Loliolide, a Carotenoid Metabolite, Is a Potential Endogenous Inducer of Herbivore Resistance.

Jasmonic acid (JA) plays an important role in the induction of herbivore resistance in many plants. However, JA-independent herbivore resistance has been suggested. An herbivore-resistance-inducing substance was isolated from Tobacco mosaic virus-infected tobacco (Nicotiana tabacum) leaves in which a hypersensitive response (HR) was induced and identified as loliolide, which has been identified as a ß-carotene metabolite. When applied to tomato (Solanum lycopersicum) leaves, loliolide decreased the survival rate of the two-spotted spider mite, Tetranychus urticae, egg deposition by the same pest, and the survival rate of larvae of the common cutworm Spodoptera litura without exhibiting toxicity against these herbivores. Endogenous loliolide levels increased not only with an infestation by S litura larvae, but also with the exogenous application of their oral secretions in tomato. A microarray analysis identified cell-wall-associated defense genes as loliolide-responsive tomato genes, and exogenous JA application did not induce the expression of these genes. Suppressor of zeaxanthin-less (szl), an Arabidopsis (Arabidopsis thaliana) mutant with a point mutation in a key gene of the ß-carotene metabolic pathway, exhibited the decreased accumulation of endogenous loliolide and increased susceptibility to infestation by the western flower thrip (Frankliniella occidentalis). A pretreatment with loliolide decreased susceptibility to thrips in the JA-insensitive Arabidopsis mutant coronatine-insensitive1 Exogenous loliolide did not restore reduced electrolyte leakage in szl in response to a HR-inducing bacterial strain. These results suggest that loliolide functions as an endogenous signal that mediates defense responses to herbivores, possibly independently of JA, at least in tomato and Arabidopsis plants.

Effect of increased male and female age at mating on the reproductive performance of Cnaphalocrocis medinalis (Crambidae: Lepidoptera).

The success of mating disruption using synthetic sex pheromones depends not only on preventing mating, but also on delayed mating in the target insect. Using the rice leaffolder moth, Cnaphalocrocis medinalis (Guenée), we determined the effect of increased age at mating imposed on males only (male treatment), females only (female treatment),or on both sexes simultaneously (both sexes treatment). These increased age treatments had a negative effect on the percentage of mating, the total number of eggs, and the hatchability. The female reproductive performance in C. medinalis was decreased with increased moths' age. The both sexes treatment had the most potent negative effect on reproductive performance. Longevity of mated moths and duration of the preoviposition period in C. medinalis were not significantly different among these increased age treatments. The underlying mechanisms causing a decline in female reproductive performance of C. medinalis when increased age was imposed on males versus females and the potential of using mating disruption strategies to control the populations in paddy fields are discussed.

Tobacco MAP kinase phosphatase (NtMKP1) negatively regulates wound response and induced resistance against necrotrophic pathogens and lepidopteran herbivores.

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction pathways in eukaryotic cells. In tobacco, two MAPK, wound-induced protein kinase (WIPK) and salicylic acid (SA)-induced protein kinase (SIPK), are activated by biotic and abiotic stresses. Both WIPK and SIPK positively regulate the biosynthesis of jasmonic acid (JA) or ethylene (ET) while negatively regulating SA accumulation. We showed previously that recombinant tobacco MAPK phosphatase (NtMKP1) protein dephosphorylates and inactivates SIPK in vitro, and overexpression of NtMKP1 repressed wound-induced activation of both SIPK and WIPK. To elucidate the role of NtMKP1 in response to biotic and abiotic stresses, we generated transgenic tobacco plants in which NtMKP1 expression was suppressed. Suppression of NtMKP1 expression resulted in enhanced activation of WIPK and SIPK and production of both JA and ET upon wounding. Wound-induced expression of JA- or ET-inducible genes, basic PR-1 and PI-II, was also significantly enhanced in these plants. Furthermore, NtMKP1-suppressed plants exhibited enhanced resistance against a necrotrophic pathogen, Botrytis cinerea, and lepidopteran herbivores, Mamestra brassicae and Spodoptera litura. These results suggest that NtMKP1 negatively regulates wound response and resistance against both necrotrophic pathogens and herbivorous insects through suppression of JA or ET pathways via inactivation of MAPK.

Identification of sex pheromone components of the box tree pyralid, Glyphodes perspectalis.

Analysis of ovipositor extracts of the box tree pyralid, Glyphodes perspectalis (Lepidoptera: Crambidae), by coupled gas chromatography-electroantennogram detection and gas chromatography yielded three candidate pheromone compounds. Gas chromatography-mass spectrometry, and reaction with dimethyl disulfide (DMDS), identified these compounds as (Z)-11-hexadecenal (Z11-16:Ald), (E)-11-hexadecenal (E11-16:Ald), and (Z)-11-hexadecenol (Z11-16:OH). The ratio of these three compounds in crude extract was 5:1.25:1, and the total amount was approximately 100 ng/female. In laboratory bioassays, Z11-16:Ald alone was attractive to males. In field bioassays, however, Z11-16:Ald alone was not attractive to males, but a mixture of Z11-16:Ald and E11-16:Ald was. The addition of Z11-16:OH to the two aldehydes, significantly reduced attractiveness to male moths in a field trial. From these results, we conclude that the aldehyde compounds comprise the sex pheromone components of G. perspectalis. A rubber septum containing 0.6 mg of the two aldehydes at the natural ratio was an effective lure for monitoring this pest.