RESEARCH-PGR: Genome-Wide Dissection of Leaf Angle Variation Across the Canopy in Maize

Plant architecture is the three-dimensional organization of the plant body. In addition to branching patterns, the size, shape, and position of leaves and flowering organs comprise the above-ground plant architecture. Leaf angle is the angle between the leaf and the plant stem.

In cultivated crops where a very large numbers of plants are packed into the field, leaf angle is a key determinant of the overall canopy leaf area, light capture, and yield of a given plant population. Technological advances have made it possible to obtain measurements from field-grown plants in a high-throughput fashion, to conduct tissue-specific gene expression analysis, and to precisely edit genes for functional characterization.

To capitalize these exciting advances, an interdisciplinary team was assembled to study leaf angle variation across the canopy in maize, an excellent model crop of economic and societal importance. The long-term goal is to enrich the fundamental understanding of the genetic control of leaf angle variation across the canopy in maize and to provide mechanistic insights into genetic manipulation of plant architecture for continued crop improvement.

Integration of research with education within the project will permit cross-training of the next generation of scientists with knowledge of developmental genetics, genomics, biotechnology, breeding, and agricultural engineering. As an excellent entry point to connect biology and agriculture with school gardens and children’s literature, leaf angle will be a key component of a K-12 teacher training certificate workshop that will be developed to help students learn about plant biology, domestication, agriculture, and crop improvement.

Leaf angle is a strategic component of plant architecture, and an important area of plant research that interconnects fundamental research on the mechanisms of plant development with plant breeding efforts for sustainable agricultural production. Long-term selection for greater agronomic yield by dense planting has generated superior maize hybrids with upright leaf angle.

However, a comprehensive understanding of the genetic mechanisms underlying leaf angle variation is still lacking. Due to the measurement difficulties, leaf angle is typically measured on a single leaf per plant in large-scale genetic studies. But leaf angle variation across the canopy is observed among different leaves of the same plant, and diverse inbreds are polymorphic for this “within-plant, leaf angle variation” phenotype.

In this project, genome-wide identification of genes underlying leaf angle variation across the canopy will be conducted using a high throughput phenotyping system (PhenoBot) to quantify multiple leaf angles at different nodes for genetic analyses. Transcriptomic analyses will be conducted through laser-microdissection RNA sequencing to examine genes and pathways underlying leaf angle variation across the canopy.

With a list of known genes from the literature and newly identified genes, functional validation and characterization of these genes will be carried out by generating edited maize plants with CRISPR-based tools. Grade-level text sets and accompanying seeds of diverse maize inbreds will be developed for the creation of teaching gardens on school grounds.

A certificate program in the form of a workshop will be developed to help K-12 teachers integrate the teaching garden into their curriculum.

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.