Plant responses to environmental cues: Novel roles for microtubule plus-end binding proteins.

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Plants are sessile and cannot change locations when conditions become unfavorable. Instead they respond to environmental stimuli by modifying their growth. Plant growth responses involve changes at the cellular level that, in turn, affect the size and shape of the plant and the placement of leaves, stems, roots, and flowers. Microtubules play key roles in many of the relevant cellular processes. Despite their central role, little is known about how information is relayed through microtubules to alter growth. The long term goal of my research program is to determine how information is transmitted to and from microtubules to effect changes in plant growth and development. Towards this goal, we are studying +TIPs, a large and diverse group of microtubule associated proteins that bind to the rapidly growing "plus" ends of microtubules. +TIPS are prime candidates for molecules that could relay information between microtubules and other subcellular components in plants. In particular, members of the END BINDING 1 (EB1) family have emerged as core regulatory +TIPs in animal and fungal cells, since they bind and recruit many other proteins to microtubule ends. We discovered that EB1 regulates developmental processes in plants; the proteins suppress root responses to mechanical cues, affect subcellular architecture, and have roles in root hairs. These discoveries are consistent with the hypothesis that EB1 relays information between microtubules and other components in plant cells. The research proposed here aims to elucidate the functions of EB1 in root hairs and in roots responding to mechanical cues and to discover novel proteins involved in the relay of information to and from microtubules. Root responses to mechanical cues play key roles in plant fitness and affect productivity in crop plants because they determine how effectively the root system can penetrate through the soil in search of water and nutrients. Root hairs are also paramount for survival and fitness in plants, since they provide the surfaces across which water and nutrients are absorbed. The knowledge that is gained from these studies will impact the development of strategies aimed at improving productivity in crop plants.