A cross-species study of the effects of agrochemicals on microtubule dynamics through the development of new live imaging probes

Global demand for food is growing; current projections indicate that we will need 60% more food in 2050. This puts increasing pressure on a food production system that already has to cope with reduced natural resources and the results of climate change. To help us meet the growing demand for food, it is vital that we increase the efficiency with which we grow crops. An important method to increase crop productivity is the careful use of agrochemicals. Indeed, the use of such agrochemicals has provided significant advances in crop production and food provision. It is therefore essential that we continue to develop better and safer agrochemicals that will help us make the best use of our limited natural resources.
The microtubule cytoskeleton is an important biological target for the development of new herbicides and fungicides. Microtubules are required for a wide range of cellular processes, from cell division to cellular transport, making them an important target for agrochemical compounds. However, because microtubules are so well conserved across species, a major challenge is to identify compounds that are toxic to the targeted pest species (plants or fungi) without affecting crops, humans and other non-target species. It is therefore vital that we have a better understanding of the differences in the responses to microtubule perturbators in all of these populations. To this end, we need to develop tools that can allow a more detailed assessment of microtubule function across a range of organisms. This information will contribute to early decision-making in the development and design of new agrochemicals.
Microtubules are inherently dynamic structures: being constantly remodeled through fluctuations in polymerization and depolymerisation. This dynamic behavior is crucial for many of the cellular functions of microtubules; for example, during cell division the microtubules of the mitotic spindle search for chromosomes by probing the cytoplasm through rapid cycles of polymerization and depolymerization. The suppression of these dynamics is also key for other microtubule functions in the cell; indeed the stabilization of microtubules by specific microtubule associated proteins (MAPs) is vital for determining the polarity of a cell. Microtubule-targeting agrochemicals generally function by disrupting the fine balance of microtubule dynamics in a cell. Because only a subtle change in dynamics can have a profound effect on the cell, it is important that we understand in detail how a compound affects the polymerization, depolymerization and stabilization of microtubules and compare this across both target and non-target organisms. To do this, it is crucial that we are able to visualize and measure microtubule dynamics in living cells, tissues and embryos, rather than dead, fixed tissues.

Our project aims to determine in detail the effect of specific agrochemicals on microtubule dynamics in plant and animal cells at the level of the single cell, tissue and whole embryo. Importantly, this will involve the development of new probes for the imaging of microtubules in living cells. These new probes will overcome current limitations with existing probes, which give can give diffuse or uneven staining of microtubules or affect microtubule dynamics. Understanding the biological differences of microtubule perturbers across species at both the level of the cell and whole organism will provide important insights into potential adverse effects of these compounds. This will ultimately aid decision-making and the progression of compounds through the Research and Development pipeline and consequently impact on both the speed to market and the likely success of a compound.

4. Compare the MT responses found in (3) with those seen in the target species of the selected
agrochemicals.