title: Nitrate inhibits soybean nodulation by regulating expression of CLE genes.
abstract: Nitrogen compounds such as nitrate act as a potential inhibitor for legume nodulation. In this study, we isolated a new CLE gene, GmNIC2, from nitrate-treated roots, which shares high sequence homology with nitrate-induced CLE gene GmNIC1. Similar to GmNIC1, the expression level of GmNIC2 was not significantly altered in roots by rhizobial inoculation and was much higher in young nodules than in roots. In addition, overexpression of GmNIC2 led to similar nodulation inhibition of transgenic hairy roots to that of GmNIC1, which occurred in GmNARK-dependent manner and at the local level. By analyzing GmNARK loss-of-function mutant, SS2-2, it was found that expression levels of GmNIC1 and GmNIC2 in the SS2-2 roots were lower than in the wild type (WT) roots in response to nitrate. In contrast to GmNIC1 and GmNIC2, expressions of GmRIC1 and GmRIC2 genes that are related to the autoregulation of nodulation (AON) were strongly suppressed both of the soybeans during all periods of nitrate treatment and even were not induced by additional inoculation with rhizobia. Taken together, the results of this study suggest that GmNIC2, as an active homologous gene located in chromosome 13, acts locally to suppress nodulation, like GmNIC1, and nitrate inhibition of nodulation is led by fine-tuned regulation of both nitrate-induced CLEs and rhizobia-induced CLEs.
authors.affiliation: Department of Crop Science and Biotechnology, Dankook University, San 29 Anseodong, Cheonan, Chungnam 330-714, Republic of Korea; Department of Life Science (BK21 Program), Chung-Ang University, Seoul 157-756, Republic of Korea.
authors.forename: Chae Woo
authors.initials: CW
authors.lastname: Lim
authors.affiliation: Department of Crop Science and Biotechnology, Dankook University, San 29 Anseodong, Cheonan, Chungnam 330-714, Republic of Korea.
authors.forename: Young Woo
authors.initials: YW
authors.lastname: Lee
authors.affiliation: Department of Life Science (BK21 Program), Chung-Ang University, Seoul 157-756, Republic of Korea.
authors.forename: Sung Chul
authors.initials: SC
authors.lastname: Lee
authors.affiliation: Department of Crop Science and Biotechnology, Dankook University, San 29 Anseodong, Cheonan, Chungnam 330-714, Republic of Korea. Electronic address: sfeho@dankook.ac.kr.
authors.forename: Cheol Ho
authors.initials: CH
authors.lastname: Hwang
mesh_terms: D000595:Amino Acid Sequence; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant; D008969:Molecular Sequence Data; D009566:Nitrates / Q000494:pharmacology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation / Q000187:drug effects / Q000235:genetics*; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics; D012231:Rhizobium / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013025:Glycine max / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*
chemical_list: D009566:Nitrates; D016376:Oligonucleotides, Antisense; D010940:Plant Proteins
keywords: CLE; Nitrate; Nodulation; SS2-2; Supernodulation