title: Adaptive significance of gall formation for a gall-inducing aphids on Japanese elm trees.
abstract: Insect galls are abnormal plant tissues induced by external stimuli from parasitizing insects. It has been suggested that the stimuli include phytohormones such as auxin and cytokinins produced by the insects. In our study on the role of hormones in gall induction by the aphid Tetraneura nigriabdominalis, it was found that feedback regulation related to auxin and cytokinin activity is absent in gall tissues, even though the aphids contain higher concentrations of those phytohormones than do plant tissues. Moreover, jasmonic acid signaling appears to be compromised in gall tissue, and consequently, the production of volatile organic compounds, which are a typical defense response of host plants to herbivory, is diminished. These findings suggest that these traits of the gall tissue benefit aphids, because the gall tissue is highly sensitive to auxin and cytokinin, which induce and maintain it. The induced defenses against aphid feeding are also compromised. The abnormal responsiveness to phytohormones is regarded as a new type of extended phenotype of gall-inducing insects.
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Takei
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawai
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Morifumi
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan. Electronic address: ayoshi@mx.ibaraki.ac.jp.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001042:Aphids / Q000502:physiology*; D003517:Cyclopentanes / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism; D006790:Host-Parasite Interactions; D007210:Indoleacetic Acids / Q000378:metabolism; D054883:Oxylipins / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism / Q000469:parasitology; D010941:Plant Tumors / Q000469:parasitology*; D034403:Ulmus / Q000378:metabolism / Q000469:parasitology*
chemical_list: D003517:Cyclopentanes; D003583:Cytokinins; D007210:Indoleacetic Acids; D054883:Oxylipins; D010937:Plant Growth Regulators; C011006:jasmonic acid
keywords: Adaptive significance; Auxin; Gall; Jasmonic acid; Tetraneura nigriabdominalis; Ulmus davidiana