Role of Tomato bHLH Transcription Factors in Development and Immunity

Stanford University, Stanford CA

Investigators

Abstract

Plant growth is influenced by multiple extracellular signals including hormones, circadian clock, developmental and environmental cues, and pathogen elicitors. These signals act through distinct and overlapping signaling pathways, which have been studied extensively. The key factors that control and integrate interactions between these pathways however remain poorly understood at the gene regulation level. A plant's ability to prioritize tradeoffs between growth and defense is critical for optimizing its fitness in an ever-changing environment. How growth- defense tradeoffs are regulated at the molecular level is largely unknown and is a central question in plant biology. Recent evidence suggests that transcription factors (TFs) of the basic helix-loop-helix (bHLH) class play important roles in regulating gene expression networks that control growth-defense trade-offs. The goal of this project is to study unknown bHLH TFs in tomato, a representative crop of the Solanaceae and the third most valuable crop family in the world, to provide new knowledge regarding: (1) the transcription circuits that play a major role in tomato growth and defense; (2) the factors that regulate these transcription circuits; and (3) the potential pathways that can be engineered to enhance disease resistance while optimizing plant fitness. Ongoing international collaboration will provide a framework to share emerging concepts, tools and technology. This research will provide hands-on research and mentorship training at the graduate, undergraduate, and high school level with special consideration of women, underrepresented minorities, low-income students, and disabled students. Outreach partnerships with high schools will provide curriculum development, laboratory upgrades, technical support and enrichment training for teachers and students. Sparse information is available about the transcription factors (TFs) and transcription networks in crop plants that integrate multiple signals to optimize fitness in response to pathogen attack and how they are manipulated by pathogens. Recent evidence suggests that the tomato pathogen Xanthomonas euvesicatoria specifically regulates basic helix-loop-helix (bHLH)- controlled transcription circuits to dynamically alter tomato growth and immunity to promote pathogenesis. One of these networks in roots is required for lateral root development and is hypothesized to impact the efficiency of nutrient acquisition. The goals of this research is to: (1) use RNAseq and ChipSeq technologies to study the DH1 transcription network(s) controlling development and immunity in tomato; (2) determine how Xanthomonas directly alters the transcription complex that controls DH1 transcription in tomato leaves to provide mechanistic insight for how pathogens manipulate TF-modules during infection; and (3) define additional bHLH TFs that function in growth and/or immunity in tomato. This information will be used to engineer novel approaches to optimize growth in important crops. Ongoing international collaboration will provide a framework to share emerging concepts, tools and technology. This research will provide hands-on research and mentorship training at the graduate, undergraduate, and high school level with special consideration of women, underrepresented minorities, low- income students, and disabled students. Outreach partnerships with high schools will provide curriculum development, laboratory upgrades, technical support and enrichment training for teachers and students.