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Antioxidants are not the only defence

Trehalose is an important stress protectant (Theve- lein, 1984; Van Laere, 1989; Wiemken, 1990), conferring stability to the plasma membrane and enzymes and additionally acting as a carbon source during starvation (Fales, 1951; Eaton, 1960; Chester, 1963; Panek, 1963). The level of trehalose is thought to be related to stress tolerance and adaptation (Thevelein, 1984; Van Laere, 1989; Hottiger et al., 1987a,b; DAmore et al., 1991; D'Hautcourt and Smart, 1999; Majara et al., 1996a,b; Conlin and Nelson, 2007). Trehalose is accumulated in response to heat shock (Hottiger et al., 1987a,b; Majara et al., 1996b; Iwashashi et al., 1995), exposure to toxic chemicals (Attfield, 1987), ethanol stress (Eleutherio et al., 1993; Mansure et al., 1994; Majara et al., 1996b), and osmotic stress (MacKenzie et al., 1988; Majara et al., 1996a).

Trehalose has also been implicated in the protection of yeast cells and cellular components against ROS (Benaroudj et al., 2001; Herdeiro et al., 2006). The genes involved in trehalose synthesis (TPS1, TPS2, TSL1, TPS3) and degradation (NTH1, NTH2, ATH1) (Francois and Parrou, 2001) are regulated by STRE elements and are up-regulated in response to various stresses, including oxidative stress (Parrou et al., 1997; Pedreno et al., 2002). Strains lacking the transcriptional activators Msn2p and Msn4p are unable to accumulate trehalose in response to stress (Parrou et al., 1997). Trehalose is known to inhibit the activity of essential enzymes, including glutathione reductase, which is involved in maintaining cellular homeostasis and reducing oxidative damage within the cell (Sebollela et al., 2004). It is thought that this inhibition saves the cell duplicating protective actions against ROS.

 
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