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Ubiquitin–proteasome‐mediated degradation of S ‐ RN ase in a solanaceous cross‐compatibility reaction
Author(s) -
Entani Tetsuyuki,
Kubo Kenichi,
Isogai Shin,
Fukao Yoichiro,
Shirakawa Masahiro,
Isogai Akira,
Takayama Seiji
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12528
Subject(s) - f box protein , pollen , biology , proteasome , rnase p , ribonuclease , ubiquitin , genetics , protein degradation , biochemistry , ubiquitin ligase , gene , botany , rna
Summary Many plants have a self‐incompatibility ( SI ) system in which the rejection of self‐pollen is determined by multiple haplotypes at a single locus, termed S . In the Solanaceae, each haplotype encodes a single ribonuclease ( S ‐ RN ase) and multiple S ‐locus F ‐box proteins ( SLF s), which function as the pistil and pollen SI determinants, respectively. S‐ RN ase is cytotoxic to self‐pollen, whereas SLF s are thought to collaboratively recognize non‐self S‐ RN ases in cross‐pollen and detoxify them via the ubiquitination pathway. However, the actual mechanism of detoxification remains unknown. Here we isolate the components of a SCF SLF ( SCF = SKP 1‐ CUL 1‐ F ‐box‐ RBX 1) from P etunia pollen. The SCF SLF polyubiquitinates a subset of non‐self S ‐ RN ases in vitro . The polyubiquitinated S ‐ RN ases are degraded in the pollen extract, which is attenuated by a proteasome inhibitor. Our findings suggest that multiple SCF SLF complexes in cross‐pollen polyubiquitinate non‐self S ‐ RN ases, resulting in their degradation by the proteasome.