Biocontrol capacity of wild and mutant Trichoderma harzianum (Rifai) strains on Rhizoctonia solani 618: effect of temperature and soil type during storage

Wild (Th11, Th12 and Th650) and mutant (Th11A80.1, Th12A40.1, Th12C40.1 and Th650-NG7) Trichoderma harzianum strains were stored for 180 days at 5ºC or at 22ºC, in two types of soils. Strains recovered at 90, 120 and 180 days from the two types of soils, retained their full capacity to biocontrol Rhizoctonia solani 618, that produces crown and root rot of tomatoes. Recovery, estimated as colony forming units (cfu) of the wild and mutant strains, showed that all increased their cfu after storage independently of the type of soil and temperature, although kinetic behavior differed among strains. Ratios of recovery after storage in type B soil/ type A soil or at 22ºC/5ºC, higher or lower than one respectively, allowed to establish that Th11 and Th12 were the most appropriate strains for the biocontrol of R. solani in conditions where growth of the phytopathogen is optimal.

IP3 production in the hypersensitive response of lemon seedlings against Alternaria alternata involves active protein tyrosine kinases but not a G-protein

IP3 increase and de novo synthesis of scoparone are produced in the hypersensitive response (HR) of lemon seedlings against the fungus Alternaria alternata. To elucidate whether a G-protein and/or a protein tyrosine kinase (PTK) are involved in signal transduction leading to the production of such a defensive response, we studied the HR in this plant system after treatment with G-protein activators alone and PTK inhibitors in the presence of fungal conidia. No changes in the level of IP3 were detected in response to the treatment with the G-protein activators cholera toxin or mastoparan, although the HR was observed in response to these compounds as determined by the scoparone synthesis. On the contrary, the PTK inhibitors lavendustin A and 2,5-dihidroxy methyl cinnamate (DHMC) not only prevented the IP3 changes observed in response to the fungal inoculation of lemon seedlings but also blocked the development of the HR. These results suggest that the IP3 changes observed in response to A. alternata require a PTK activity and are the result of a G-protein independent Phospholipase C activity, even though the activation of a G-protein can also lead to the development of a HR. Therefore, it appears that more than one signaling pathway may be activated for the development of HR in lemon seedlings: one involving a G-protein and the other involving a PTK-dependent PLC.

The development of Alternaria alternata is prevented by chitinases and beta-1, 3-glucanases from Citrus limon seedlings

In addition to phytoalexin synthesis, the defense response of intact Citrus limon seedlings against Alternaria alternata involves both constitutive and induced enzyme activities such as chitinases (Ch) and beta-1,3-glucanases (Glu). A alternata conidial germination was prevented by protein extracts from inoculated lemon seedlings, but also by extracts from mock-inoculated specimens. On the other hand, degradation of mycelia was accomplished only by protein extracts from inoculated seedlings. The presence of six Ch isoenzymes and of four Glu isoenzymes was detected in protein extracts from mock-inoculated seedlings. As a result of fungal inoculation, the isoenzyme pattern of Ch and Glu changed, making possible the detection of a new Ch isoenzyme and of three new Glu. Also, some constitutive Ch and Glu increased their enzyme activity, and those Ch that increased their activity also showed a broadening of their substrate specificity. These changes were prevented by alpha-amanitin and cycloheximide, suggesting that the presence of new Ch and Glu isoenzymes was due to de novo synthesis of proteins. Results suggest that constitutive Ch and Glu could act as pre-formed defense molecules in Citrus limon preventing A. alternata germination, while those induced after fungal inoculation of lemon seedlings could act along with the former, to produce lysis of fungal mycelia, resulting in a more efficient control of A. alternata development.

Signal transduction in lemon seedlings in the hypersensitive response against Alternaria alternata: participation of calmodulin, G-protein and protein kinases

The development of an effective hypersensitive response (HR) in any plant system relies, not only in their gene composition and expression, but also on an effective and rapid signal transduction system. Lemon seedlings induce the phenylpropanoid pathway, which results in the de novo biosynthesis of the phytoalexin scoparone, as part of the hypersensitive response against Alternaria alternata. In order to elucidate some of the signaling elements that participate in the development of HR in lemon seedlings, we used several compounds that are known as activators or inhibitors of signal transduction elements in plants or in animal cells. Lemon seedlings treated either with cholera toxin or with phorbol 12-myristate 13-acetate (PMA), in the absence of A. alternata induced phenylalanine ammonia-lyase (PAL, E. C. 4.3.1.5) and the synthesis of scoparone, suggesting the participation of a G-protein and of a serine/threonine kinase, respectively, in signal transduction. The use of trifluoperazine (TFP), W-7, staurosporine, lavendustin A or 2,5dihydroximethyl cinnamate (DHMC) prevented PAL induction as well as scoparone biosynthesis in response to the fungal inoculation, thus allowing us to infer the participation of Calmodulin (CaM), of serine/threonine and of tyrosine protein kinases (TPK) for signal transduction in Citrus limon in response to A. alternata

Participation of the phosphoinositide metabolism in the hypersensitive response of Citrus limon against Alternaria alternata

Lemon seedlings inoculated with Alternaria alternata develop a hypersensitive response (HR) that includes the induction of Phenylalanine ammonia-lyase (PAL, E. C. 4.3.1.5) and the synthesis of scoparone. The signal transduction pathway involved in the development of this response is unknown. We used several inhibitors of the Phosphoinositide (PI) animal system to study a possible role of Inositol-1,4,5-triphosphate (IP3) in the transduction of the fungal conidia signal in Citrus limon. The HR was only partially inhibited by EGTA, suggesting that not only external but internal calcium as well are necessary for a complete development of the HR. In this plant system, Alternaria alternata induced an early accumulation of the second messenger IP3. When lemon seedlings were watered long term with LiCl, an inhibitor of the phosphoinositide cycle, the IP3 production was reduced, and the LiCl-watered plants could neither induce PAL nor synthesize scoparone in response to fungal conidia. Furthermore, neomycin, a Phospholipase C (PLC, E. C. 3.1.4.3) inhibitor, also inhibited PAL induction and scoparone synthesis in response to A. alternata. These results suggest that IP3 could be involved in the signal transduction pathway for the development of the HR of Citrus limon against A. alternata.

Un problema de difícil abordaje: el abuso sexual / A problem of difficult approach: sexual abuse

El maltrato infantil incluyendo el abuso sexual constituye un problema frecuente en la práctica médica. Considerando que el Pediatra no se halla preparado en diferentes aspectos para su encare y resolución, se realizó el siguiente trabajo que abarca: 1)revisión bibliográfica del tema a nivel nacional e internacional 2)un estudio retrospectivo de casos hospitalizados de Abuso Sexual Infantil (ASI) analizando sus principales características, así como el manejo médico de los mismos. Se observaron diferentes tipos y grados de abuso en la mayoría reiterados, un predominio de víctimas femeninas, abusadores predominantemente familiares y allegados. Respecto al manejo se destacan insuficiencias en la anamnesis, paraclínica e interconsultas efectuadas. 3) Se proponen pautas de diagnóstico y conductas a tomar ante un presunto caso de ASI como aporte al trabajo multidisciplinario que se viene desarrollando en nuestro medio