Quantitative proteome and PTMome analysis ofArabidopsis thalianaroot responses to persistent osmotic and salinity stress

Abstract

Environmental conditions contributing to abiotic stress such as drought result in large annual economic losses around the world. As sessile organisms, plants cannot escape the environmental stresses they encounter, but instead must adapt to survive. Studies investigating plant responses to osmotic and/or salt stress have largely focused on short-term systemic responses, leaving our understanding of intermediate to longer-term adaptation (24 h - days), less well understood. In addition to protein abundance and phosphorylation changes, evidence suggests reversible protein acetylation may also be important for abiotic stress responses. Therefore, to characterize protein-level effects of osmotic and salt stress, we undertook a label-free proteomic analysis of Arabidopsis thaliana roots exposed to 300 mM Mannitol and 150 mM NaCl for 24 hours. We assessed protein phosphorylation, acetylation and changes in abundance, detecting significant changes in the status of 106, 66 and 447 proteins, respectively. Comparison with available transcriptome data from analogous treatments, indicate that transcriptome- and proteome-level changes occur in parallel. Furthermore, significant changes in abundance, phosphorylation and acetylation involve different proteins from the same networks, indicating a concerted, multifaceted regulatory approach to prolonged osmotic and/or salt stress. Lastly, our quantitative proteomic approach uncovered a new root elongation protein, Armadillo repeat protein 2 (ARO2), which exhibits a salt stress dependent phenotype. Collectively, our findings indicate dynamic protein-level changes continue to occur in plant roots 24 hours from the onset of osmotic and salt stress and that these changes differ across multiple levels of the proteome.