ROS-hormone interaction in regulating integrative défense signaling of plant cell

The elaborate redox network of the cell,comprising of events like turnover of reactive oxygen species(ROS),redox sensing,signaling,expression of redox-sensitive genes,etc.,often orchestrates with other bonafide hormonal signaling pathways through their synergistic or antagonistic action in the plant cell.The redox cue generated in plant cells under fluctuating environmental conditions can significantly influence other hormonal biosynthetic or signaling mechanisms,thereby modulating physiology towards stress acclimation and defense.There is also strong evidence of the recruitment of ROS as a‘second messenger’in different hormonal signaling pathways under stress.Moreover,the retrograde signaling initiated by ROS also found to strongly influence hormonal homeostasis and signaling.The present review,in this aspect,is an effort towards understanding the regulatory roles of ROS in integrating and orchestrating other hormonal signaling pathways or vice versa so as to unfold the relationship between these two signaling episodes of plant cells under environmental odds.We also accentuate the significance of understanding the utterly complex interactions,which occur both at metabolic and genetic levels between ROS and phytohormones during stress combinations.Furthermore,the significant and decisive role of ROS turnover,particularly the contribution of RBOH(respiratory burst oxidase homologs)in the synergism of redox and hormone signaling during systemic acquired acclimation under stress is also discussed.

Accumulation of Polyphenolic Compounds and Osmolytes under Dehydration Stress and Their Implication in Redox Regulation in Four Indigenous Aromatic Rice Cultivars

Present work was undertaken to screen some drought tolerant indigenous aromatic rice cultivars(IARCs),commonly cultivated in West Bengal,India,based on their capacity to produce osmolytes,redox-sensitive phenolic acids and flavonoids,as contrivances for redox-regulation under drought stress.Polyethylene glycol induced post imbibitional dehydration stress mediated changes in redox regulatory properties of the germinating seeds of the four IARCs(Jamainadu,Tulaipanji,Sitabhog,Badshabhog),which were assessed in terms of changes in prooxidant accumulation(in-situ localization of reactive oxygen species(ROS)by confocal microscopy,DCFDA(2′,7′-dichlorofluorescin diacetate)oxidation,O2-and H2O2 accumulation),cumulative antioxidative defense(radical scavenging property and total thiol content),ROS scavenging phenolic acids(gallic acid,protocatechuic acid,gentisic acid,para-hydroxy benzoic acid,chlorogenic acid,caffeic acid,syringic acid,salicylic acid,sinapic acid and p-coumaric acid)and flavonoids(catechin,naringin,rutin,quercetin,kaempferol,myricetin and apigenin).The capability of germinating seeds to accumulate osmolytes(like glycinebetaine,proline,soluble carbohydrates and K+ion)and polyphenolic compounds was also correlated with their corresponding redox status and redox biomarkers(conjugated diene,hydroperoxide,thiobarbituric acid reactive substances and free carbonyl content)produced under the same conditions.The results in general showed that accumulation of osmolytes along with the redox-sensitive phenolics and flavonoids conferred the ability to maintain the redox homeostasis under drought stress for the tolerant IARCs(Badshabhog and Tulaipanji).