Plant–Plant Signaling: Application of trans- or cis-Methyl Jasmonate Equivalent to Sagebrush Releases Does Not Elicit Direct Defenses in Native Tobacco

Abstract

Nicotiana attenuata plants growing in close proximity to damaged sagebrush (Artemisia tridentata ssp. tridentata) suffer less herbivory than plants near undamaged sagebrush. Sagebrush constitutively releases methyl jasmonate (MeJA), a compound that when applied directly to N. attenuata, elicits herbivore resistance and the direct defense traits [protease inhibitors (PIs), nicotine]. Damage increases the release of volatile MeJA, primarily in the cis epimer, suggesting that cis-MeJA may mediate this apparent interplant signaling. We characterized sagebrush's MeJA plume before and after damage in nature and in the laboratory, and compared the activity of trans- and cis-MeJA in inducing PIs, nicotine, and Manduca sexta resistance in N. attenuata. We used both lanolin applications and aqueous sprays that mimic natural exposures, and we determined the amount of volatilized MeJA required to elicit a nicotine response in open-grown plants. Wounding rapidly and transiently increased cis-MeJA emissions from damaged parts (but not systemically), and the released plume did not rapidly dissipate in nature. cis-MeJA was not consistently more active than trans-MeJA, and the order of exposure (trans- then cis-) did not influence activity. We conclude that volatile MeJA, either trans- or cis-, when applied at levels consistent with those released by sagebrush does not elicit direct defenses in N. attenuata.