"Review of literatureturgor pressure might be a major trigger at the molecular level. Some receptors likeNtC7 was identified in plants in response to wounding, salt, and osmotic stress, andsuggested as a probable candidate for sensing osmotic stress. The overexpression of NtC7 gene encodes a receptor-like membrane protein intransgenic tobacco plant has improved osmotic stress tolerance induced by mannitol,however, no such result was seen in the osmotic stress induced by NaCl (Tamura et al.,2003). Involvement of PRR receptor in signal perception in herbivore attack by Princeet al., (2014) CRE1 (Cytokinin Response 1) is a cytokinin receptor from Arabidopsis acandidate for sensing osmotic stress in plants (Reiser et al., 2003). SLN1 is anothercandidate involve in signal perception, having similar organizations of the cytoplasmichistidine kinase and receiver domains as CRE1 (Boudsocq and Lauriere, 2005). Signal TransductionDiscovering environmental stress perception and transduction networks is ofemerging scientific interest since it is of critically important for the development ofstress tolerant crop. Progress has been made in recent years towards understandingthe receptor molecules and their interaction with other signalling molecules like,2+ kinases and phosphatases, phospholipids, ROS, Ca , nitric oxide, cAMP and sugars,which play an important role in signal transduction (Golldack et al., 2014; Bakshi andOelmüller, 2014), which in turn activate stress associated TFs. Many researchers havefocused on the signaling mechanisms that are activated by water stress ( Laloum et al.,2013). These signaling pathways comprise a network of protein-protein interactionsand signaling molecules.ABA-mediated signallingPlant hormones regulate diverse process in plants, which enable acclimation tostress. In spite of being a growth regulator, ABA also acts as a messenger in the22 Review of literatureresponse of the plant to biotic and abiotic stress (Zhang et al., 2015). Increased levels ofABA during plant cellular adaptation to drought and salinity was previously reported(Golldack et al., 2014; Weiner et al., 2010). A similar result was reported by Zeller etal., ( 2009) in a transcriptome analysis of Arabidopsis plant under stress conditions.ABA also serves as a mechanism for pathogen defense (Joshi-Saha et al., 2011). ABAbinding is mediated by a combination of hydrogen bonds and hydrophobicinteractions. Several groups of protein that act as soluble ABA receptors have beenidentified so for in different plants (Gonzalez- Guzman et al., 2014; Tian et al., 2015).Once ABA enters into the receptor pocket, SGLPA ‘gate’ loop and the HRL ‘latch’loop, flank the ligand- binding pocket and undergo a conformational rearrangementto seal in ABA. In the absence of ABA, the ABA- PP2Cs ABI1, ABI2, and HAB1interact with SnRK2 kinases and dephosphorylate a critical phosphoserine residue thatis required for SnRK2 kinase activity (Melcher et al., 2010). Joshi et al., (2016) hasproposed diagrammatic model representing the activation of ABA under drought stressand its signaling pathway for activation of downstream TF elements like NAC, MYB,MBK, and bZIP (Figure 3).MAP kinasesProtein kinases regulate the expression of other genes involving in stresstolerance (Todaka et al., 2015). Protein kinases like Mitogen-activated protein kinase(MAPKs) play a major role in controlling cellular functions in response to externalsignals. MAPKs are involved in directing cellular responses to external stimuli, suchas osmotic stress, drought stress, and heat shock. MAPK cascade includes three proteinkinases like MAPK, MAPKK, and MAPKKK (Hamel et al. 2006). These protein kinasesform a signaling cascade located on the plasma membrane and translocate MAPK to thenucleus to regulate gene expression. Translocation of the MAPK into the nucleus brings23 Review of literatureabout the activation of TFs through phosphorylation. MAPKs are catalytically inactivein their base form; to activate they must be phosphorylated at their conserved threonineand tyrosine residues. MAPK pathways include a variety of upstream signals throughthe interaction of other kinases , G proteins and TFs (Chi et al., 2013). The involvementof MAP kinase cascades in biotic and abiotic stresses response and the defense wasreported in various studies (Sinha et al., 2011; Liu 2012). MAPKs driven activation ofWRKY transcription factor by two and its involvement in pathogen-responsive wasreported in Arabidopsis (Mao et al., (2011) and drought stress response in rice wasreported in earlier studies (Shen et al., 2012).SNF1-like kinasesSNFl/AMP (SNF: sucrose-non-fermenting) activated protein kinases were firstanalyzed from the yeast. SNF1 serine/threonine protein kinase family members playessential roles in eukaryotic glucose metabolism and stress signaling. These kinasesmay sense the ATP/AMP ratio and thus controls the carbohydrate metabolism throughtranscription of genes encoding the enzymes related to the metabolism. In yeast cells,SNF kinases are known to involve in respiration, sporulation, carbon source utilization,gluconeogenesis, thermotolerance, and cell cycle. SNF1 homologs SnRK1 have beencloned from a range of plants ( Man et al., 1997; Du et al., 2011). SNF1- related proteinkinases (SnRKs) have been classified into three families, SnRK1, SnRK2, and SnRK3with unknown function (Halford and Hardie, 1998). The SnRK2 are known to involvein ABA-dependent signaling pathway was reported previously by vilela et al., (2015).In plants, some members of this group of kinases are expressed in response tonitrate reductase, sucrose synthase, and sucrose phosphate synthase (SPS) productionand in response to dehydration. Ten protein kinases belonging to SNFl class, activatedby osmotic stress and by ABA were identified by Kobayashi et al., (2004) in the rice24 "