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RESEARCH PRODUCT

Polyamines in Developing Stress-Resistant Crops

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F.Marco,R.Alcazar,T.Altabella,P.Carrasco,SarvajeetSinghGill,NarendraTuteja,andA.F. TiburcioPolyamines (PAs) are small protonated compounds with key roles in plant devel-opmentandphysiologicalprocesses.PAsmayalsofunctionasstressmessengersinplant responses to different stress signals. Recent studies using exogenous appli-cation of polyamines and more contemporary genetic manipulation of polyaminelevelsincropsandmodelspeciespointtotheirinvolvementinstressprotection.Thedifferentmechanismsbywhichpolyaminesexerttheirfunctionsarepresentlybeingunraveledandinvolvedifferentmodesofactionthataresummarizedinthischapter.Polyamines are integrated with other stress-related hormone pathways, such asabscisic acid (ABA), reactive oxygen species (ROS) signaling, nitric oxide, andregulation of ion channels that are now being elucidated. Also, polyamines areimplicated in the transcriptional regulation to abiotic and biotic stresses as revealedin recent global transcriptome analyses. The genetic manipulation of polyaminelevels has been proven tobe anefficient tool for enhancing stress tolerance in manyplant species. A number of examples and their potential application to crops for asustainable agriculture are discussed in this chapter, along with the most recentadvances in our understanding of the regulation and mode of action of polyamines.27.1Introduction27.1.1PA Biosynthesis and Catabolism in PlantsPlants live in an ever-changing and often unpredictable environment that repre-sents the major limiting factors for agricultural crop productivity. Plants, unlikeanimals, cannot move and therefore encounter a variety of environmental stressesthroughout their life cycle. It is predicted that the environmental stresses willbecome more intense and frequent with climate change, especially global warming.Among abiotic stresses, cold, heat, salinity, and drought adversely affect plantgrowthandproductivityandrestrictthecropstoreachtheirfullgeneticpotential[1].Q1