Schoenherr Andrew P, Rizzo Eric, Jackson Natasha, Manosalva Patricia, Gomez S Karen
School of Biological Sciences, University of Northern Colorado, Greeley, CO.
Microbiology and Plant Pathology Department, University of California, Riverside, University Avenue, Riverside, CA.
Environ Entomol. 2019 Apr 3;48(2):370-381. doi: 10.1093/ee/nvy195.
Most plants form mutualistic associations with arbuscular mycorrhizal (AM) fungi that are ubiquitous in soils. Through this symbiosis, plants can withstand abiotic and biotic stresses. The underlying molecular mechanisms involved in mediating mycorrhiza-induced resistance against insects needs further research, and this is particularly true for potato (Solanum tuberosum L. (Solanales: Solanaceae)), which is the fourth most important crop worldwide. In this study, the tripartite interaction between potato, the AM fungus Rhizophagus irregularis (Glomerales: Glomeraceae), and cabbage looper (Trichoplusia ni Hübner) (Lepidoptera: Noctuidae) was examined to determine whether potato exhibits mycorrhiza-induced resistance against this insect. Plant growth, insect fitness, AM fungal colonization of roots, and transcript levels of defense-related genes were measured in shoots and roots after 5 and 8 d of herbivory on mycorrhizal and nonmycorrhizal plants. AM fungal colonization of roots did not have an effect on potato growth, but root colonization levels increased by herbivory. Larval weight gain was reduced after 8 d of feeding on mycorrhizal plants compared with nonmycorrhizal plants. Systemic upregulation of Allene Oxide Synthase 1 (AOS1), 12-Oxo-Phytodienoate Reductase 3 (OPR3) (jasmonic acid pathway), Protease Inhibitor Type I (PI-I) (anti-herbivore defense), and Phenylalanine Ammonia Lyase (PAL) transcripts (phenylpropanoid pathway) was found during the tripartite interaction. Together, these findings suggest that potato may exhibit mycorrhiza-induced resistance to cabbage looper by priming anti-herbivore defenses aboveground. This study illustrates how mycorrhizal potato responds to herbivory by a generalist-chewing insect and serves as the basis for future studies involving tripartite interactions with other pests.
大多数植物与土壤中普遍存在的丛枝菌根（AM）真菌形成共生关系。通过这种共生，植物能够抵御非生物和生物胁迫。介导菌根诱导的抗虫性的潜在分子机制需要进一步研究，对于全球第四大重要作物马铃薯（Solanum tuberosum L.（茄目：茄科））而言尤其如此。在本研究中，检测了马铃薯、AM真菌不规则球囊霉（Rhizophagus irregularis（球囊霉目：球囊霉科））和甘蓝夜蛾（Trichoplusia ni Hübner）（鳞翅目：夜蛾科）之间的三方相互作用，以确定马铃薯是否表现出菌根诱导的对这种昆虫的抗性。在菌根植物和非菌根植物遭受食草动物取食5天和8天后，测量了地上部和根部的植物生长、昆虫适合度、AM真菌在根部的定殖以及防御相关基因的转录水平。AM真菌在根部的定殖对马铃薯生长没有影响，但食草动物取食使根部定殖水平增加。与非菌根植物相比，取食菌根植物8天后幼虫体重增加减少。在三方相互作用过程中发现丙二烯氧化物合酶1（AOS1）、12-氧代-植物二烯酸还原酶3（OPR3）（茉莉酸途径）、I型蛋白酶抑制剂（PI-I）（抗食草动物防御）和苯丙氨酸解氨酶（PAL）转录本（苯丙烷途径）的系统性上调。总之，这些发现表明马铃薯可能通过启动地上部的抗食草动物防御来表现出菌根诱导的对甘蓝夜蛾的抗性。本研究阐明了菌根马铃薯如何对多食性咀嚼昆虫的取食做出反应，并为未来涉及与其他害虫三方相互作用的研究奠定了基础。
