The engineering of stress response control determinants (Table 12.2) is more recent. Few transgenic experiments have been reported, specifically for salinity stress tolerance. From the analysis of tagged mutants in Arabidopsis, one might deduce a number of possibly fruitful avenues, in the categories of: TFs, mitogenactivated protein kinases (MAPKs), calcium-regulated signaling components (for example, the sos pathway genes), or site-directed mutants of these components that alter activity or activation of particular pathways.
However, one aspect that has to be considered in all engineering attempts is the effect of abiotic stresses on growth. Yeast and plants have been shown to include a signaling link that connects stress, the stress response, and growth retardation (Bressan et al., 2002; Hohmann, 2002; Zhu, 2001, 2002, 2003). As shown in Fig. 12.3, first outlined by Zhu (2001), abiotic stresses lead to typespecific responses (sos in the clearly documented case of salinity stress), but there are also general responses that extend beyond the specific elicitor. Most likely, these are responses to metabolic or hormonal deviations from a speciesspecific checkpoint or injury caused by the deviation in the form of, for example, ROS. It will require much work to address the dichotomy between protection and growth in the future.
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