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Pure Appl. Chem., Vol. 70, No. 11, pp. 2118, 1998

 

Insect juvenile hormone III in the sedge, Cyperus iria L.: Distribution and possible biological significance*

J.C. Bede¹, W.G. Goodman² and S.S. Tobe¹

1. Department of Zoology, University of Toronto, Toronto ON M5S 3G5, Canada
2. Department of Entomology, University of Wisconsin, Madison WI 53706, U.S.A.
E-mail: [email protected]

Abstract: One defensive strategy of plants against insect herbivory is the production of secondary metabolites which interfere with insect physiological functions (ref. 4 and references therein). Compounds which mimic insect juvenile hormone activity or inhibit the biosynthesis of these compounds have been identified in plants, but in 1988, insect juvenile hormone III (JH III), methyl-10R,11-epoxy-3,7,11-trimethyl 2E,6E-dodecadienoate, and its biosynthetic precursor (insects), methyl farnesoate, were isolated from the sedges Cyperus iria L. and C. aromaticus (Ridley) Mattf and Kük (ref. 1).

The distribution of JH III in seven month-old mature plants of C. iria was determined using a radioimmunoassay. In these plants, the highest concentration of JH III was found in the roots (27.2 � 3.3 m g/g FW); this is approximately 500 and 300 times the amount found in either the inflorescence (fruits, inflorescence, bracts) or leaves, respectively. This suggests that the roots may be the site of biosynthesis; alternatively, JH III may be synthesized in the leaves and transported to the root tissue. Although, this profile is maintained over the course of development, there is a decrease in JH III concentration as the plant enters early flowering; this probably reflects the influx of energy and metabolites into the growing tissue and illustrates the dynamic nature of this compound in the plant tissues.

The isolation of JH IIII from the sedges C. iria and C. aromaticus, in conjunction with the high concentrations found in C. iria throughout development and the extraction of structurally similar compounds from closely related and other plant species suggests that this compound may have an important biological function(s) in the plant. It is likely that JH III may be involved in plant-insect, plant-plant (allelopathic), plant-nematode or plant-fungal interactions in the sedge C. iria.

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* Invited lecture presented at the International Conference on Bioversity and Bioresources: Conservation and Utilization, 23-37 November 1997, Phuket, Thailand.

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