Department of Plant Sciences

It is of fundamental importance to understand the physiological differences leading to salt resistance and to get access to the molecular mechanisms underlying this physiological response. Initial responses of plant cells after immediate stress application are of special interest for elucidating the physiological processes and signals of salt resistance. Especially post-translational modification such as protein phosphorylation is an important part of the stress related signal at the initial phase. The aim of the present work was to investigate the protein phosphorylation after a short-term salt exposure of maize and to elucidate the role of proteins which may contribute to leaf expansion. We therefore focus to the initial effects after the adjustment to saline conditions in the first hour after sodium ions entered the cell. The subsequent protein phosphorylation was monitored using a two dimensional proteomics approach. A set of phospho-proteins in maize was detected but only 12 proteins were phosphorylated and 8 proteins which were dephosphorylated after the application of 25 mM NaCl for 1 h. Some of the phosphorylated maize proteins such as glucosyl transferase BX9, a 2-Cys-peroxyredoxine, a xyloglucane-endotransglycosylase were enhanced after initial salt stress whereas an isocitrate-dehydrogenase, a maturase, calmodulin and a 40-S-ribosomal protein were dephosphorylated after adjustment to saline conditions. In conclusion, the phospho-proteome of maize showed a distinct, fast and initial reaction under moderate saline conditions which contributes to the adaptations to salt stress of maize.