Mechanosensitive Channels and Organelle Morphology

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While it has long been appreciated that mechanical stimuli like gravity, touch, and osmotic pressure are important regulators of plant growth and development, the molecular mechanisms by which plant cells perceive mechanical force is not yet understood. In animal and bacterial systems, mechanosensitive (MS) ion channels mediate the perception of many mechanical stimuli. In plants, a family of proteins related to the bacterial MS channel MscS are implicated in mechanosensory signal transduction. In the model flowering plant Arabidopsis thaliana, two members of this MscS-Like (MSL) family are targeted to the poles of chloroplasts where they control plastid shape and size. How plastids (or organelles in general) take their shape is an area of recent excitement, and the role that mechanosensory systems might play in such a process has not yet been addressed. The objectives of this project are to: 1) further delineate how and why MSL2 and MSL3 are localized to the poles of plastids; 2) address the evolutionary history of MscS-Like proteins by determining their function in Synechocystis sp. PC6803, cyanobacteria that share a common ancestor with plant chloroplasts, and 3) develop nongreen plastids in Arabidopsis thaliana as a model system for studying organelle morphology control. These studies address two general goals: (i) to further our understanding of plant cell biology and how plants use MS ion channels to sense and respond to important stimuli; and (ii) to advance our knowledge of the basic principles of mechanotransduction and organelle shape determination.Broader impacts. The PI has been involved in women's advocacy for many years, and is strongly committed to expanding opportunities for women and minorities in STEM fields. The Undergraduate Plastid Project will be developed as a platform for undergraduate research, and will be integrated into an existing Pathway for undergraduate studies in imaging technologies at Washington University. A high school teacher-intern will participate in this research program during two consecutive summers, develop innovative curricula, and ultimately benefit the students at his or her school. Finally, a Washington University doctoral student will be provided an important training environment.