Center for Medical, Agricultural and Veterinary Entomology, U.S. Department of Agriculture-Agricultural Research Service, 1700 SW 23rd Drive, Gainesville, FL, 32608, USA.
National Center for Agricultural Utilization Research, U.S. Department of Agriculture-Agricultural Research Service, 1815 N. University Street, Peoria, IL, 61604, USA.
Planta. 2019 Jan;249(1):21-30. doi: 10.1007/s00425-018-2999-2. Epub 2018 Sep 6.
Maize produces an array of herbivore-induced terpene volatiles that attract parasitoids to infested plants and a suite of pathogen-induced non-volatile terpenoids with antimicrobial activity to defend against pests. Plants rely on complex blends of constitutive and dynamically produced specialized metabolites to mediate beneficial ecological interactions and protect against biotic attack. One such class of metabolites are terpenoids, a large and structurally diverse class of molecules shown to play significant defensive and developmental roles in numerous plant species. Despite this, terpenoids have only recently been recognized as significant contributors to pest resistance in maize (Zea mays), a globally important agricultural crop. The current review details recent advances in our understanding of biochemical structures, pathways and functional roles of maize terpenoids. Dependent upon the lines examined, maize can harbor more than 30 terpene synthases, underlying the inherent diversity of maize terpene defense systems. Part of this defensive arsenal is the inducible production of volatile bouquets that include monoterpenes, homoterpenes and sesquiterpenes, which often function in indirect defense by enabling the attraction of parasitoids and predators. More recently discovered are a subset of sesquiterpene and diterpene hydrocarbon olefins modified by cytochrome P450s to produce non-volatile end-products such kauralexins, zealexins, dolabralexins and β-costic acid. These non-volatile terpenoid phytoalexins often provide effective defense against both microbial and insect pests via direct antimicrobial and anti-feedant activity. The diversity and promiscuity of maize terpene synthases, coupled with a variety of secondary modifications, results in elaborate defensive layers whose identities, regulation and precise functions are continuing to be elucidated.
玉米产生一系列草食性诱导萜烯挥发物，吸引寄生蜂到受感染的植物上，还产生一系列具有抗微生物活性的病原体诱导非挥发性萜类化合物，以抵御害虫。植物依赖于组成型和动态产生的特殊代谢物的复杂混合物来介导有益的生态相互作用并抵御生物攻击。萜类化合物就是这样一类代谢物，它们是一大类结构多样的分子，在许多植物物种中被证明具有重要的防御和发育作用。尽管如此，萜类化合物直到最近才被认为是玉米（Zea mays）抗虫的重要贡献者，玉米是一种全球重要的农业作物。本综述详细介绍了我们对玉米萜类化合物的生化结构、途径和功能作用的理解的最新进展。根据所检查的品系，玉米可以拥有 30 多种萜烯合酶，这说明了玉米萜烯防御系统的固有多样性。这种防御武器的一部分是诱导产生挥发性混合物，包括单萜、倍半萜和三萜，这些化合物通常通过促进寄生蜂和捕食者的吸引来发挥间接防御作用。最近发现的是一组倍半萜和二萜类碳氢化合物烯烃，经过细胞色素 P450 的修饰，产生非挥发性的终产物，如卡瓦雷林、zealexin、 dolabralexin 和 β-costic acid。这些非挥发性萜类植物抗毒素通常通过直接的抗菌和抗食作用为微生物和昆虫害虫提供有效的防御。玉米萜烯合酶的多样性和多功能性，加上各种次级修饰，导致了复杂的防御层，其身份、调控和精确功能仍在不断阐明。
