AtSGP1, AtSGP2 and MAP4K alpha are nucleolar plant proteins that can complement fission yeast mutants lacking a functional SIN pathway.
In the fission yeast Schizosaccharomyces pombe, the onset of septum formation is signalled via the septation initiation network (SIN) involving several protein kinases and a GTPase. Arabidopsis thaliana and Brassica napus proteins homologous to fission yeast spg1p (AtSGP1, AtSGP2), cdc7p (AtMAP3K epsilon 1, AtMAP3K epsilon 2, BnMAP3K epsilon 1) and sid1p (AtMAP4K alpha 1, AtMAP4K alpha 2, BnMAP4K alpha 2) exhibit a significant similarity. The plant proteins AtSGP1/2 and BnMAP4K alpha 2 are able to complement the S. pombe mutant proteins spg1-B8 and sid1-239, respectively and to induce mutisepta when overexpressed in wild-type yeast. Yeast two-hybrid assays demonstrated interactions both between plant proteins and between plant and yeast proteins of the SIN pathway. However, the primary structure of the proteins as well as the partial complementation of yeast mutants indicates that plant homologous proteins and their yeast counterparts have diverged during evolution. Real-time RT-PCR studies demonstrated plant SIN-related gene expression in all organs tested and a co-expression pattern during the cell cycle, with a higher accumulation at G(2)-M. During interphase, the plant SIN-related proteins were found to co-localise predominantly in the nucleolus of the plant cells, as shown by fusions to green fluorescent protein. These data suggest the existence of a plant SIN-related pathway.
Institut de Biotechnologie des Plantes, UMR 8618, Bâtiment 630, Université de Paris-Sud, 91405 Orsay Cedex, France. champion@rulbim.leidenuniv.nl
Antony
A
Champion
Stefan
S
Jouannic
Stéfanie
S
Guillon
Keithanne
K
Mockaitis
Andrea
A
Krapp
Alain
A
Picaud
Viesturs
V
Simanis
Martin
M
Kreis
Yves
Y
Henry
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D029688:Brassica napus / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D008938:Mitosis; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction / Q000235:genetics
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D029702:Schizosaccharomyces pombe Proteins; D011494:Protein Kinases; C117482:MAP4Kalpha1 protein, Brassica napus; C117488:MAP4Kalpha2 protein, Brassica napus; C409036:Sid1 kinase; C489406:cdc7 protein, S pombe; D017346:Protein Serine-Threonine Kinases; C435708:MAP3Kepsilon1 protein, Arabidopsis