Any microorganism that attempts to colonize a plant must contend with the cell wall. One of the most conspicuous effects of microorganisms on plant cell walls is enzymic degradation. Our interpretation of the significance of this depends on our concept of the plant cell wall, which, however, is paradoxical. On the one hand, the wall is an inert mechanical support and barrier; on the other hand, the wall is a dynamic, metabolically active organelle (Robinson, 1991, and refs. therein). The wall is a nutritional source for microorganisms and animals, yet it contains noxious peroxidases, phenolics, and activated oxygen (Cooper, 1984). The wall is mainly carbohydrate, yet its proteins are disproportionately studied (Showalter, 1993). Degradation poses another paradox. On the one hand, plant cell walls are the world's most abundant source of Glc and other sugars; on the other hand, parts of it are resistant to degradation. Since all the polymers of a plant cell wall are eventually degraded by microorganisms, for every type of chemical bond in the wall there must be an enzyme that can cleave it. Some polysaccharidases such as a-amylase are widespread in nature; others, such as ligninase, are very restricted in their distribution.

Deconstructing the Cell Wall.

The progress made in the molecular characterization of the mating types in several filamentous ascomycetes has allowed us to better understand their role in sexual development and has brought to light interesting biological problems. The mating types of Neurospora crassa, Podospora anserina, and Cochliobolus heterostrophus consist of unrelated and unique sequences containing one or several genes with multiple functions, related to sexuality or not, such as vegetative incompatibility in N. crassa. The presence of putative DNA binding domains in the proteins encoded by the mating-type (mat) genes suggests that they may be transcriptional factors. The mat genes play a role in cell-cell recognition at fertilization, probably by activating the genes responsible for the hormonal signal whose occurrence was previously demonstrated by physiological experiments. They also control recognition between nuclei at a later stage, when reproductive nuclei of each mating type which have divided in the common cytoplasm pair within the ascogenous hyphae. How self is distinguished from nonself at the nuclear level is not known. The finding that homothallic species, able to mate in the absence of a partner, contain both mating types in the same haploid genome has raised more issues than it has resolved. The instability of the mating type, in particular in Sclerotinia trifolorium and Botrytinia fuckeliana, is also unexplained. This diversity of mating systems, still more apparent if the yeasts and the basidiomycetes are taken into account, clearly shows that no single species can serve as a universal mating-type model.

Mating types and sexual development in filamentous ascomycetes.

Trust is an important aspect of mobile adhoc networks (MANETs). It enables entities to cope with uncertainty and uncontrollability caused by the free will of others. Trust computations and management are highly challenging issues in MANETs due to computational complexity constraints, and the independent movement of component nodes. This prevents the direct application of techniques suited for other networks. In MANETs, an untrustworthy node can wreak considerable damage and adversely affect the quality and reliability of data. Therefore, analyzing the trust level of a node has a positive influence on the confidence with which an entity conducts transactions with that node. In this work we present a detailed survey on various trust computing approaches that are geared towards MANETs. We highlight the summary and comparisons of these approaches. In addition, we analyze various works on trust dynamics including trust propagation, prediction and aggregation algorithms, the influence of network dynamics on trust dynamics and the impact of trust on security services.

Trust Computations and Trust Dynamics in Mobile Adhoc Networks: A Survey

Studies with model plants such as Arabidopsis thaliana have revealed that phytohormones are central regulators of plant defense. The intricate network of phytohormone signaling pathways enables plants to activate appropriate and effective defense responses against pathogens as well as to balance defense and growth. The timing of the evolution of most phytohormone signaling pathways seems to coincide with the colonization of land, a likely requirement for plant adaptations to the more variable terrestrial environments, which included the presence of pathogens. In this review, we explore the evolution of defense hormone signaling networks by combining the model plant-based knowledge about molecular components mediating phytohormone signaling and cross talk with available genome information of other plant species. We highlight conserved hubs in hormone cross talk and discuss evolutionary advantages of defense hormone cross talk. Finally, we examine possibilities of engineering hormone cross talk for improvement of plant fitness and crop production.

Evolution of Hormone Signaling Networks in Plant Defense

Traditional trust management schemes developed for wired and wireless ad hoc networks are not well suited for sensor networks due to their higher consumption of resources such as memory and power. In this work, we propose a new lightweight group-based trust management scheme (GTMS) for wireless sensor networks, which employs clustering. Our approach reduces the cost of trust evaluation. Also, theoretical as well as simulation results show that our scheme demands less memory, energy, and communication overheads as compared to the current state-of-the-art trust management schemes and it is more suitable for large-scale sensor networks. Furthermore, GTMS also enables us to detect and prevent malicious, selfish, and faulty nodes.

Group-Based Trust Management Scheme for Clustered Wireless Sensor Networks

Evidence for the requirement of extracellular protease in the pathogenic interaction of Pyrenopeziza brassicae with oilseed rape

The importance of risk in trust-based systems is well established. This paper presents a novel model of risk and decision-making based on economic theory. Use of the model is illustrated by way of a collaborative spam detection application.

Risk models for trust-based access Control(TBAC)

The inhibition of the hypersensitive response of potato tuber tissues by cytokinins: similarities between senescence and plant defence responses

Road congestion and traffic-related pollution have a large, negative social and economic impact, and we believe many of these problems can be reduced through investment in monitoring, distribution and processing of traffic information. This paper outlines how our on-going work on the TIME project (transport information monitoring environment) provides a solution, using traffic sensor systems and the design and development of an open and decentralised software framework. We also discuss how we address the privacy and security implications of the increased use of sensors and data processing.

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TIME: An Open Platform for Capturing, Processing and Delivering Transport-Related Data

Protoplasts were isolated from aseptic shoot cultures of commercial cultivars ofBrassica napus, B. oleracea andB. campestris, and from the six ‘rapid-cycling brassica species’. Of the rapid-cycling species, onlyB. napus responded well to the culture conditions used; 2% of protoplasts formed calli and up to 5% of calli regenerated shoots. Regeneration was also achieved from commercial cultivars ofB. napus andB. oleracea. For these two species the plating density, time of dilution with fresh medium and the composition of the shoot-inducing medium were all found to have an important influence on the efficiency of plant regeneration. Both responded better to maltose than to sucrose-based media. Under the optimum conditionsB. napus showed a plating efficiency of 7.8% and shooting efficiency of 17%; forB. oleracea the figures were 2% and 56%, respectively.

D.S. Ingram

Papers

Evidence for the requirement of extracellular protease in the pathogenic interaction of Pyrenopeziza brassicae with oilseed rape

Risk models for trust-based access Control(TBAC)

The inhibition of the hypersensitive response of potato tuber tissues by cytokinins: similarities between senescence and plant defence responses

TIME: An Open Platform for Capturing, Processing and Delivering Transport-Related Data

Studies of protoplast culture and plant regeneration from commercial and rapid-cycling Brassica species