Arabidopsis dth9 mutation identifies a gene involved in regulating disease susceptibility without affecting salicylic acid-dependent responses.

To determine which components of the plant defense response make important contributions to limiting pathogen attack, an M(2) mutagenized population of a transgenic Arabidopsis line was screened for mutants showing constitutive expression of beta-glucuronidase activity driven by the promoter region of the CEVI-1 gene. The CEVI-1 gene originally was isolated from tomato plants and has been shown to be induced in susceptible varieties of tomato plants by virus infection in a salicylic acid-independent manner. We report here the characterization of a recessive mutant, detachment9 (dth9). This mutant is more susceptible to both virulent and avirulent forms of the oomycete Peronospora and also exhibits increased susceptibility to the moderately virulent bacterial pathogen Pseudomonas syringae pv maculicola ES4326. However, this mutant is not affected in salicylic acid metabolism and shows normal expression of pathogenesis-related (PR) genes after pathogen attack. Furthermore, after inoculation with avirulent pathogens, the dth9 mutant shows a compromised systemic acquired resistance response that cannot be complemented by exogenous application of salicylic acid, although this molecule is able to promote normal activation of PR genes. Therefore, the dth9 mutation defines a regulator of disease susceptibility that operates upstream or independently of salicylic acid. Pleiotropy is also evident in the dth9 mutant in the sense that the shoots of dth9 plants are insensitive to the exogenously applied auxin analog 2,4-dichlorophenoxyacetic acid.

Expression of a pathogen-induced gene can be mimicked by auxin insensitivity.

Following perception of a pathogenic attack, plants are able to develop a strong response with the corresponding activation of a plethora of defense-related genes. In this study we have characterized the mode of expression of the CEVI-1 gene from tomato plants, which encodes an anionic peroxidase. CEVI-1 expression is induced during the course of compatible viral and subviral infections, like many other defense-related genes, but is induced neither in incompatible interactions nor by signal molecules such as salicylic acid, ethylene, or methyl jasmonate. Additionally, CEVI-1 is induced in detached leaf tissues following a pathway distinct from that related to the classical wound response. We also describe the characterization of the structural CEVI-1 gene and compare the mode of expression in different transgenic plant species harboring a CEVI-1::GUS construct. Furthermore, we have isolated mutants in Arabidopsis, called dth mutants, that are deregulated in the control of expression of this gene. From the initial analysis of some of these mutants it seems that activation of CEVI-1 gene expression correlates with a defect in the perception of auxins by the plant. All these results may suggest that, during systemic infections with viruses, auxin homeostasis is one of the components participating in the regulation of the overall defense response.

Cirugía general mayor ambulatoria y de corta hospitalización: Experiencia de 5 años de trabajo

Se realizó un estudio prospectivo en el Servicio de Cirugía Mayor Ambulatoria y de Corta Hospitalización del Hospital Clinicoquirúrgico Docente "Miguel Enríquez", para conocer el número de intervenciones realizadas por este método, afecciones más frecuentes, tipos de anestesia y complicaciones; para ello se revisaron las historias clínicas de 3 254 pacientes intervenidos de enero de 1991 a diciembre de 1995; se agruparon por niveles, y se pudo observar que predominaron las hernias inguinales en el nivel II y la litiasis vesicular en el nivel III; se presentaron tan sólo 69 complicaciones.

A prospective study was conducted at the Service of Ambulatory Major Surgery and of Short Hospitalization of the "Miguel Enríquez" Clinical and Surgical Teaching Hospital to know the number of operations performed by this method, the most frequent affections, the types of anesthesis and complications. To this end, the medical histories of 3 254 patients who were operated on from January, 1991, to December, 1995, were reviewed, and grouped by levels. There was a predominance of inguinal hernias at level II and of vesicular lithiasis at level III. Only 69 complications were observed.

A tomato homeobox gene (HD-zip) is involved in limiting the spread of programmed cell death.

Antisense suppression in transgenic tomato plants of H52, a gene encoding a new homeodomain protein of the HD-Zip class, produces a conditional lethal phenotype. The transgenic lines that survive exhibit spontaneous misregulation of cell death control in leaves, which, once initiated, propagates and engulfs the entire leaf. Activation of defence genes, over-accumulation of ethylene and conjugated salicylic acid, and growth reduction of virulent pathogens also occurs in these plants. In wild-type plants, H52 is up-regulated upon infection, mirroring the generation of the oxidative burst which normally precedes the hypersensitive response (HR). Thus, H52 appears to be a transcription factor involved in cellular protection by limiting spread of programmed cell death in plants.

Cirugía general mayor ambulatoria y de corta hospitalización: Experiencia de 5 años de trabajo / Ambulatory major general surgery and of short hospitalization: a 5-year working experience

Se realizó un estudio prospectivo en el Servicio de Cirugía Mayor Ambulatoria y de Corta Hospitalización del Hospital Clinicoquirúrgico Docente "Miguel Enríquez", para conocer el número de intervenciones realizadas por este método, afecciones más frecuentes, tipos de anestesia y complicaciones; para ello se revisaron las historias clínicas de 3 254 pacientes intervenidos de enero de 1991 a diciembre de 1995; se agruparon por niveles, y se pudo observar que predominaron las hernias inguinales en el nivel II y la litiasis vesicular en el nivel III; se presentaron tan sólo 69 complicaciones (AU)

Characterization of LRP, a leucine-rich repeat (LRR) protein from tomato plants that is processed during pathogenesis.

This paper describes the isolation and characterization of LRP, a new gene from tomato plants. The deduced amino acid sequence showed that the encoded protein is enriched in leucine, and contains interesting structural motifs. LRP contains four tandem repeats of a canonical 24 amino acid leucine-rich repeat (LRR) sequence present in different proteins that mediates molecular recognition and/or interaction processes. Genomic organization and intron-exon arrangement of LRP favor the hypothesis that the LRR domains present in LRP evolved by exon duplication and shuffling. LRP expression analysis and immunohistochemical localization studies of the encoded protein indicate that the gene is under developmental regulation exhibiting tissue-specificity, particularly in certain cell types of the stele, like phloem fibers, parenchyma cells of the protoxylem, and in the cell files that constitute the rays of the secondary xylem. It is shown that this gene is upregulated in diseased tomato plants infected with citrus exocortis viroid. However, in this pathogenic context, LRP is processed proteolytically to a lower molecular weight form by a host-induced extracellular protease. The structural characteristics of LRP, its spatio-temporal pattern of expression, and its post-translational processing during pathogenesis, suggest this protein as a candidate molecule that may mediate recognition and interaction events taking place in the plant extracellular matrix under normal and/or pathogenesis-related conditions.