Review of the chemical ecology of homoterpenes in arthropod–plant interactions

Abstract

The homoterpenes 4,8-dimethyl-1,3,7-nonatriene (DMNT) and 4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) are volatile products of plant metabolism reported from diverse plant taxa and multiple plant tissues. As such, they have a range of potential ecological functions. Here, we review the key literature to assess evidence for roles in contrasting plant-arthropod interactions. TMTT, and DMNT especially, have been reported as sometimes dominant constituents of floral scents from angiosperm taxa ranging from primitive Magnoliales to more advanced, taxonomic orders of economic significance such as Fabales and Sapindales. Although all taxa producing TMTT and DMNT in floral scents are entomophilous ('insect pollinated'), experimental evidence for an assumed role of these homoterpenes in pollinator attraction is limited. Representing a trade-off, in some cases, homoterpenes in floral scents have been shown to act as kairomones, attracting herbivores. Additionally, both TMTT and DMNT are released by plant foliage in response to arthropod feeding, mechanical damage simulating feeding, or even egg deposition. Evidence for a functional role in herbivore-induced plant volatile (HIPV) blends comes from a wide range of angiosperm orders, including anemophilous ('wind pollinated') taxa, as well as from gymnosperms. We conclude by considering how TMTT and DMNT function in community-level interactions and highlighting research priorities that will reveal how plants avoid tradeoffs from contrasting ecological functions of DMNT and TMTT release and how homoterpene production might be exploited to develop improved crop varieties.

Characterization of CrufCSP1 and Its Potential Involvement in Host Location by Cotesia ruficrus (Hymenoptera: Braconidae), an Indigenous Parasitoid of Spodoptera frugiperda (Lepidoptera: Noctuidae) in China

“…Interestingly, all volatile organic compounds (VOCs) demonstrating affinity with CrufCSP1 were characterized by their polarity and a carbon structure of less than 10. However, some important compounds for natural enemies, such as DMNT and TMTT in their foraging behaviors for hosts and prey [49,50], were not bound by CrufCSP1. This observation suggests the likelihood of other CrufCSPs playing a role in the perception of crucial plant volatiles and apolar compounds.…”

Arabidopsis Transcriptomics Reveals the Role of Lipoxygenase2 (AtLOX2) in Wound-Induced Responses

“…Wounding of arabidopsis leaves results in the biosynthesis and release of volatile organic compounds (VOCs) that are involved in numerous ecological roles, including intra-plant stress signaling and tritrophic interactions, such as attracting parasitoids or predators of the herbivore [ 128 , 129 ]. From the diterpenoid precursor geranylgeranyl diphosphate, AtTPS04, which is expressed in arabidopsis non-glandular trichomes [ 50 ], catalyzes the production of (Ε,Ε)-geranyllinalool, which is converted by AtCYP82G1 into volatile 4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT) [ 49 ], an important attractant in tritrophic interactions for beneficial parasitoid and predatory arthropods [ 130 ]. AtTPS04 is induced in response to herbivory by caterpillars of the specialist diamond backmoth, Plutella xylostella , or the generalist African cotton leafworm, Spodoptera littoralis [ 131 , 132 , 133 , 134 ].…”

Integration of RNA-Seq and Metabolite Analysis Reveals the Key Floral Scent Biosynthetic Genes in Herbaceous Peony

“…As an example, 2-PE mediates both direct and indirect plant defenses, as well as attracting pollinators such as beetles, bees, and butterflies [49]. Terpenes such as β-caryophyllene play roles in mutualistic interactions, plant defense, and insect attraction [50][51][52]. Geraniol, an acyclic monoterpene, possesses anti-microbial, antifeedant, and insect repellant activities [53].…”