ABSTRACT
Stress Tolerance ................................................................................... 335 13.3 Development and Application of Molecular Markers ......................... 337 13.4 Molecular Breeding and Marker Assisted Selection ........................... 341 13.5 Stress Responsive Genes and Their Regulation .................................. 343 13.6 LEA-Protein ........................................................................................ 346 13.7 Regulatory Genes ............................................................................... 346 13.8 Functional Genomics and Stress Response ......................................... 347 13.9 Modern Transgenic Approaches for Abiotic Stress Tolerance ............ 349 13.10 Metabolic Engineering for Stress Tolerance ....................................... 351 13.11 Conclusion and Future Perspectives ................................................... 356 Keywords ....................................................................................................... 357 References ...................................................................................................... 357
13.1 INTRODUCTION
Abiotic stresses such as high temperature, low temperature, drought, flooding, salinity, heavy metals, radiation, ozone are the most threatening and limiting factors for agricultural productivity worldwide (Doupis et al., 2011; Hasanuzzaman et al., 2009; Hasanuzzaman et al., 2010; Hasanuzzaman et al., 2011; Hasanuzzaman et al., 2012; Hasanuzzaman et al., 2013a; Hasanuzzaman et al., 2013b; Hasanuzzaman and Fujita, 2012). These stresses negatively influence the survival of crop plants, leading to losses of up to 70 % in biomass production and yields of staple food crops (Kaur et al., 2008; Thakur et al., 2010) and decreases of as much as 50 % in overall productivity (Rodríguez et al., 2005; Acquaah, 2007). For these reasons, abiotic stresses threaten food security worldwide. The degree of severity of stress and the plasticity of the plants determine the types of morphological, anatomical, and physiological changes that adversely affect plant growth, metabolic profile, nutritional potential, developmental processes, and productivity (Altman, 2003). At the molecular level, abiotic stresses lead to an enhanced production of reactive oxygen species, which cause peroxidation of lipids, oxidation of proteins, damage to nucleic acids, enzyme inhibition, and-at extreme conditions-programmed cell death and even the death of the entire plant (Mittler, 2002; Sharma and Dubey, 2005; Sharma and Dubey, 2007).
