title: ARC1 is an E3 ubiquitin ligase and promotes the ubiquitination of proteins during the rejection of self-incompatible Brassica pollen.
abstract: ARC1 is a novel U-box protein required in the Brassica pistil for the rejection of self-incompatible pollen; it functions downstream of the S receptor kinase (SRK). Here, we show that ARC1 has E3 ubiquitin ligase activity and contains several motifs that influence its subcellular localization. ARC1 can shuttle between the nucleus, cytosol, and proteasome/COP9 signalosome (CSN) when expressed in tobacco BY-2 suspension-cultured cells. However, ARC1 localization to the proteasome/CSN occurs only in the presence of an active SRK. In the pistil, ubiquitinated protein levels increase specifically with incompatible pollinations, but they do not change in ARC1 antisense-suppressed pistils. In addition, inhibition of the proteasomal proteolytic activity disrupts the self-incompatibility response. We propose that ARC1 promotes the ubiquitination and proteasomal degradation of compatibility factors in the pistil, which in turn leads to pollen rejection.
authors.affiliation: Department of Botany, University of Toronto, Toronto, Ontario, Canada M5S 3B2.
authors.forename: Sophia L
authors.initials: SL
authors.lastname: Stone
authors.forename: Erin M
authors.initials: EM
authors.lastname: Anderson
authors.forename: Robert T
authors.initials: RT
authors.lastname: Mullen
authors.forename: Daphne R
authors.initials: DR
authors.lastname: Goring
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001937:Brassica / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D000075686:COP9 Signalosome Complex; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005298:Fertility; D049452:Green Fluorescent Proteins; D008025:Ligases / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011058:Pollen / Q000201:enzymology* / Q000254:growth & development; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000096:biosynthesis
chemical_list: D029681:Arabidopsis Proteins; C445070:CSN6B protein, Arabidopsis; D002352:Carrier Proteins; D008164:Luminescent Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D014452:Ubiquitins; D049452:Green Fluorescent Proteins; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; C079832:S-receptor kinase; D000075686:COP9 Signalosome Complex; D008025:Ligases