Chemical defense against insects in Heterotheca subaxillaris and three Orobanchaceae species using exudates from trichomes

Abstract

Background One of the roles of plant trichomes is thought to be reducing feeding damage from herbivores. Among trichomes, glandular trichomes play a role in chemical defense systems in plants by means of stored biologically active phytochemicals. These phytochemicals act as pest repellents. They show antimicrobial and insecticidal activities, and they have also been isolated and identified from wild plants. Results The Asteraceae species Heterotheca subaxillaris has many glandular trichomes on the leaf surface, and these contain sesquiterpene carboxylates, which show insect antifeedant activity. Because these sesquiterpene carboxylates are major constituents of glandular trichomes, they may act as a chemical defense in H. subaxillaris. The Orobanchaceae species Parentucellia viscosa also has many glandular trichomes on the leaf surface and produces an insect antifeedant clerodane‐type diterpene, kolavenic acid, in these trichomes. Additionally, two other Orobanchaceae species, Bellardia trixago and Parentucellia latifolia, also have many glandular trichomes, but the constituents of these glandular trichomes did not show biological activities against test insects. However, the seco‐labdane diterpene alcohol trixagol and its hemi‐malonate were major constituents in B. trixago, and these terpenes may act as physical defenses against herbivores by interfering with feeding due to their viscosity. Conclusion The secondary metabolites from glandular trichomes of H. subaxillaris and P. viscosa showed insect antifeedant activity, and these secondary metabolites were presumed to act as chemical defenses for these plant species. On the other hand, non‐biologically active secondary metabolites produced by two other Orobanchaceae, B. trixago and P. latifolia, were presumed to act as physical defenses due to their viscosity. Defense systems such as these may be applicable to new crop breeding to enhance protection against insect pests. © 2019 Society of Chemical Industry

Comparative transcriptomics analysis revealing flower trichome development during flower development in two Lonicera japonica Thunb. cultivars using RNA-seq

“…Plant trichomes are epidermal outgrowths that protect plants from the attack of herbivorous insects, which develop even when plants are grown under optimal conditions [ 9 ]. Interestingly, plasticity allows plants to respond to insect attacks by increasing the population and density of trichomes in new growing leaves, stems, and flowers [ 10 ].…”

Chemical Defense of Yacón (Smallanthus sonchifolius) Leaves against Phytophagous Insects: Insect Antifeedants from Yacón Leaf Trichomes

“…In a function of glandular trichomes, a tomato cultivar without hairy trichomes produced large amounts of terpenoids compared with its cultivar with a hairy trichomes, and these terpenoids contribute to the herbivore resistance in tomato plants [ 15 ]. Additionally, plant trichomes can physically interfere with insect locomotion over the leaf surface and as a consequence avoid feeding damage from the herbivores [ 16 ]. In particular, most glandular trichomes synthesize and store various biologic active compounds with herbivore repellent and antimicrobial activities and they may provide a function as a chemical defense system for them.…”

“…& Rusby was disclosed to produce and store sesquiterpene carboxylates in glandular trichomes on the leaf surface. These sesquiterpenes was found to exhibit phytotoxicity and insect antifeedant activity [ 16 , 17 ]. The Orobanchaceae weeds yellow bartsia ( Parentucellia viscosa (L.) Caruel., syn.…”

“…Bartsia trixago L.) also produce large amounts of exudates consisting of diterpenes for tiny insect entrapment on the trichomes of their leaf surface. The trichome density and insect antifeedant diterpene, kolavenic acid in glandular trichomes were both important for herbivore resistance of yellow bartsia [ 16 ].…”

Comparative transcriptomics analysis revealing flower trichome development during flower development in two Lonicera Japonica Thunb. cultivars using RNA-seq

“…Plant trichomes are epidermal outgrowths that protect plants from the attack of herbivorous insects, which develop even when plants are grown under optimal conditions [6]. Interestingly, plasticity allows plants to respond to insect attacks by increasing the population and density of trichomes in new growing leaves, stems, and flowers [7].…”