A kinesin-like protein is essential for oriented deposition of cellulose microfibrils and cell wall strength.
Cortical microtubules have long been hypothesized to regulate the oriented deposition of cellulose microfibrils. However, the molecular mechanisms of how microtubules direct the orientation of cellulose microfibril deposition are not known. We have used fibers in the inflorescence stems of Arabidopsis to study secondary wall deposition and cell wall strength and found a fragile fiber (fra1) mutant with a dramatic reduction in the mechanical strength of fibers. The fra1 mutation did not cause any defects in cell wall composition, secondary wall thickening, or cortical microtubule organization in fiber cells. An apparent alteration was found in the orientation of cellulose microfibrils in fra1 fiber walls, indicating that the reduced mechanical strength of fra1 fibers probably was attributable to altered cellulose microfibril deposition. The FRA1 gene was cloned and found to encode a kinesin-like protein with an N-terminal microtubule binding motor domain. The FRA1 protein was shown to be concentrated around the periphery of the cytoplasm but absent in the nucleus. Based on these findings, we propose that the FRA1 kinesin-like protein is involved in the microtubule control of cellulose microfibril order.
Zhong
Ruiqin
R
Department of Plant Biology, University of Georgia, Athens, Georgia 30602, USA.
Burk
David H
DH
Morrison
W Herbert
WH
Ye
Zheng-Hua
ZH
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D002482:Cellulose / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D016547:Kinesins / Q000235:genetics* / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013314:Stress, Mechanical
D029681:Arabidopsis Proteins; C472140:FRA1 protein, Arabidopsis; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D002482:Cellulose; D016547:Kinesins