The physiological and molecular mechanisms of tolerance to osmotic and ionic components of salinity stress are reviewed at the cellular, organ, and whole-plant level. Plant growth responds to salinity in two phases: a rapid, osmotic phase that inhibits growth of young leaves, and a slower, ionic phase that accelerates senescence of mature leaves. Plant adaptations to salinity are of three distinct types: osmotic stress tolerance, Na + or Cl − exclusion, and the tolerance of tissue to accumulated Na + or Cl − . Our understanding of the role of the HKT gene family in Na + exclusion from leaves is increasing, as is the understanding of the molecular bases for many other transport processes at the cellular level. However, we have a limited molecular understanding of the overall control of Na + accumulation and of osmotic stress tolerance at the whole-plant level. Molecular genetics and functional genomics provide a new opportunity to synthesize molecular and physiological knowledge to improve the salinity tolerance of plants relevant to food production and environmental sustainability.

https://rodas5.us.es/file/c2a700e9-8b4a-1970-d343-4a269c302970/1/estres_salino_bibliografia_scorm.zip/files/estres_salino_bibliografia.pdf

Mechanisms of salinity tolerance

Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Considering recent ROS-induced genome-wide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.

REACTIVE OXYGEN SPECIES: Metabolism, Oxidative Stress, and Signal Transduction

http://paymanhassibi.persiangig.com/document/mittler%20oxidative.pdf

Oxidative stress, antioxidants and stress tolerance

Intact spinach chloroplasts scavenge hydrogen peroxide with a peroxidase that uses a photoreductant as the electron donor, but the activity of ruptured chloroplasts is very low [Nakano and Asada (1980) Plant & Cell Physiol. 21: 1295]. Ruptured spinach chloroplasts recovered their ability to photoreduce hydrogen peroxide with the concomitant evolution of oxygen after the addition of glutathione and dehydroascorbate (DHA). In ruptured chloroplasts, DHA was photoreduced to ascorbate and oxygen was evolved in the process in the presence of glutathione. DHA reductase (EC 1.8.5.1) and a peroxidase whose electron donor is specific to L-ascorbate are localized in chloroplast stroma. These observations confirm that the electron donor for the scavenging of hydrogen peroxide in chloroplasts is L-ascorbate and that the L-ascorbate is regenerated from DHA by the system: photosystem I-*ferredoxin-*NADP^>glutathione. A preliminary characterization of the chloroplast peroxidase is given.

Hydrogen Peroxide is Scavenged by Ascorbate-specific Peroxidase in Spinach Chloroplasts

Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants

Roles for redox processes in adaptation to a high CO2 world

Significance The orchestration of shoot architecture, which is a major determinant of crop productivity, requires the regulated suppression or activation of -bud outgrowth. We show that light quality regulated tomato bud outgrowth is dependent on the mobile signaling protein HY5 and that HY5 dependent light signaling alone is sufficient to regulate bud outgrowth. HY5 promotes bud growth by direct and brassinosteroid mediated suppression of BRC1. BRC1 blocks the accumulation of cytokinin and gibberellin that regulate bud growth in tomato. In this way, HY5 represses gibberellin mediated stem elongation during photomorphogenesis while activating branching through BRC1 dependent phytohormone regulation. The HY5–BRC1 module thus plays predominant roles in the shoot architecture by orchestrating light quality dependent changes in stem elongation and bud outgrowth.

HY5 functions as a systemic signal by integrating BRC1-dependent hormone signaling in tomato bud outgrowth

Recently developed techniques that allow the estimation of the quantum efficiencies of photosystems I and II in vivo (1, 2, 3) have allowed us to adopt a quantitative approach to the analysis of the relationship between both photosystems and carbon assimilation (3, 4, 5). In this report we will describe the key findings of this and other related work which relates to the co-ordination of the quantum efficiencies of both photosystems, and the co-ordination of the thylakoids and the Calvin cycle activity.

The Relationship between the Efficiencies of Photosystems I and II and the Control of Electron Transport

© 2012 Landes Bioscience. Do not distribute. The ABA-INSENSITIVE-4 (ABI4) transcription factor links redox, hormone and sugar signaling pathways

Ribulose-1,5-bisphosphate (RuBP) carboxylase inlysed spinach (Spinacia okracea L.cvvirtuosa) chloroplasts that hadbeenpartly inactivated atlowCO2andMg2'byincubating indarkness with4millimolar partially purified RuBPwasreactivated bylight. Ifpurified RuBPwas usedtoinhibit darkactivation oftheenzyme, reactivation bylight was notobserved unless fructose-1,6-bisphosphate, ATP,orADPplus inorganic phosphate werealsoadded. Presumably, ADP plusinorganic phosphate acted asanATP-generating system witharequirement for thegeneration ofApHacross thethylakoid membrane. WhentheRuBP obtained fromSigma Chemical Co.wasused, light didnotreactivate the enzyme. Therewasnodirect correlation between ApHandactivation. Therefore, thylakoids arerequired intheribulose-1,5-bisphosphate carboxylase activase system largely tosynthesize ATP.Inactivation ofRuBP carboxylase inisolated chloroplasts orinthelysed chloroplast system wasnotpromoted simply byatransition fromlight todarkconditions butwascaused bylowCO2andMg2'.

Christine H. Foyer

Papers

Roles for redox processes in adaptation to a high CO2 world

HY5 functions as a systemic signal by integrating BRC1-dependent hormone signaling in tomato bud outgrowth

The Relationship between the Efficiencies of Photosystems I and II and the Control of Electron Transport

© 2012 Landes Bioscience. Do not distribute. The ABA-INSENSITIVE-4 (ABI4) transcription factor links redox, hormone and sugar signaling pathways

Regulation ofRibulose-1,5-Bis phosphate Carboxylase Activity bytheActivase System inLysedSpinach Chloroplasts