Abstract

How plants fulfill their life functions is to a large extend dictated by the presence of cell walls. These cell walls can adopt a wide range of structures, depending on the local functional demands—from stretching in a particular direction to reconciling contradictory requirements. A beautiful example of the latter is found in the primary xylem. Different patterns of local cell wall reinforcements are used at different stages of development, in line with different mechanical requirements. The required anisotropic material properties largely derive from the location and orientation of the constituting cellulose microfibrils. These, in turn are deposited along the cortical microtubule cytoskeleton.

I will describe how we use the banded pattern in protoxylem as a model system for complex cell wall patterns. For this, we use a diversity of modelling approaches involving both cortical microtubules and Rho-of-Plants (ROP) proteins. These deeply conserved small GTPases can establish membrane zones with different properties, leading to local differences in microtubule dynamics. Microtubules, however, do not simply “read out” this pattern. The final pattern arises from the mutual interations of both systems. This work not only helped us understand how these beautiful and functionally important patters are formed, but also brought to light important insights on how the precise distribution of microtubule nucleation plays a critical role in maintaining homogeneous microtubule arrays and, hence, cell wall integrity.

I will also show some stunning pictures from recent field trips to South Africa and the USA to study/hunt for some very special plants: the few known species in the world that display dimorphic enantiostyly, which we use as a model system for the de novo establishment a left-right asymmetry. These plants demonstrate that rich biodiversity we still have in our world is an incredibly valuable resource even for fundamental cell and developmental biology, though challenging and challenged.  

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