A Genome-Wide Association Study Assessing the Genetic Underpinnings for Response to Polyamine Cadaverine in Brachypodium distachyon

Abstract

Polyamines (PAs) are small organic molecules characterized as carbon chains with two or more amine groups, derived from the decarboxylation of amino acids. Plants possessing the requisite decarboxylase genes produce their own PAs and use them for a variety of purposes including the regulation of plant growth and development, tissue differentiation, and gene expression regulation. PAs are also stress metabolites in plants, accumulating in response to biotic and abiotic stimuli and contributing to stress mitigation. Microorganisms within the rhizo- phyllo- and endosphere take up amino acids, decarboxylate them into PAs, and often export them back out into the environment, where they can influence plant development. In plants, exogenous PAs have been demonstrated to modulate root system architecture, inhibiting primary root growth, promoting branching and altering growth behaviors, thereby favoring soil exploration to facilitate nutrients uptake. This study investigates the genetic basis of primary root growth responses to exogenous cadaverine in Brachypodium distachyon, under two light intensities, utilizing light intensity as an independent variable. Using a genome wide association study (GWAS) approach, we analyzed root growth data from a diverse panel of B. distachyon accessions exposed to the PA cadaverine under high and low light intensities. SNPs will identify gene regions associated with high or low light adaptations related to polyamine utilization pathways, and in doing so will aid in the characterization of cadaverine’s method of action. Root length measurements were normalized and subjected to GWAS using a mixed linear model to identify loci associated with cadaverine response. Significantly associated single nucleotide polymorphisms (SNPs) were mapped near and/or within genes potentially involved in cadaverine signaling and homeostasis under high, low and/or both light conditions. Our findings reveal that light modulates cadaverine’s impact on root growth and highlights candidate genes for future functional characterization.