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Dissecting dynamic endosomal recycling in plants.


A National Science foundation ChemGen Interdisciplinary Graduate Research and Training (ChemGen IGERT) program-sponsored study has led to the identification of over 350 synthetic compounds that disrupt endomembrane trafficking. This project is led by Distinguished Professor of Plant Cell Biology Natasha Raikhel and Associate Research Plant Cell Biologist Glenn Hicks of the Institute of Integrative Genome Biology. This study has been a collaborative effort with Eugenia Russinova and Jiri Friml, both of the Ghent University. ChemGen IGERT fellow Michelle Brown participated in the screening of over 46,000 compounds to identify the 365 protein trafficking disruptors in tobacco pollen. Over a third of the 365 compounds disrupted the localization of three well-defined plasma membrane proteins known to cycle in Arabidopsis. Under the supervision of a bioinformaticist, Associate Professor Thomas Girke, an analysis of compound traits was performed to identify categories of compounds that cause specific mis-localization effects. Due to the variation in compound structures observed in the same phenotype classes. The analysis determined that numerous protein inhibitions cause similar phenotypic effects, indicating a large number of potential targets within the membrane cycling pathway.

This compound subset library was then tested to determine how many of these compounds affect gravity response in Arabidopsis, due to the known relationship between endomembrane trafficking and gravitropic response. Sixteen compounds were found that highly disrupt the ability to respond to a change in gravity direction. One of these compounds, Endosidin2, was found to specifically inhibit endosomal recycling in a more specific manner than the only other known recycling inhibitor, Brefeldin A. Endosidin2 (ES2) was also able to inhibit protein recycling without affecting other internal compartments as manifested by Brefeldin A. ES2 provides a new tool to investigate the highly dynamic and transient processes of protein cycling. ES2 will also be useful in defining the part that endosomal recycling plays in hormone perception and response, as two important hormones, auxin and brassinsteroids, have already been shown to be affected by ES2.

Address Goals

The vacuole is the largest member of the endomembrane system and Sortin1 demonstrates a greater diversity for vacuolar transporters which translates to a better understating for plant viability and development. This research can be translated to crop species to increase production in sub-optimal conditions.