Coordination of vacuolar proton-pumps during cold acclimation
Final Report Abstract
Cold acclimation involves the accumulation of large amounts of solutes in the vacuole and it has long been assumed that the combined action of two vacuolar proton-pumps V-ATPase and V-PPase is required to maintain the proton-gradient that drives vacuolar uptake of cold-protective osmolytes. The cold-sensitivity that we identified in mutants lacking V-PPase activity seemed to confirm this notion, however our results show clearly that this phenotype is not caused by reduced tonoplast energization but by an overaccumulation of pyrophosphate (PPi). PPi is a by-product of over 200 metabolic reactions and in plants is tightly controlled by soluble inorganic pyrophosphatases (sPPase) as well as V-PPases, however their respective contributions in particular under stress conditions remain to be determined. The results of our phosphoproteome analysis show clearly that cold acclimation involves rapid and well-coordinated regulation of tonoplast proteins including V-ATPase and V-PPase. However, more work is required to demonstrate the physiological relevance of the detected phosphorylation events. Another important part of the cold acclimation involves changes in lipid composition to prevent freezing induced membrane injuries. Lipidomics data describing the changes in plasma membrane lipids upon cold treatment from different plant species are available. However, there are only a few studies investigating how the vacuolar membrane responds to low temperatures. Thus, we examined the changes in tonoplast lipid composition upon cold acclimation, and compared it to the plasma membrane. Taken together, the data obtained within this DFG-funded project provide important inroads to understanding the mechanisms of cold induced changes in the regulation of vacuolar proteins and their lipid environment.
Publications
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(2018) High V-PPase activity is beneficial under high salt loads, but detrimental without salinity. New Phyt 219, 1421-1432
Graus D, Konrad KR, Bemm F, Patir-Nebioglu MG, Lorey C, Duscha K, Güthofff T, Herrmann J, Ferjani A, Cuin TA, Roelfesema R, Schumacher K, Neuhaus HE, Marten I, Hedrich R
