Wall-associated kinase 1 (WAK1) is crosslinked in endomembranes, and transport to the cell surface requires correct cell-wall synthesis.
The Arabidopsis thaliana wall-associated kinases (WAKs) bind to pectin with an extracellular domain and also contain a cytoplasmic protein kinase domain. WAKs are required for cell elongation and modulate sugar metabolism. This work shows that in leaf protoplasts a WAK1-GFP fusion protein accumulates in a cytoplasmic compartment that contains pectin. The WAK compartment contains markers for the Golgi, the site of pectin synthesis. The migration of WAK1-GFP to the cell surface is far slower than that of a cell surface receptor not associated with the cell wall, is influenced by the presence of fucose side chains on one or more unidentified molecules that might include pectin, and is dependent upon cellulose synthesis on the plasma membrane. WAK is crosslinked into a detergent-insoluble complex within the cytoplasmic compartment before it appears on the cell surface, and this is independent of fucose modification or cellulose synthesis. Thus, the assembly and crosslinking of WAKs may begin at an early stage within a cytoplasmic compartment rather than in the cell wall itself, and is coordinated with synthesis of surface cellulose.
Kohorn
Bruce D
BD
Department of Biology, Bowdoin College, Brunswick, ME 04011, USA. bkohom@bowdoin.edu
Kobayashi
Masaru
M
Johansen
Sue
S
Friedman
Henry Perry
HP
Fischer
Andy
A
Byers
Nicole
N
D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002482:Cellulose / Q000096:biosynthesis; D003001:Cloning, Molecular; D006056:Golgi Apparatus / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism*; D010368:Pectins / Q000096:biosynthesis / Q000378:metabolism; D011494:Protein Kinases / Q000096:biosynthesis / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D011523:Protoplasts / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D029681:Arabidopsis Proteins; D015415:Biomarkers; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C476110:mur1 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D010368:Pectins; D002482:Cellulose; D011494:Protein Kinases; C101093:WAK1 protein, Arabidopsis