The architecture of a plant, including stature and placement and arrangement of organs (leaves, branches, flowers), can influence yield potential, but also the physiological processes that help the plant adapt to its environment. In the Eveland lab, we study the developmental mechanisms that control plant architecture traits, and how the underlying regulatory networks interface with environmental challenges. Our research is focused around panicoid cereals, including economically important Zea mays (maize), stress resilient Sorghum bicolor (sorghum), and model system Setaria viridis. We use integrative genomics, developmental genetics, and high-resolution phenotyping to link genotype to phenotype and define genetic targets for improved architectures through breeding or genome editing.

A primary focus is inflorescence architecture, which is a key determinant of yield impacting seed number and harvesting ability in cereals. Cereal inflorescences display highly complex branching patterns, which are determined by the fate and determinacy of meristems, populations of self-renewing stem cells. Variation on inflorescence architecture is governed by the combinatorial action of transcriptional regulators and plant hormones. We study these factors including their spatiotemporal regulation, variation across genetic diversity, and how they respond to environmental challenges. We find that certain core regulatory modules controlling inflorescence architecture also work in various developmental contexts and contribute to other plant architecture traits such as leaf angle, tillering and plant height. A key question in the lab is how to decouple the pleiotropic effects of common developmental pathways.

This research addresses important agronomic challenges by identifying key genes and pathways as control points for yield, linking developmental and stress networks, and translating across grass species. Focus areas include:

Regulatory genomics to link genotype to phenotype – developmental networks and abiotic stress response.

A major emphasis in the Eveland lab is on the mechanisms of gene regulation. In particular, how suites of genes underlying developmental programs are regulated and how this varies in different spatiotemporal contexts, across genetic diversity, and in response to environment. To characterize important gene modules that control a certain trait, we make use of morphological transitions during plant development, the molecular phenotypes associated with them, and specific defects that arise from mutations in developmental modulators. Core determinants of gene regulation include cis-regulatory architecture and the combinatorial expression of transcription factors. We generate and integrate genomics datasets that capture these features in a given context, for example through co-expression networks, chromatin accessibility and transcription factor occupancy maps, to make predictions on regulatory factors that modulate specific phenotypes. Predictions are validated using genome editing and other experimental methods. Ultimately our goal is to predict the regulatory changes needed to alter phenotype (either architectural or stress resilience) in a desirable way, and how to engineer those changes with little disruption to the larger network within which they reside.  

Modulation of plant architecture by dynamic interplay of growth hormones, BR and GA.

Two plant growth hormones that underlie various architectural traits are brassinosteroids (BRs) and gibberellic acid (GA). In our mutagenesis screens for altered inflorescence phenotypes in the model C4 grass, Setaria viridis, we identified several mutants with meristem determinacy defects that were altered in BR or GA biosynthesis and signaling. While general pathways for these hormones have been extensively mapped out, little is known about the context-specificity of their action, for example in various aspects of cereal crop development. We are using S. viridis to explore the interactions between these hormones in meristem identity and determinacy during inflorescence development, which directly impacts seed set and grain yield. These discoveries are being translated to maize to study conserved and divergent features of this pathway in evolution and development. BRs and GA also play key roles in plant height and thus have been targets of selection in breeding programs for our most important cereal crops. We are also using S. viridis as a synthetic biology model for engineering inducible systems that target the GA pathway and using plant height as a measurable output response.  

The genetic and molecular basis for water and nitrogen use efficiency in sorghum.

Sorghum is a crop with innate resilience to various abiotic stresses such as drought and low nutrient inputs. On the outside, sorghum looks a lot like maize, which has been bred to thrive in optimal environments with lots of nitrogen fertilizer. Our interest in sorghum as a model for stress resilience is two-fold: i) To define genetic loci that contribute to its resilience for translation to maize and other related cereals, and ii) to improve sorghum for enhanced productivity on marginal lands as a high-yielding bioenergy feedstock. We use systems-level, multi-omics approaches to understand sorghum’s response to drought and low nitrogen stress at the molecular level, and how that varies across sorghum diversity. We also use high-resolution phenotyping in both controlled and field environments to link whole plant response to underlying molecular signatures. As part of a project funded by the US Department of Energy, we are using high-resolution, sensor-based phenotyping of sequence-indexed mutagenized populations of sorghum in controlled watering regimes, so we can link drought-responsive phenotype to gene function.