Jill M. Farrant

Physiological and metabolic processes associated with desiccation-tolerance

The changes in hydration levels and cellular stresses associated with water loss as proposed for seeds [10,11] are shown in Figure 2. While there has been no research on water properties in resurrection plants, our research has shown they experience similar stresses [reviewed in [12,13]] and the changes in water content and metabolic responses to desiccation are similar to those proposed for seeds (Figure 2. [11]). Initial water loss (type V water) is accompanied by osmotic adjustment to prevent turgor loss. With loss of type IV water (<0.7 gH2O gDW1) mechanical stress associated with decreasing cell volume [14,15] occurs and in seeds this is minimized by progressive cytoplasmic compaction resulting in membrane fusion, and protein and membrane denaturation is believed to be prevented by the replacement of water with solutes capable of substituting for the hydrogen bonds lost owing to dehydration [2123]. Additional stabilization of the subcellular milieu is believed to be achieved via cytosolic vitrification [10,23,24]. Solutes believed responsible for replacement and stabilization include: 1) sucrose and oligosaccharides [reviewed in [11,12]] and 2) proteins, particularly Late Embryogenesis Abundant (LEA) proteins (reviewed in [11,18,23,25]) and small heat shock proteins (sHSP) [2528]. Physiological and biochemical studies on resurrection plants have shown that all of these changes accompany desiccation in resurrection plants (Figure 2 [reviewed [12,13]]).

Extract from: Programming desiccation-tolerance: from plants to seeds to resurrection plants

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