ECA-PGR: Under the Hood: The Genetic Components of Maize Transformation

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Maize (corn) is a staple crop in the US and worldwide, and serves as an important model for fundamental research. Maize production has experienced dramatic yield increases over the last century but faces challenges for further increases, particularly under highly variable climates and disease pressures. Revolutionary genome engineering tools (genome editing) offer great opportunities for improved understanding of the relationship between genetic information and traits, and for modifying genetic features for trait improvements. Unfortunately, most crop plants, including maize, are not readily amenable to plant tissue culture, thereby limiting the benefit from direct applications of genome editing tools. In this project, the genome of a maize line amenable to culture will be sequenced to facilitate the identification of the genetic elements that regulate culturability. Novel approaches will be developed for genetic decoding on the complex maize genome. In particular, a designable bacterial system specifically interacting with genes of interest in the maize genome will be utilized to study gene function and manipulate cell development. The project will also provide training for undergraduate, graduate and postdoctoral students in both genetics and computation, with an emphasis on large data education. In addition, the project will collaborate with the Kansas Louis Stokes Alliance for Minority Participation to encourage involvement of historically underrepresented students in STEM fields.Maize is the highest agronomically valued crop in the US. Genome engineering tools, including TALENs and CRISPRs, provide great potential for the elucidation of maize gene functions and trait improvements. However, current genetic and genomic resources as well as transformation capacity in maize are insufficient for the full utilization of genome engineering tools. This project provides public resources that include a high-quality genome assembly of a highly transformation amenable maize inbred line, A188, and 150 doubled haploid (DH) lines from a cross of A188 with B73, a transformation recalcitrant inbred variety and the maize reference genome. Bulked RNA sequencing based mapping will be used for genetic mapping of traits related to embryogenesis and regeneration. Furthermore, the project will generate time-series transcriptome profiles from callus cells that are transiently expressing designer Transcription Activator-Like effectors (dTALes) of a known regulator of embryogenesis and regeneration. These profiles will be used to construct multilayered hierarchical gene regulatory networks to identify high hierarchical regulators and hub genes that govern maize embryogenesis and regeneration. Ectopic gene expression and CRISPR-Cas9 gene editing will be used to validate select candidate genes. These genetic and genomic resources will advance genome engineering in a major crop species and improve understanding of the genetic basis of maize transformation and regeneration ability.This 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.