Poster: Late and Moved Abstracts
Abs #
1024: Developmental reorientation of cortical microtubules in Allium epidermal cells: a role for cytoplasmic streaming
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Presenter: |
Sainsbury, Frank , fsai2310@mail.usyd.edu.au |
Authors | Sainsbury, Frank (A) Marc, Jan (A) | | Affiliations: |
(A): University of Sydney
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The orientation of interphase cortical microtubules, which is related to the pattern of cellulose microfibril deposition, typically changes from transverse toward longitudinal directions about the end of cell elongation. Although many chemical and physical factors influence microtubule orientation, the cellular mechanism is unknown. We have examined the reorientation of cortical microtubule arrays along the outer epidermal wall in Allium porrum L. leaves using a GFP-MBD microtubule reporter gene or conventional immunofluorescence microscopy. Overnight incubation of leaf segments with cytochalasin D, which blocked cytoplasmic streaming, inhibited the normal developmental reorientation of microtubules to the longitudinal direction. In contrast, incubation with the microtubule-stabilizing drug taxol promoted the developmental reorientation, indicating that this process involves rotation of whole microtubules. Labeling with rhodamine-phalloidin showed that actin cables were oriented predominantly in the longitudinal direction, and transformation with an endoplasmic reticulum-targeted GFP gene revealed longitudinal cytoplasmic streaming near the cell cortex. Observation of GFP-labeled microtubules in living cells showed that cytoplasmic streaming was powerful enough to displace and rotate loose microtubules. Since we found that phospholipase D may link microtubules to the plasma membrane, we incubated leaf segments with the antagonist 1o-butanol. As expected, 1o-butanol promoted the microtubule reorientation, especially in the presence of taxol. We propose that cytoplasmic streaming drives the developmental reorientation of microtubules to the longitudinal direction when the microtubules become released from their anchoring in the cortex as the cells mature.
