以及(3)构建基因表达谱(即，该奖项反映了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，认为值得支持。

Ambrosia beetles infest trees, where they dig into the bark to lay their eggs. These beetles are unique in that they also harbor fungi that act as their food source which grows on the tree tissues. Some of these fungi can then infect the tree and in several cases can result in the death of host trees within months of infection. These beetles and their pathogenic fungi occur worldwide and pose a significant threat to forestry and natural ecosystems. However, no genetic models for the study of any ambrosia beetle-fungal partner pairings are available. This proposal will use the Xyloborus beetle-laurel wilt pathogenic fungus (Harringtonia lauricola) as a model. Both the original beetle and the fungus are invasive to the United States and are rapidly spreading throughout the Southeastern part of the country. The beetle carries the fungus to trees, where the fungus is capable of killing otherwise healthy trees. There are over 500 different species of trees that the beetle uses as a host including swampbay, redbay, sassafras, and the agriculturally important crop of avocado, where the only treatment is to cut and burn the trees. In this project, we will study the dynamics and genetics of how the beetle harbors its fungal partner, including how the beetle chooses, promotes the growth of, and carries the fungus from host tree to host tree. These data can provide foundational information that can ultimately be used to help stop the spread of these tree pathogens. In addition, the project will provide opportunities for training and outreach to high school, undergraduate, graduate, and postdoctoral students on fungal biology, disease, symbioses and evolutionary processes. In partnership with programs at University of Florida, the investigator will develop educational material for the high school teachers and the general public on fungal-insect symbioses. Insect-fungal mutualisms are widespread in nature and ambrosia beetle-fungal interactions represent some of the oldest and most successful symbioses known. The fungus serves as the sole source of nutrition for the beetles that burrow into trees to form galleries where they grow and “farm” the fungus for food. These beetles have evolved specialized structures (mycangia) that house, transport and disseminate the fungus. These fungi and beetles have co-adapted to symbiotic lifestyles throughout evolutionary history and include independent evolutions of different types of mycangia that house different fungal symbionts. The fungus, Harringtonia lauricola is a highly destructive tree pathogen affecting avocado and other members of the Lauraceae family and has killed 300 million trees in the US alone. H. lauricola is the mutualistic partner to its original invasive (to the US) beetle carrier (Xyleborus glabratus) and may have now spread to indigenous beetle species. We will investigate the developmental and genetic mechanisms which underlie the relationship between H. lauricola and Xyleborus beetles. The project will use cellular and genetic approaches to test specific hypotheses concerning symbiotic association. We will: (1) probe the cellular dynamics of mycangial colonization, including investigating selection, persistence/maintenance, turnover, and competition in the mycangia using microbiological and cellular (e.g., microscopic) methods, (2) identify genetic mechanisms that mediate fungal symbioses, e.g., what fungal genes/network are important for colonization and fitness within the mycangia, and (3) construct gene expression profiles (i.e., transcriptomics) of the fungus during mycangial colonization to help define the evolutionary processes that has led to fungal-mycangial symbioses.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.