CBF-Dependent Cold Stress Signaling Relevant Post Translational Modifications
Plants being sessile have developed intricate mechanisms to sustain and adapt to stress conditions. Cold/freezing stress leads to huge economical losses to crops, fruits and vegetables. Over last two decades a lot of research about transcriptional regulation of cold stress signaling has accumulated wealth of information but these studies have limitations as effect of post-transcriptional and post translational events cannot be analyzed. None the less, it is very well established that cold stress signaling could either be CBF dependent or independent. CBF dependent signaling regulates 12% cold responsive genes. The post translational regulation of CBF signaling is not very well understood. Therefore, an attempt has been made to summarize all cold stress relevant PTMs and their regulatory role in CBF dependent stress signaling. Currently more than 350 PTMs are known. Phosphorylation, redox based modifications of cysteine thiols (e.g. disulphide bonding and S-nitrosylation) and ubiquitinylation have been shown to be associated with cold signaling. Phosphorylation is one of the best known post-translational protein modifications. An important task of turning off the regulons is done by repressors and degradation through 26S proteasome via ubiquitination. ICE1, an upstream regulator of CBF dependent signaling is known to be post-translationally modified by ubiquitination and sumoylation. The RING finger protein HOS1, an E3 ligase physically interacts with ICE1 and mediates c(Zhao et al. 2009 in vivo and in vitro. Sumoylation prevents ubiquitination and thus might have role in protection of proteins. SIZ1, an Arabidopsis SUMO E3 ligase sumoylates ICE1, blocks its polyubiquitination resulting in its stabilization and increased activity. Role of S-nitrosylation as PTM in cold regulon is not clear yet but there are reports of it affecting DNA binding ability of AtMYB2. Significance of these PTMs in cold tolerance would be discussed.
KeywordsAttenuation Glutathione Serine Proline Lysine
c-repeat binding factor
Inducer of CBF expression
Post translational modifications
Partial financial support from DST/SAP/DST PURSE grants of government of India to RD and research fellowship to PK is acknowledged.
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