Divergent low water potential response in Arabidopsis thaliana accessions Landsberg erecta and Shahdara

The Arabidopsis thaliana accession Shahdara (Sha) differs from Landsberg erecta (Ler) and other accessions in its responses to drought and low water potential including lower levels of proline accumulation. However, Sha maintained greater seedling root elongation at low water potential and a higher NADP/NADPH ratio than Ler. Profiling of major amino acids and organic acids found that Sha had reduced levels of all glutamate family amino acids metabolically related to proline, but increased levels of aspartate-derived amino acids (particularly isoleucine), leucine and valine at low water potential. Although Sha is known for its different abiotic stress response, RNA sequencing and co-expression clustering found that Sha differed most from Ler in defence/immune response and reactive oxygen-related gene expression. HVA22B and Osmotin34 were two of the relatively few abiotic stress-associated genes differentially expressed between Ler and Sha. Insensitivity to exogenous glutamine and a different expression profile of glutamate receptors were further factors that may underlie the differing metabolism and low water potential phenotypes of Sha. These data define the unique environmental adaptation and differing metabolism of Sha including differences in defence gene expression, and will facilitate further analysis of Sha natural variation to understand metabolic regulation and abiotic/biotic stress interaction.