Green leaf volatiles (GLVs) are commonly emitted by green plants, and their production is drastically enhanced when they are under biotic stress. To clarify the ecological function of naturally emitted GLVs, we studied the response of Arabidopsis, whose GLV biosynthesis had been modified, when subjected to herbivory or a pathogenic infection. There was a significant increase in GLV production after herbivory by cabbage white butterfly larvae and pathogen (gray mold) infection in hydroperoxide lyase (HPL) sense Arabidopsis compared with WT controls. The HPL sense modification resulted in the plant being more attractive to the parasitic wasp Cotesia glomerata, leading to higher mortality of the herbivores. The HPL sense modification also resulted in greater inhibition of growth of the fungus. By contrast, HPL antisense Arabidopsis produced fewer GLVs, attracted fewer parasitoids, and was more susceptible to the pathogens than the WT control. These data show that (i) one of the ecological functions of GLV biosynthesis related to resistance against both herbivores and pathogens, and (ii) the genetic modification of GLV biosynthesis could be a unique approach for improving plant resistance against such biotic stresses.Arabidopsis ͉ hydroperoxide lyase ͉ tritrophic interactions ͉ Cotesia glomerata ͉ Botrytis cinerea

Fruit development normally occurs after pollination and fertilization; however, in parthenocarpic plants, the ovary grows into the fruit without pollination and/or fertilization. Parthenocarpy has been recognized as a highly attractive agronomic trait because it could stabilize fruit yield under unfavorable environmental conditions. Although natural parthenocarpic varieties are useful for breeding Solanaceae plants, their use has been limited, and little is known about their molecular and biochemical mechanisms. Here, we report a parthenocarpic eggplant mutant,pad-1, which accumulates high levels of auxin in the ovaries. Map-based cloning showed that the wild-type (WT)Pad-1gene encoded an aminotransferase with similarity toArabidopsis VAS1gene, which is involved in auxin homeostasis. Recombinant Pad-1 protein catalyzed the conversion of indole-3-pyruvic acid (IPyA) to tryptophan (Trp), which is a reverse reaction of auxin biosynthetic enzymes, tryptophan aminotransferases (TAA1/TARs). The RNA level ofPad-1gene increased during ovary development and reached its highest level at anthesis stage in WT. This suggests that the role ofPad-1in WT unpollinated ovary is to prevent overaccumulation of IAA resulting in precocious fruit-set. Furthermore, suppression of the orthologous genes ofPad-1induced parthenocarpic fruit development in tomato and pepper plants. Our results demonstrated that the use ofpad-1genes would be powerful tools to improve fruit production of Solanaceae plants.

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