The ROOT HAIRLESS 1 gene encodes a nuclear protein required for root hair initiation in Arabidopsis.
The epidermis of Arabidopsis wild-type primary roots, in which some cells grow hairs and others remain hairless in a position-dependent manner, has become an established model system to study cell differentiation. Here we present a molecular analysis of the RHL1 (ROOT HAIRLESS 1) gene that, if mutated, prevents the formation of hairs on primary roots and causes a seedling lethal phenotype. We have cloned the RHL1 gene by use of a T-DNA-tagged mutant and found that it encodes a protein that appears to be plant specific. The predicted RHL1 gene product is a small hydrophilic protein (38.9 kD) containing putative nuclear localization signals and shows no significant homology to any known amino acid sequence. We demonstrate that a 78-amino-acid sequence at its amino terminus is capable of directing an RHL1-GFP fusion protein to the nucleus. The RHL1 transcript is present throughout the wild-type plant and in suspension culture cells, but in very low amounts, suggesting a regulatory function for the RHL1 protein. Structural evidence suggests a role for the RHL1 gene product in the nucleolus. We have examined the genetic relationship between RHL1 and GL2, an inhibitor of root hair initiation in non-hair cells. Our molecular and genetic data with double mutants, together with the expression analysis of a GL2 promoter-GUS reporter gene construct, indicate that the RHL1 gene acts independently of GL2.
Schneider
K
K
Department of Cell Biology, John Innes Centre, Colney, Norwich, NR4 7UH, UK. kschneid@mpiz-koeln.mpg.de
Mathur
J
J
Boudonck
K
K
Wells
B
B
Dolan
L
L
Roberts
K
K
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D017343:Genes, Plant; D018398:Homeodomain Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D018517:Plant Roots / Q000235:genetics* / Q000254:growth & development*; D017421:Sequence Analysis; D013347:Subcellular Fractions / Q000378:metabolism; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C089991:GL2 protein, Arabidopsis; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; C113289:RHL1 protein, Arabidopsis