Table 2.

Problems caused by desiccation and mechanisms of desiccation tolerance

ProblemMechanismSelected references
Mechanical damage due to shrinkageIn plants, changes in cell wall composition that increase flexibility(Jones and McQueen-Mason, 2004; Vicre et al., 2004b)
In plants, folding cell walls(Vander Willigen et al., 2004)
In plants, replacement of water in vacuoles by non-aqueous compounds and fragmentation of vacuoles(Farrant, 2000; Vicre et al., 2004a)
Physiological damage at low intermediate water contentsUpregulation of proteins that increase membrane permeability(Smith-Espinoza et al., 2003; Vander Willigen et al., 2004)
Disintegration of membranes and aggregation of macromolecules during drying, coalescence of lipid bodies and membrane leakage upon rehydrationAccumulation of sugars, especially non-reducing disaccharides, that stabilize molecules, depress temperature (Tm) of membrane phase change from liquid crystal to gel, and form glasses with high melting temperature (Tg)(Wingler, 2002; Bernacchia and Furini, 2004; Buitink and Leprince, 2004; Crowe et al., 2005)
LEA proteins, which act as molecular chaperones and interact with sugars to form glasses(Wise and Tunnacliffe, 2004; Goyal et al., 2005a; Oliver et al., 2005)
Partitioning of amphiphiles into membranes(Hoekstra and Golovina, 2002; Oliver et al., 2002)
Small stress proteins, which may act as chaperones or repair damage upon rehydration(Collins and Clegg, 2004; Crowe et al., 2005; Potts et al., 2005)
Changes in lipid composition that stabilize membranes, such as increases in phospholipids, degree of saturation, and free sterols(Quartacci et al., 2002; Hoekstra, 2005)
In seeds, oleosins(Murphy, et al., 2001)
Generation of reactive oxygen species (ROS)Synthesis of antioxidants during drying, maintenance of pools of reduced antioxidants and ROS-scavenging enzymes(Shirkey et al., 2000; Augusti et al., 2001; Espindola et al., 2003; Kranner and Birtic, 2005)
In plants, downregulation of photosynthesis early in drying(Jensen et al., 1999; Deng et al., 2003; Hirai et al., 2004; Illing et al., 2005)
In plants, folding of leaves(Farrant et al., 2003)
Programmed chlorophyll loss(Tuba et al., 1996)
Triggering of cell death by oxidized glutathioneRapid reduction of glutathione upon rehydration(Kranner and Birtic, 2005)
In plants, disintegration of the photosynthetic apparatusModification of proteins in PSII(Peeva and Maslenkova, 2004)
Accumulation of damage from UV and gamma radiation and from Maillard and Fenton reactions while dryUV-absorbing pigments(Potts, 1996)
DNA repair(Wilson et al., 2004)
DNA protection(Potts et al., 2005)
In plants, cavitation of xylemHeight <3 m, low hydraulic conductivity(Sherwin et al., 1998)
Drying too fast for induction of tolerance mechanismsIn animals, contraction, construction of larval tube by Polypedilum(Kikawada et al., 2005)
In plants, signaling for induction of tolerance mechanisms via ABA(Beckett et al., 2000; Bartels and Salamini, 2001)