Interaction between autonomous and microtubule guidance systems controls cellulose synthase trajectories Item

The organisation of
cellulose microfibrils is critical for the strength and growth of plant cell
walls. Microtubules have been shown to play
a key role in controlling microfibril organisation by guiding cellulose
synthase complexes.
However, cellulose synthase trajectories can be maintained when
microtubules are removed by drugs, suggesting a separate guidance mechanism is also
at play. By
slowing down microtubule dynamics, we reveal such a mechanism by showing that cellulose
synthase complexes can interact with the trails left by other complexes,
causing them to follow the trails or disappear.
The stability of the trails, together with the sensitivity of their directions
to cellulase treatment, indicates they most likely reflect nascent cellulose
microfibrils. Over many hours, this
autonomous mechanism alone can lead to a change in the dominant orientation of cellulose
synthase trajectories. However, the mechanism can be overridden by the
microtubule guidance system. Our findings
suggest a dual guidance model, in which an autonomous system, involving
interaction between cellulose synthases and microfibrils, can maintain aligned cellulose
synthase trajectories, while a microtubule guidance system allows alignments to
be steered by environmental and developmental cues.