title: Semiochemicals from ex situ abiotically stressed cactus tissue: a contributing role of fungal spores?
abstract: Semiochemicals play a central role in communication between plants and insects, such as signaling the location of a suitable host. Fungi on host plants can also play an influential role in communicating certain plant vulnerabilities to an insect. The spiroketal conophthorin is an important semiochemical produced by developing fungal spores. Spiroketals are also used as signals for scolytid communication. Plants and fungi are known to emit varying volatile profiles under biotic and abiotic stress. This paper reports distinctive temporal-volatile profiles from three abiotic treatments, room temperature (control), -15 °C (cold), and -15 °C to room temperature (shock), of cactus tissue plugs. Volatiles from the three treatments included monoterpenes from control plugs, compounds of varying classes and origin at later stages for cold plugs, and known semiochemicals, including spiroketals, at later stages for shock plugs. The results highlight several important findings: a unique tissue source of the spiroketals; abiotic cold-shock stress is indicated as the cause of spiroketal production; and, given previous findings of spirogenesis, fungal spore involvement is a probable biosynthetic origin of the spiroketals. These findings suggest an important role of fungal volatiles as signaling plant vulnerability to insects.
authors.affiliation: Foodborne Toxin Detection and Prevention, Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture , 800 Buchanan Street, Albany, California 94710, United States.
authors.forename: John J
authors.initials: JJ
authors.lastname: Beck
authors.forename: Nausheena
authors.initials: N
authors.lastname: Baig
authors.forename: Daniel
authors.initials: D
authors.lastname: Cook
authors.forename: Noreen E
authors.initials: NE
authors.lastname: Mahoney
authors.forename: Travis D
authors.initials: TD
authors.lastname: Marsico
mesh_terms: D000818:Animals; D029421:Cactaceae / Q000254:growth & development / Q000382:microbiology*; D005658:Fungi / Q000254:growth & development / Q000378:metabolism*; D005663:Furans / Q000378:metabolism; D007313:Insecta / Q000502:physiology; D010675:Pheromones / Q000096:biosynthesis*; D013141:Spiro Compounds / Q000378:metabolism; D013172:Spores, Fungal / Q000254:growth & development / Q000378:metabolism*
chemical_list: D005663:Furans; D010675:Pheromones; D013141:Spiro Compounds; C520774:spiroketal
keywords: Opuntia humifusa; chalcogran; conophthorin; host plant volatiles; plant−insect−microbe interaction; spiroketal