ABSTRACT

Abbreviations ................................................................................................................................. 369 19.1 Introduction .......................................................................................................................... 370 19.2 PA Biosynthesis and Catabolism in Relation to Abiotic Stress Tolerance ........................... 371 19.3 Polyamines Involved in Abiotic Stress Signaling and Responses ........................................ 373

19.3.1 Salt Stress .................................................................................................................. 374 19.3.2 Osmotic Stress .......................................................................................................... 375 19.3.3 Water Stress .............................................................................................................. 376 19.3.4 Extreme Temperature Tolerance ............................................................................... 378 19.3.5 UV Stress .................................................................................................................. 379 19.3.6 Oxidative Stress ........................................................................................................380 19.3.7 Mineral Deciency and Heavy Metal Tolerance ......................................................380 19.3.8 Mechanical Stress ..................................................................................................... 381

19.4 Concluding Remarks ............................................................................................................ 381 References ...................................................................................................................................... 382

MAP Mitogen-activated protein MAPK Mitogen-activated protein kinase MAT Methionine adenosyltransferase m-RNAs Messenger ribonucleic acids NO Nitric oxide ODC Ornithine decarboxylase PA Polyamine PAO Polyamine oxidases PEG Polyethylene glycol Pro Proline PT Permeability transition Put Putrescine RMV1 Resistant to methyl viologen 1 ROS Reactive oxygen species SAM S-adenosylmethionine SAMDC S-adenosylmethionine decarboxylase SMO Spermine oxidase Spd Spermidine SPDS Spermidine synthase Spm Spermine SPMS Spermine synthase TMV Tobacco mosaic virus uORFs Upstream open reading frames

Abiotic stresses, especially salinity and drought, are the signicant causes of crop loss worldwide. Maintaining crop yields under adverse environmental stresses is probably the major challenge faced by modern agriculture where polyamines (PAs) can play an important role (Ahmad et al. 2012). Plant adaptation to environmental stress is dependent upon the activation of cascades of intricate molecular networks involved in stress perception, signal transduction, and the molecular expression of specic stress-related genes and metabolites (Vinocur and Altman 2005). Stress-induced gene expression leads to the synthesis of enzymes for the synthesis of compatible solutes such as amino acids, sugars, alcohols, and PAs (Quinet et al. 2010).