Rapid generation of superoxide and accumulation of H2O2 is a characteristic early feature of the hypersensitive response following perception of pathogen avirulence signals. Emerging data indicate that the oxidative burst reflects activation of a membrane-bound NADPH oxidase closely resembling that operating in activated neutrophils. The oxidants are not only direct protective agents, but H2O2 also functions as a substrate for oxidative cross-linking in the cell wall, as a threshold trigger for hypersensitive cell death, and as a diffusible signal for induction of cellular protectant genes in surrounding cells. Activation of the oxidative burst is a central component of a highly amplified and integrated signal system, also involving salicylic acid and perturbations of cytosolic Ca2+, which underlies the expression of disease-resistance mechanisms.

The oxidative burst in plant disease resistance

Programmed Cell Death in Animal Development

Calcium in Plants

Recognition of an avirulent pathogen triggers the rapid production of the reactive oxygen intermediates superoxide (O2-) and hydrogen peroxide (H2O2) This oxidative burst drives crosslinking of the cell wall, induces several plant genes involved in cellular protection and defence, and is necessary for the initiation of host cell death in the hypersensitive disease-resistance response However, this burst is not enough to support a strong disease-resistance response Here we show that nitric oxide, which acts as a signal in the immune, nervous and vascular systems, potentiates the induction of hypersensitive cell death in soybean cells by reactive oxygen intermediates and functions independently of such intermediates to induce genes for the synthesis of protective natural products Moreover, inhibitors of nitric oxide synthesis compromise the hypersensitive disease-resistance response of Arabidopsis leaves to Pseudomonas syringae, promoting disease and bacterial growth We conclude that nitric oxide plays a key role in disease resistance in plants

Nitric oxide functions as a signal in plant disease resistance

The production of reactive oxygen species (ROS), via consumption of oxygen in a so-called oxidative burst, is one of the earliest cellular responses following successful pathogen recognition. Apoplastic generation of superoxide (O2−), or its dismutation product hydrogen peroxide (H2O2), has been

Reactive Oxygen Species Signaling in Response to Pathogens

Calcium-mediated apoptosis in a plant hypersensitive disease resistance response

The English common law of real property, as S.F.C. Milsom has argued, took shape between 1153 and 1215. The common law gave royal protection to free tenements, replacing feudal relationships as the primary bond structuring society. The law thus constituted the institutional core of the English state. But no Machiavellian monarch constructed the English state. Henry II was, rather, a king who presumed the morality and necessity of feudal relationships. His innovations, though intentional and carefully planned, were directed at narrower and less far-sighted ends. Other changes were the result of bureaucratic action. The complex interplay between present-oriented political or juridical decisions and bureaucratic rigor generated a legal system.

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The Origins of Property in England

Robert Palmer's pathbreaking study shows how the Black Death triggered massive changes in both governance and law in fourteenth-century England, establishing the mechanisms by which the law adapted to social needs for centuries thereafter. The Black Death killed one-third of the English population between 1348 and 1351. To preserve traditional society, the king's government aggressively implemented new punitive legal remedies as a mechanism for social control. This attempt to shore up traditional society in fact transformed it. English governance now legitimately extended to routine regulation of all workers, from shepherds to innkeepers, smiths, and doctors. The new cohesiveness of the ecclesiastical and lay upper orders, the increase in subject matter jurisdictions, the growth of the chancellor's court, and the acceptance of coercive contractual remedies made the Black Death in England a transformative experience for law and for governance. Palmer's book, based on all of the available legal records, establishes a genuinely new interpretation and chronology of these important legal changes.

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English Law in the Age of the Black Death, 1348-1381: A Transformation of Governance and Law

The development of property in England between 1176 and 1220 was the result of a complicated interaction between social mores made law and bureaucratic action. In the Assize of Northampton, Henry II undertook regular supervision of proprietary decisions to prevent his men from preparing a rebellion like that of 1173-74. The supervision assumed peacetime feudal norms, but in the hands of bureaucratic justices even prior to 1200 this supervision increasingly restricted lords' power to discipline their tenants, at a time when disciplinary power was far more important than proprietary decisions. By 1220, the relative importance of proprietary matters and disciplinary power had been reversed. But proprietary action by the lord was so attenuated that seisin—lawful possession—was possible now even without lordly acceptance. Such insulation of the tenant from his lord was a bond established between the tenant and his tenement: property.

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The Economic and Cultural Impact of the Origins of Property: 1180-1220

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Robert C. Palmer

Papers

Calcium-mediated apoptosis in a plant hypersensitive disease resistance response

The Origins of Property in England

English Law in the Age of the Black Death, 1348-1381: A Transformation of Governance and Law

The Economic and Cultural Impact of the Origins of Property: 1180-1220

The Feudal Framework of English Law