A long standing hypothesis is that the cortical microtubule array guides plant cell morphogensis by directing the orientation of cellulose deposition in the cell wall. This idea has been supported by many experiments, including disruption of the cortical array by drug treatment or mutation, and assay of cellulose orientation by polarization microscopy or EM techniques, such as FESEM. However, these techniques do not allow the dynamic relationship between cellulose synthase complexes and the cytoskleton to be evaluated, and they have not satifactorily revealed the relationship of individual components of the cortical cytoskeleton to the deposition individual microfibrils. To address these questions and to test the microfibril guidance hypothesis, we created a functional fluorescent protein fusion to CESA6, a catalytic subunit of the cellulose synthase complex, and imaged this tagged protein in growing Arabidopsis cells. Imaging of tagged protein motility provides an assay for the orientation and rate of cellulose biosynthesis at the level of single biosynthetic complexes. |
