Signals originating from both hormones and light combine to direct plant growth patterns that make efficient use of the surrounding environmental resources. The overlap in developmental responses directed by cytokinin and light suggests a molecular connection between these pathways. My preliminary data show that lesions in the cytokinin receptors can affect light response and conversely that mutation of the light receptors can affect cytokinin response. This proposal describes experiments that will examine the molecular mechanisms behind integrated cytokinin and light action in plants. Each of these signaling pathways has been examined separately but little is known regarding how these pathways interact. Using existing genetic tools we aim to uncover the roles played by components of both the light and cytokinin signaling machinery in cross-talk between these pathways. Specifically, we propose to (1) examine the light-cytokinin interaction by genetic analysis of cytokinin and photoreceptor mutants using physiological response assays; (2) test the potential role of cytokinin induced genes in stabilization of the active form of phytochrome and identify new factors potentially involved in cross-talk between the light and cytokinin signaling pathways; and (3) explore a potential connection between cytokinin and brassinosteroid mediated by a cytokinin-induced steroid-sulfotransferase. The proposed experiments will enhance our knowledge of the cytokinin signaling pathway and will address the mechanism by which light and cytokinin interact to regulate seedling morphology. This will be a first step in furthering our understanding of the signaling networks that control seedling development.
