Suppression of root nodule formation by artificial expression of the TrEnodDR1 (coat protein of White clover cryptic virus 1) gene in Lotus japonicus.
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.
Nakatsukasa-Akune
Mitsumi
M
Graduate School of Science and Technology, Kagoshima University, Japan.
Yamashita
Kenji
K
Shimoda
Yoshikazu
Y
Uchiumi
Toshiki
T
Abe
Mikiko
M
Aoki
Toshio
T
Kamizawa
Ayumi
A
Ayabe
Shin-ichi
S
Higashi
Shiro
S
Suzuki
Akihiro
A
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
D036022:Capsid Proteins; D017931:DNA Primers