| Summary: | The dynamics of root plastids is a little-researched field, with the exception of the statolith in the gravitropic response. Working with Arabidopsis thaliana, this research aims to broaden our knowledge of the cell biology of root plastids in both the columella and the rest of the root.
Root gravitropism relies upon the perception of a signal transduced from starch-filled amyloplasts in the columella cells of the root tip. A new statolith phenotype for the starchless mutant pgm-1 is described, exhibiting highly dynamic, pleomorphic statoliths. This phenotype calls into question the mechanism by which the cell perceives the gravitropic signal. The effects of latrunculin-B on the organisation of the actin cytoskeleton and the graviresponse of the root are also called in to doubt, as confounding factors historically confuse these experiments. Using the FlowCell, an in-house microfluidics device, the high-speed, actin-dependent dynamics of root plastids are described. Root plastids are observed to reach speeds of up almost 16µm/s in the stele of the root, much faster than any other plastid forms. To investigate how root plastids maintain an even distribution through the cell, known plastid division mutants are used to reduce root plastid numbers. These show dramatic changes in root plastid morphology, with some mutants forming network-like plastid structures. This works concludes that root plastids are highly dynamic organelles, capable of adopting a wide range of morphologies and behaviours to adapt to changes in their cellular environment.
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