Jasmonic acid enhances plant cyanogenesis and resistance to herbivory in lima bean.
Jasmonic acid (JA) is a natural plant hormone ubiquitously distributed in plants and centrally involved in the induction of direct and indirect plant defenses. Defenses up-regulated by this hormone include trichomes--a direct, mechanical defense--and alkaloids--a direct chemical defense--as well as two indirect chemical defenses: volatile organic compounds (VOCs) and extrafloral nectar (EFN). Plant cyanogenesis--the release of toxic hydrogen cyanide (HCN) from preformed cyanogenic precursors in fruits, leaves, and seeds of many plants--is recognized as a direct, constitutive plant defensive trait, and is among the most widely distributed of all direct chemical plant defenses. The cyanogenic system in plants is composed of three parameters: The cyanogenic potential (HCNp; concentration of cyanogenic precursors), β-glucosidase activity, and cyanogenic capacity (HCNc; release of gaseous hydrogen cyanide). Here, we demonstrated that experimental application of aqueous solutions of JA ranging from 0.001 to 1.0 mmol L(-1), as well as insect herbivory significantly enhanced HCNc via the induction of β-glucosidase activity in wild lima bean (Phaseolus lunatus L.). In choice feeding trials with JA induced and damaged leaves, adult Mexican bean beetles--natural herbivores of lima bean--rejected leaves with enhanced β-glucosidase activity and HCNc. Our findings suggest that jasmonic acid plays a critical role in regulating activity of β-glucosidases, which determines the rate of cyanogenesis, and thus mediates direct plant defense against herbivores.
Department of Biology, Portland State University, 1719 SW 10th Ave, Portland, OR, 97201, USA.
Stefanie
S
Kautz
Julie A
JA
Trisel
Daniel J
DJ
Ballhorn
D000818:Animals; D001517:Coleoptera / Q000254:growth & development / Q000502:physiology*; D003517:Cyclopentanes / Q000378:metabolism*; D060434:Herbivory; D006856:Hydrogen Cyanide / Q000378:metabolism*; D007814:Larva / Q000502:physiology; D054883:Oxylipins / Q000378:metabolism*; D027805:Phaseolus / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D011897:Random Allocation; D001617:beta-Glucosidase / Q000378:metabolism
D003517:Cyclopentanes; D054883:Oxylipins; D006856:Hydrogen Cyanide; C011006:jasmonic acid; D001617:beta-Glucosidase