Plant Nutrient-Growth Signaling Network

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Nutrient signaling integrates and coordinates gene expression, metabolism, and growth. In multicellular organisms, growth factors and hormones are ineffective in growth promotion without the support of nutrient signaling networks. However, surprisingly little is known about the primary nutrient signaling mechanisms in plants and animals. Plants play a central role in bridging the conversion of inorganic nitrogen to organic nitrogen in the global nitrogen cycle by assimilating inorganic nitrate to generate amino acids, nucleic acids, and organic nitrogen-carbon molecules, which are essential to build and sustain lives from plants to humans. Despite the fundamental and multifaceted regulatory roles of nitrate in gene expression, metabolism, growth, and development, the molecular and cellular mechanisms of nitrate signaling remain largely elusive in multicellular plants. Hampered by gene redundancy and mutant lethality, classical genetic screens had limited success in identifying key nitrate signaling components in plants over the past two decades. By taking integrated molecular, cellular, biochemical, functional genomic, chemical genetic, and systems analyses, we have discovered a surprising molecular link between specific Ca2+-sensor protein kinases (CPKs) and the NODULE INCEPTION-LIKE PROTEIN (NLP) transcription factors as the primary regulators of the nitrate-signaling network in plants. Our research has demonstrated the unique role of nitrate as a central signaling molecule in transcriptome reprogramming and shoot-root coordination to shape organ biomass and architecture. We also recently discovered the first plant nitrate sensor NLP7 with a dual function as a transcription activator, and the combinatorial actions of multiple NLPs in controlling the primary nitrate responses (PNR) central to coordinate plant root and shoot development. We propose to build on our new findings and innovative experimental platforms to elucidate the molecular and cellular basis of the nutrient-growth network that orchestrates system-wide transcription and modulates plant developmental processes. We will integrate complementary strategies and methodologies to advance our understanding of nutrient signaling mechanisms for three specific aims: Aim1. Elucidate the function and action of the NLP7 nitrate sensor complex Aim 2. Dissect the intracellular Ca2+ signaling mechanism triggered by nitrate Aim 3. Uncover the CPK-TOR link in nitrate signaling The proposed research to unravel the nitrate signaling mechanisms will establish new paradigms in the action of nutrient sensor complexes, nutrient-mediated Ca2+ signaling, as well as transcriptional and developmental regulation with sustained scientific impact beyond plant biology.