Quantitative proteomics reveal factors regulating RNA biology as dynamics targets of stress-induced sumoylation in Arabidopsis.

The stress-induced attachment of small ubiquitin-like modifier (SUMO) to a diverse collection of nuclear proteins regulating chromatin architecture, transcription, and RNA biology has been implicated in protecting plants and animals against numerous environmental challenges. To better understand stress-induced SUMOylation, we combined stringent purification of SUMO conjugates with isobaric tag for relative and absolute quantification (iTRAQ) mass spectrometry and an advanced method to adjust for sample-to-sample variation to study quantitatively the SUMOylation dynamics of intact Arabidopsis seedlings subjected to stress. Inspection of 172 SUMO substrates during and after heat shock (37 degrees C) revealed that stress mostly increases the abundance of existing conjugates as opposed to modifying new targets. Some of the most robustly up-regulated targets participate in RNA processing and turnover, and RNA-directed DNA modification, thus implicating SUMO as a regulator of the transcriptome during stress. Many of these targets were also strongly SUMOylated during ethanol and oxidative stress, suggesting that their modification is crucial for general stress tolerance. Collectively, our quantitative data emphasize the importance of SUMO to RNA-related processes in protecting plants from adverse environments.

http://www.ncbi.nlm.nih.gov/pubmed/23197790?dopt=Abstract