title: Mutation of Arabidopsis BARD1 causes meristem defects by failing to confine WUSCHEL expression to the organizing center.
abstract: Stem cell fate in the Arabidopsis thaliana shoot apical meristem (SAM) is controlled by WUSCHEL (WUS) and CLAVATA. Here, we examine BARD1 (for BRCA1-associated RING domain 1), which had previously been implicated in DNA repair functions; we find that it also regulates WUS expression. We observed severe SAM defects in the knockout mutant bard1-3. WUS transcripts accumulated >238-fold in bard1-3 compared with the wild type and were located mainly in the outermost cell layers instead of the usual organizing center. A specific WUS promoter region was recognized by nuclear protein extracts obtained from wild-type plants, and this protein-DNA complex was recognized by antibodies against BARD1. The double mutant (wus-1 bard1-3) showed prematurely terminated SAM structures identical to those of wus-1, indicating that BARD1 functions through regulation of WUS. BARD1 overexpression resulted in reduced WUS transcript levels, giving a wus-1-like phenotype. Either full-length BARD1 or a clone that encoded the C-terminal domain (BARD1:C-ter;bard1-3) was sufficient to complement the bard1-3 phenotype, indicating that BARD1 functions through its C-terminal domain. Our data suggest that BARD1 regulates SAM organization and maintenance by limiting WUS expression to the organizing center.
authors.affiliation: National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Han
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Yu-Xian
authors.initials: YX
authors.lastname: Zhu
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D018519:Meristem / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D030821:Plants, Genetically Modified / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C116421:WUSCHEL protein, Arabidopsis