Intersection of the Plant Epigenome and Bioenergetics in Phenotypy

S. Mackenzie, PI, University of Nebraska

M. Fromm, coPI, University of Nebraska

B. Yu, coPI, University of Nebraska

A. Lorenz, coPI, University of Nebraska

D. Wang, collaborator, University of Nebraska

J.-J. Riethoven, collaborator, University of Nebraska

Mitochondria and chloroplasts serve as bioenergetic focal points of the cell, compartmenting the metabolic underpinnings of cellular function. Likewise, they act as key environmental stress sensors, and are vital to processing plant defense responses. Yet, their integration to a systems model for the plant cell has been complicated by inability to perturb their functions with adequate specificity. This research team has implemented an elegant approach to alter mitochondrial and chloroplast properties that focuses on manipulation of a single nuclear gene, MSH1 (MutS homolog 1). Loss of MSH1 function produces organelle changes to condition distinct plant growth phenotypes without altering genotype of the plant. These include dramatic changes in growth rate, flowering time, reproduction, chloroplast development, and biotic and abiotic stress responses. it is postulated, as the central hypothesis to this research, that the msh1-associated organelle alterations cause heritable, programmed changes to the plant epigenome. The planned investigations capitalize on recent key observations involving MSH1, and implement cross-species comparative analysis in transcript profile-based dissection of emergent phenotypes. The project tests for msh1 effects on small RNA and DNA methylation changes, using Arabidopsis as an initial model for future tests in sorghum and soybean. The collaboration combines expertise in organelle biology, quantitative genetics, epigenetics and next-gen sequence technologies to investigate the influence of organelle signals on the plant epigenome. These studies address major unanswered questions in biology regarding the mode of trans-generational transmission of stress signals and the role of organelles as stress sensing components of the plant cell.

Broader impacts. Since Darwin's time, geneticists have speculated about the underlying basis of hybrid vigor and trans-generational adaptations to stress. While more recent evidence has suggested an epigenetic nature to these phenomena, direct investigation of the process linking bioenergetic or environmental sensing with epigenetic programs in the cell has generally been intractable. The system we investigate may prove invaluable in addressing these processes. Consequently, this research could have important implications for the plant breeding process and for our understanding of plant defense and adaptation. These studies will incorporate high school and undergraduate students in summer research activities, as part of our program to encourage careers in science research.