Characterization of Genetic Regulatory Networks Controlling Bifacial and Unifacial Leaf Morphology in Legumes

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This action funds an NSF National Plant Genome Initiative Postdoctoral Research Fellowship in Biology for FY 2018. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Dr. Aaron R. Leichty is "Characterization of Genetic Regulatory Networks Controlling Bifacial and Unifacial Leaf Morphology in Legumes". The host institution for the fellowship is the University of California-Davis and the sponsoring scientist is Dr. Neelima Sinha.The morphology of a leaf impacts plant physiology, which in turn determines where a plant can grow and reproduce. Plants adapted to arid environments often have leaves with morphological traits that are not found in plants that grow in wetter environments. This project examines the development of a striking adaptation to arid environments: the leaves of many woody legumes are vertically oriented and radially or vertically symmetric. Examining the similarities and differences in genetic regulatory networks underlying the leaves of major legume crops and the leaves of woody legumes may allow for the engineering of crops better adapted to a warmer, dryer, more variable climate. Training objectives include comparative developmental genomics, systems biology, bioinformatics, and gene expression and regulation in legumes. Broader impacts will include training opportunities for undergraduates and high school students and development of high school curriculum related to plant molecular biology, husbandry, and tissue culture. The goals of this project are to determine how bifacial and unifacial leaves develop in legumes. To determine how each leaf type is constructed, laser capture microdissection will be used to sample a series of developmental stages very early in leaf morphogenesis, when leaf identity and polarity are specified. These samples will be used for RNA-seq and the resulting data will be used to construct gene co-expression networks. Bioinformatic analyses will be used to identify important communities in the resulting networks. Communities from bifacial and unifacial networks will be compared to identify conserved components of each leaf type across species. Molecular and reverse genetic techniques will be used to validate the resulting networks. Specifically, transient and stable transformation will be used to perturb key genes in the identified genetic regulatory networks to confirm differences in regulatory connections within Acacia and Medicago. For the most promising genes, their unifacial expression pattern will be emulated in Medicago to see how easily bifacial development can be transformed into a unifacial-like morphology. The findings of this research will be shared publicly through presentation and publication. Sequence data and assemblies will be deposited to the NCBI Sequence Read Archive (http://www.ncbi.nlm.nih.gov/sra), the NCBI Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo/), the NCBI Genome resource (https://www.ncbi.nlm.nih.gov/genome) and linked through an applicable NCBI BioProject (https://www.ncbi.nlm.nih.gov/bioproject/).Keywords: comparative genomics, plant development, systems biology, gene networks, legumes, Medicago truncatula, AcaciaThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.