ram dixit biology department [email protected]
TRANSCRIPT
Plant Microtubule Arrays
Wasteneys. J Cell Science. 2002
Interphase cortical array
Preprophaseband
Spindleapparatus
Phragmoplast
The cortical microtubule cytoskeleton
• The arrangement of cellulose microfibrils mirrors that of the underlying CMTs
• The CMT array acts as a scaffold that directs the deposition of cell wall material
Microtubules
Cellulose cables
Cortical microtubule orientation is important for its function
Random cortical MT arrangement = Isodiametric cells
Ordered cortical MT arrangement = Polarized cell elongation
Burk and Ye. 2002. Plant Cell
How do cortical microtubules become organized into particular patterns?
Movie of Cortical Microtubules
• Crowded array• Microtubules are dynamic (although global pattern persists over time)• New microtubules are born; some are cut (ignore these events for the following analyses)
Green = microtubule polymerRed = microtubule growing tip (comet)
Extracting information from images
1) Image‐based orientation analysis: How stable is the array orientation regionally and globally?
Input: an image stack of microtubule video framesOutput: The orientation distribution of microtubules in each frame and its change across frames, in the form of:
a) A histogram showing the distribution of # of microtubules by angles, for a given frame– to determine the dominant angle for each frameb) A color bar showing the regional dominant microtubule angle along the X axis (long axis of the cell), for a given frame (divide the cell into 10 sectors)c) An image created by stacking the color bars in (b) over all frames– to represent the regional microtubule orientation dynamics
T = 0 T = 1 T = 2
2) Interactive comet tracking: What is the (absolute) angular orientation of each microtubule? What is the average duration of microtubule growth?
Input: an image stack of comet video frames, and user‐specified location of ONE comet on a start frameOutput: the same comet tracked through subsequent frames until it disappears. As an extension, the user should be able to click on multiple comets and the algorithm can track them simultaneously.
T = 0
T = 1
T = 2
T = 3
T = 4
T = 5
NOTE: Disappearance of comet does not mean that the microtubule is gone, it generally means that the microtubule is shortening (and it can start to re‐grow again)
3) Population‐wide lifespan/orientation analysis
Input: an image stack of comet video frames,Output: the algorithm automatically identifies a collection of comet trails and analyze their average life span (and orientation)NOTE: May not be able to distinguish between multiple microtubules growing at the same orientation (or between multiple growth phases of the same microtubule)