Signal transduction during cold, salt, and drought stresses in plants.

Abiotic stresses, especially cold, salinity and drought, are the primary causes of crop loss worldwide. Plant adaptation to environmental stresses is dependent upon the activation of cascades of molecular networks involved in stress perception, signal transduction, and the expression of specific stress-related genes and metabolites. Plants have stress-specific adaptive responses as well as responses which protect the plants from more than one environmental stress. There are multiple stress perception and signaling pathways, some of which are specific, but others may cross-talk at various steps. In this review article, we first expound the general stress signal transduction pathways, and then highlight various aspects of biotic stresses signal transduction networks. On the genetic analysis, many cold induced pathways are activated to protect plants from deleterious effects of cold stress, but till date, most studied pathway is ICE-CBF-COR signaling pathway. The Salt-Overly-Sensitive (SOS) pathway, identified through isolation and study of the sos1, sos2, and sos3 mutants, is essential for maintaining favorable ion ratios in the cytoplasm and for tolerance of salt stress. Both ABA-dependent and -independent signaling pathways appear to be involved in osmotic stress tolerance. ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules and the ROS signaling networks can control growth, development, and stress response. Finally, we talk about the common regulatory system and cross-talk among biotic stresses, with particular emphasis on the MAPK cascades and the cross-talk between ABA signaling and biotic signaling.