title: Suppression of root nodule formation by artificial expression of the TrEnodDR1 (coat protein of White clover cryptic virus 1) gene in Lotus japonicus.
abstract: TrEnodDR1 (Trifolium repens early nodulin downregulation 1) encodes a coat protein of White clover cryptic virus 1. Its expression in white clover was down-regulated at the time when root nodules formed. We surmised that its artificial expression would interfere with root nodulation. Therefore, we investigated the effects of its artificial expression on the growth and root nodulation of Lotus japonicus (a model legume). Transformants were prepared by Agrobacterium spp.-mediated transformation. The growth of transformants was reduced and the number of root nodules per unit root length was greatly decreased relative to control. The concentration of endogenous abscisic acid (ABA), which controls nodulation, increased in plants containing TrEnodDR1. These phenotypes clearly were canceled by treatment with abamine, a specific inhibitor of ABA biosynthesis. The increase in endogenous ABA concentration explained the reduced stomatal aperture and the deformation of root hairs in response to inoculation of transgenic L. japonicus with Mesorhizobium loti. Transcriptome comparison between TrEnodDR1 transformants and control plants showed clearly enhanced expression levels of various defense response genes in transformants. These findings suggest that TrEnodDR1 suppresses nodulation by increasing the endogenous ABA concentration, perhaps by activating the plant's innate immune response. This is the first report of the suppression of nodulation by the artificial expression of a virus coat protein gene.
authors.affiliation: Graduate School of Science and Technology, Kagoshima University, Japan.
authors.forename: Mitsumi
authors.initials: M
authors.lastname: Nakatsukasa-Akune
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamashita
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Shimoda
authors.forename: Toshiki
authors.initials: T
authors.lastname: Uchiumi
authors.forename: Mikiko
authors.initials: M
authors.lastname: Abe
authors.forename: Toshio
authors.initials: T
authors.lastname: Aoki
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kamizawa
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ayabe
authors.forename: Shiro
authors.initials: S
authors.lastname: Higashi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Suzuki
mesh_terms: D001483:Base Sequence; D036022:Capsid Proteins / Q000235:genetics*; D017931:DNA Primers; D017343:Genes, Plant; D000070116:Lotus / Q000235:genetics*; D018517:Plant Roots / Q000254:growth & development*; D010942:Plant Viruses / Q000235:genetics*; D030821:Plants, Genetically Modified; D014170:Transformation, Genetic
chemical_list: D036022:Capsid Proteins; D017931:DNA Primers