Regulation of herbivore-induced defenses responses by benzoxazinoids in Zea mays

植物产生各种各样的有毒和威慑代谢物来保护自己免受食草动物和病原体的侵害。在大多数物种中，化学防御的诱导产生是由经过充分研究的信号分子调节的，特别是水杨酸和茉莉酸。然而，进化理论和最近的实验证据都表明，正如植物物种之间产生防御性代谢物的多样性一样，植物用于防御信号传导的小分子也存在物种特异性差异。玉米（Zea mays）是世界上最重要的作物植物之一，DIMBOA（2,4-二羟基-7-甲氧基-1,4-苯并恶嗪-3- 1）及其衍生物，统称为苯并恶嗪类化合物，构成了一类主要的防御相关化合物。除了对食草动物和病原体的直接毒性外，DIMBOA还需要诱导外质体胼胝质沉积，以防御韧皮部吸吮昆虫食草动物的摄食和真菌菌丝的细胞间生长。在苯并恶嗪类药物代谢调节的另一个例子中，DIMBOA及其分解产物可以干扰生长素的感知，从而直接影响植物的生长发育。为了研究DIMBOA和其他苯并杂嗪类化合物作为植物信号分子的重要性，我将解决两个主要的研究目标：1)我将研究以前未知的玉米防御调节方面，不仅确定胼胝质的上调机制，而且确定DIMBOA调节的其他防御反应。2)我将在分子水平上研究DIMBOA和生长素之间的相互作用，从而发现植物防御和发育之间新的调控联系。我在博伊斯·汤普森研究所和康奈尔大学提出的研究计划将结合遗传学、基因组学、生物化学、生理学和生物信息学方法。在我的宿主实验室产生的玉米突变系，以及玉米自交系的自然变异，将使我能够研究DIMBOA作为一种信号分子在体内和体外的调节功能。我对植物内部化学通讯的研究不仅将为调节防御诱导和生长的新信号通路提供新的见解，而且还将使分子育种方法得以实施，以生产具有天然增强的草食和病原体抗性的玉米。这个综合的玉米研究项目，加上我将在我的主办机构接受的其他培训，将为我回到德国后在学术界的研究生涯做好充分的准备。

Plants produce a wide variety of toxic and deterrent metabolites to protect themselves against herbivores and pathogens. In most species, the inducible production of chemical defenses is regulated by well-studied signaling molecules, in particular, salicylic acid and jasmonic acid. However, both evolutionary theory and recent experimental evidence suggest that, just as there is great diversity in the production of defensive metabolites among plant species, there is also species-specific variation in the small molecules that plants implement for defense signaling.In maize (Zea mays), one of the world’s most important crop plants, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) and its derivatives, collectively called benzoxazinoids, constitute a major class of defense-related compounds. In addition to its direct toxicity against herbivores and pathogens, DIMBOA is required for inducing apoplastic callose deposition as a defense against both feeding by phloem-sucking insect herbivores and intercellular growth of fungal hyphae. In a further example of metabolic regulation by benzoxazinoids, DIMBOA and its breakdown products can perturb auxin perception, thereby directly influencing plant growth and development. To investigate the importance of DIMBOA and other benzoxazinoids as plant signaling molecules, I will address two main research objectives: 1) I will investigate previously unknown aspects of maize defense regulation, identifying not only the mechanism of callose up-regulation, but also other defense responses that are regulated by DIMBOA. 2) I will examine the interactions between DIMBOA and auxin at the molecular level, thereby identifying new regulatory connections between plant defense and development.My proposed research program at the Boyce Thompson Institute and Cornell University will combine genetic, genomic, biochemical, physiological, and bioinformatics methods. Maize mutant lines generated in my host lab, as well as natural variation in maize inbred lines, will allow me to investigate regulatory functions of DIMBOA as a signaling molecule in vivo and in vitro. My investigation of chemical communication within plants not only will provide new insights into novel signaling pathways that regulate both defense induction and growth, but also will enable the implementation of molecular breeding approaches to produce maize with naturally enhanced herbivore and pathogen resistance. This integrated maize research program, together with other training that I will receive at my host institution, will make me well-prepared for a future research career in academia when I return to Germany.