Inducing resistance: a summary of papers presented at the First International Symposium on Induced Resistance to Plant Diseases, Corfu, May 2000

The First International Symposium on Induced Resistance to Plant Diseases, organized by Eris Tjamos, brought together over 150 participants to discuss the complexities, questions and future direction of research on the mechanisms by which plants can become better able to defend themselves against pathogen attack. Although the term immunization has been used to denote treatments that enhance the defensive capacity of plants, the correspondence to vaccination in vertebrates is far-fetched: the induced state is by no means specific, but rather constitutes a more general increase in plant resistance to various types of pathogens. Moreover, it seldom prevents disease from occurring but generally reduces its extent or severity. These characteristics make induced resistance a powerful mechanism to exploit for enhancing the overall resistance in crop plants. Indeed, the first commercial chemical triggering induced resistance in plants, acibenzolar-Smethyl (BTH) was recently introduced on the market by Novartis under the tradenames Actigard (USA) and BION (Europe)

A Permeable Cuticle Is Associated with the Release of Reactive Oxygen Species and Induction of Innate Immunity

Wounded leaves of Arabidopsis thaliana show transient immunity to Botrytis cinerea, the causal agent of grey mould. Using a fluorescent probe, histological staining and a luminol assay, we now show that reactive oxygen species (ROS), including H2O2 and O2−, are produced within minutes after wounding. ROS are formed in the absence of the enzymes Atrboh D and F and can be prevented by diphenylene iodonium (DPI) or catalase. H2O2 was shown to protect plants upon exogenous application. ROS accumulation and resistance to B. cinerea were abolished when wounded leaves were incubated under dry conditions, an effect that was found to depend on abscisic acid (ABA). Accordingly, ABA biosynthesis mutants (aba2 and aba3) were still fully resistant under dry conditions even without wounding. Under dry conditions, wounded plants contained higher ABA levels and displayed enhanced expression of ABA-dependent and ABA-reporter genes. Mutants impaired in cutin synthesis such as bdg and lacs2.3 are already known to display a high level of resistance to B. cinerea and were found to produce ROS even when leaves were not wounded. An increased permeability of the cuticle and enhanced ROS production were detected in aba2 and aba3 mutants as described for bdg and lacs2.3. Moreover, leaf surfaces treated with cutinase produced ROS and became more protected to B. cinerea. Thus, increased permeability of the cuticle is strongly linked with ROS formation and resistance to B. cinerea. The amount of oxalic acid, an inhibitor of ROS secreted by B. cinerea could be reduced using plants over expressing a fungal oxalate decarboxylase of Trametes versicolor. Infection of such plants resulted in a faster ROS accumulation and resistance to B. cinerea than that observed in untransformed controls, demonstrating the importance of fungal suppression of ROS formation by oxalic acid. Thus, changes in the diffusive properties of the cuticle are linked with the induction ROS and attending innate defenses

A coleção fotográfica de Marcel Gautherot

Considering contemporary Anthropologys debate around photography, there is a\ud keen interest in the understanding of one of the most important open to public consultation\ud photographic collections on 20th Century Brazil, that of Frenchman Marcel Gautherot (1910-\ud 1996). The collection comprises around 25,000 photographs, purchased in 1999 by Instituto\ud Moreira Salles and kept in its fund in the city of Rio de Janeiro. The text comments on the\ud photographers work, linked to documentary projects under the patronage of institutions such as\ud the Musée de l´Homme in Paris, at the end of the 1930s, and both the National Historic and\ud Artistic Patrimony Service and the Brazilian Folklore Defence Campaign, in Brazil, between the\ud years of 1940 -1960. Such commitments and interests define important thematic groupings in\ud the production and organisation of his personal photographic archive. A discussion about criteria and technical procedures adopted by the photographer is attempted, detailing series\ud and visual narratives about Brazilian cultures density. With the photographs purchase by the\ud IMS, the oeuvres aesthetic quality, now as an institutional collection, is highlighted. The collections\ud manners of preservation and conservation, reproduction and circulation are redefined

The Protein Phosphatase 7 Regulates Phytochrome Signaling in Arabidopsis

The psi2 mutant of Arabidopsis displays amplification of the responses controlled by the red/far red light photoreceptors phytochrome A (phyA) and phytochrome B (phyB) but no apparent defect in blue light perception. We found that loss-of-function alleles of the protein phosphatase 7 (AtPP7) are responsible for the light hypersensitivity in psi2 demonstrating that AtPP7 controls the levels of phytochrome signaling. Plants expressing reduced levels of AtPP7 mRNA display reduced blue-light induced cryptochrome signaling but no noticeable deficiency in phytochrome signaling. Our genetic analysis suggests that phytochrome signaling is enhanced in the AtPP7 loss of function alleles, including in blue light, which masks the reduced cryptochrome signaling. AtPP7 has been found to interact both in yeast and in planta assays with nucleotide-diphosphate kinase 2 (NDPK2), a positive regulator of phytochrome signals. Analysis of ndpk2-psi2 double mutants suggests that NDPK2 plays a critical role in the AtPP7 regulation of the phytochrome pathway and identifies NDPK2 as an upstream element involved in the modulation of the salicylic acid (SA)-dependent defense pathway by light. Thus, cryptochrome- and phytochrome-specific light signals synchronously control their relative contribution to the regulation of plant development. Interestingly, PP7 and NDPK are also components of animal light signaling systems