CAREER: Asymmetry of microtubule dynamics in plant cytokinesis: the role of microtubule-nucleating protein MACET1

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The ability of plants to transition successfully from a marine to land environment required evolutionary advances in cellular activity, including a novel mechanism of cell division. The ability to understand, predict, and regulate this mechanism could have broad scientific and economic impacts. For example, the vascular cambium influences overall plant growth and is produced through the division of unusually large precursor cells. These divisions are known to rely on the expansion of a plant-specific structure termed the phragmoplast; however, a detailed understanding of phragmoplast expansion is lacking. This CAREER project will fill this knowledge gap using a combination of laboratory experiments and mathematical modeling and will provide foundational knowledge for increasing the rate of cell division, and subsequently wood yield, in trees that are grown for industrial biomass. Although the need for timber has grown by 36% over the past 25 years, forestland continues to shrink and developed countries depend heavily on imports from tropical zones. Bio-engineered trees with faster growth rates has the potential to increase production of timber as a renewable material in the US with additional benefits coming through increased sequestration of carbon dioxide. Cutting-edge concepts of this research will be integrated into an educational program for students that attend regional Native American high schools and nearby Lewis Clark State College (ID) and Walla Walla Community College (WA). The program will introduce the importance of plants as a natural resource; promote STEM education; and encourage careers in STEM-related professions. The expansion of the phragmoplast centrifugally is critically dependent on the dynamic and asymmetrical behavior of microtubules. The PI has identified the protein MACET, which is specific to embryophytes, promotes microtubule nucleation, exhibits asymmetrical localization in the phragmoplast, and facilitates phragmoplast expansion. This discovery provides an exciting entry point for further studies to unravel the regulation of phragmoplast asymmetry. In this CAREER project, the PI will use a combination of approaches in genetics, biochemistry, and cell biology to characterize MACET function(s) in cytokinesis. In addition, the role of MACET in asymmetrical microtubule dynamics in the phragmoplast will be determined using quantitative live cell imaging and mathematical modeling. These approaches will advance our understanding of the basic rules that govern the construction of highly complex, but transient intracellular structures. As organisms rely on mechanisms that facilitate the irregular distribution of matter and energy to meet biological needs, understanding phragmoplast asymmetry would unravel another facet of the governing principles of life.