Molecular genetic of Plant hormone signaling

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Summary: Plant hormones are a collection of small structurally unrelated molecules that have profound effects on plant growth and development. Over the past decade, exciting advances have been made to define core-signaling pathways for many hormones. Now plant hormone biology is entering a challenging period of understanding how the information conveyed by these small molecules is turned into cellular responses. Furthermore, we are also entering a stage where information from experimental models needs to be translated to important crops. My research program investigates the fundamental mechanisms of two plant hormones, abscisic acid (ABA) and strigolactones (SLs) with respect to germination and early seedling growth. Here, I propose to use the cutting edge tools of systems and chemical biology to link these hormones to plant growth and development networks in novel ways both at a fundamental level and for biotechnological application. Project 1: ABA is a long studied hormone that mediates an assortment of developmental responses across a variety of kingdoms. In plants, ABA is a key player in germination and leaf water relations. At a transcriptional level, ABA regulates over a third of a plant’s genome. Thus, the elucidation of the transcription factors (TFs) that are controlled by ABA is critical to linking this hormone to the numerous developmental processes that it controls. In other model systems, controlled activation of TFs followed by monitoring of global gene expression has been a fruitful strategy in assigning functionality in vivo without any prior biological knowledge. Building on previous protein network studies, we will use systems approaches in the model Arabidopsis to develop the first cell type specific ABA regulated TF network. The approach should be adaptable to other plant hormone systems, which have complicated transcriptional outputs. Project 2: SLs form a relatively new class of hormones that are used as a germination cue by parasitic plants of the Striga genera to coordinate their growth with a host’s life cycle. Once crops are planted, their roots exude SLs, which act to stimulate Striga seed germination thereby allowing the parasite to infect and withdraw host nutrients. In Africa alone, the UN classifies Striga hermonthica infestations as the major cause of abject poverty on the continent. Understanding how Striga perceives SLs as a germination cue is therefore essential to developing agro-chemical strategies to combating this weed. We will establish a high throughput chemical genetics screening system to identify novel SL agonists and antagonists that bind SL receptors in Striga hermonthica. These chemicals will allow us to probe the complex SL receptor system in Striga without the need of sophisticated genetics or transgenic technologies. Furthermore, these probes can be used as leads in the development of Ag-biotech compounds to decrease Striga infestations.