title: The bifunctional abiotic stress signalling regulator and endogenous RNA silencing suppressor FIERY1 is required for lateral root formation.
abstract: The Arabidopsis FIERY1 (FRY1) locus was originally identified as a negative regulator of stress-responsive gene expression and later shown to be required for suppression of RNA silencing. In this study we discovered that the FRY1 locus also regulates lateral root formation. Compared with the wild type, fry1 mutant seedlings generated significantly fewer lateral roots under normal growth conditions and also exhibited a dramatically reduced sensitivity to auxin in inducing lateral root initiation. Using transgenic plants that overexpress a yeast homolog of FRY1 that possesses only the 3', 5'-bisphosphate nucleotidase activity but not the inositol 1-phosphatase activity, we demonstrated that the lateral root phenotypes in fry1 result from loss of the nucleotidase activity. Furthermore, a T-DNA insertion mutant of another RNA silencing suppressor, XRN4 (but not XRN2 or XRN3), which is an exoribonuclease that is inhibited by the substrate of the FRY1 3', 5'-bisphosphate nucleotidase, exhibits similar lateral root defects. Although fry1 and xrn4 exhibited reduced sensitivity to ethylene, our experiments demonstrated that restoration of ethylene sensitivity in the fry1 mutant is not sufficient to rescue the lateral root phenotypes of fry1. Our results indicate that RNA silencing modulated by FRY1 and XRN4 plays an important role in shaping root architecture.
authors.affiliation: Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Liming
authors.initials: L
authors.lastname: Xiong
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D005030:Ethylenes / Q000378:metabolism; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D009708:Nucleotidases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010744:Phosphoric Monoester Hydrolases; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development*; D034622:RNA Interference; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D005030:Ethylenes; D007210:Indoleacetic Acids; D010940:Plant Proteins; C418137:Xrn1 protein, plant; D000244:Adenosine Diphosphate; C036216:ethylene; C010840:adenosine 3'-phosphate-5'-phosphate; D005095:Exoribonucleases; D009708:Nucleotidases; D010744:Phosphoric Monoester Hydrolases; C053087:inositol-1,4-bisphosphate 1-phosphatase; C053354:bisphosphoadenylate 3'-nucleotidase