UC Riverside

The process of growth in plants is driven by the shoot apical meristem (SAM) which is in turn driven by a signaling network centered around the transcription factor WUSCHEL (WUS). The interaction between WUS and its target genes has a key role in determining the structure of the SAM and fate of its stem cells, as well as how it responds and adapts to its environment. The interplay between WUS and a limited number of other targets such as the gene encoding the peptide CLAVATA3 (CLV3) has been outlined on a basic level through previous studies. However, much work remains to gather more detailed information, develop quantitative molecular explanations for the observed gene expression behaviors, generalize the biology to encompass the broad range of WUS targets, and potentially identify similar regulatory systems elsewhere in plants and other organisms. This study uses a multidisciplinary approach combining experimental and computational techniques to proceed toward these objectives through a number of different avenues. The nature of the cis-regulatory module (CRM) through which CLV3 interacts with WUS was examined showing that individual cis-elements of the CRM behave distinctly when they are working alone compared to when they are working together. This also provided molecular details about the concentration dependent mechanism where the CRM coordinated a nonlinear response to WUS. A computational simulation of the meristem network was tested and data is being gathered on how the resetting of the CLV3 expression gradient to the outer meristem occurs on a molecular level in CLV3 complementation assays. Surveying the CLV3 epigenome revealed a landscape of binding clusters and chromatin looping within the gene and at its ends. This and motif analysis, showed that other targets may share similar features. Imaging studies revealed tissue level dynamics, backing up previously hypothesized mechanisms relating expression to monomeric and multimeric WUS and how it not only regulates but is regulated in turn by a network of interactors.