The decision to grow or to stop growing is fundamental for plant survival. Small organic molecules called phytohormones play an important role in growth regulation. Significant progress has been made in identification and characterization of regulatory biosynthesis pathway and signaling components of various phytohormones. However our knowledge of how different hormones regulate growth in time and space and how they are coordinated remains rudimentary. Recent findings have revised the dogma that phytohormones are acting in all cells of the plant body to regulate its growth. Thus, it has been demonstrated that phytohormones act locally and in a particular cell type to affect growth of the entire organ. An exciting recent finding in this regard is that perception of the polyhydroxylated steroids called brassinosteroids (BRs) in epidermal cells are sufficient to control the growth of all above-ground organs in the model plant Arabidopsis. This suggests that signal/s, yet unknown, are used to coordinate growth between the epidermis and inner cell-layers in the plant. Therefore, my proposal aims to address the following questions: what is the spatio-temporal regulation of BR signal transduction during growth and to what extent cell-cell communication is involved, what is the molecular basis for cell-cell communication and how mechanical and phytohormone signals are integrated to control final size. To answer these questions my lab will use advanced genomic approaches including tissue specific short-read sequencing of hormonal regulated mRNA and high-throughput chemical genetic screens. Furthermore, my lab will develop biosensors for hormonal readout at the cellular level which will be combined with cell biology and genetic tools.
Taken together, these studies should lead to a significant progress in our understanding of how simultaneous growth of an organ is orchestrated and how local signals in cells and tissues are integrated to control this process.
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