ABSTRACT
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.
Subject(s)
Alternaria/pathogenicity , Citrus/physiology , Citrus/virology , Phosphatidylinositols/metabolism , Signal Transduction , Caffeine/pharmacology , Calcium/pharmacology , Coumarins/antagonists & inhibitors , Coumarins/metabolism , Fibrinolytic Agents/pharmacology , Heparin/pharmacology , Inositol 1,4,5-Trisphosphate/physiology , Neomycin/pharmacology , Phenylalanine Ammonia-Lyase/metabolism , Phosphatidylinositols/antagonists & inhibitors , Phosphodiesterase Inhibitors/pharmacology , Protein Synthesis Inhibitors/pharmacology , SeedsABSTRACT
La hipertermia maligna es un síndrome farmocogenético asociado con la alteración de la regulación del calcio mioplásmico. Una modificación en el metabolismo del inositol 1,4,5 trifosfato (InsP3), hasido asociada con la fisiopatología de la hipertermia maligna. El objetivo del trabajo fue estudiar el efecto del InsP3 sobre la concentración intracelular de calcio ([CA²+]i) en fibras musculares obtenidas de sujetos no susceptibles y susceptibles a hipertermia maligna. La [CA²]i fue cuantificada mediante el uso de microelectrodos sensibles a CA²+. En susceptibles a hipertermia maligna la [CA²+]i fue más elevada que en las fibras musculares no suceptibles hipertemia maligna. La microinyección de InsP3 0,5 y 1 µM indujo una elevación significativa de la [CA²+]i, en ambos grupos musculares. Sin embargo, este incremento fue mayor en las fibras susceptibles a hipertermia maligna que en las no susceptibles a hipertermia maligna. La incubación de los músculos en soluciones con bajo contenido en Ca²+ o en nifedipina (10 µM) no modificó la elevación de [Ca²+]i mediana por el InsP3. El tratamiento con dantrolene (50 µM) redujo la [Ca²+]i, y bloqueó la elevación de la [Ca²+]i, inducida por el InsP3 en ambos grupos. Estos resultados sugieren (i) el posible papel del InsP3 como mediador químico en la liberación de Ca²+ desde los depósitos intracelulares; (ii) que el InsP3 podrá jugar un papel importante en la fisiopatología de la hipertermia maligna y (iii) que el efecto profiláctico y terapeútico del dantrolene podría estar relacionado con su efecto inhibitorio sobre la liberación de calcio intracelular mediada por el InsP3
Subject(s)
Humans , Female , Male , Inositol 1,4,5-Trisphosphate/physiology , Calcium , Malignant Hyperthermia/diagnosis , Malignant Hyperthermia/metabolism , Malignant Hyperthermia/pathologyABSTRACT
Invertebrate visual transduction involves a second messenger cascade process that leads to an increase in membrane conductance. The identity of the second messenger that gates the light-dependent channels is presently a major focus of attention. Cyclic GMP, inositol trisphosphate and Ca2+ are the most likely candidates for being such a messenger in the species studied so far. Here we review the available evidence for each of these molecules
Subject(s)
Animals , Light Signal Transduction/physiology , Photoreceptor Cells, Invertebrate/physiology , Second Messenger Systems/physiology , Calcium Channels/physiology , Cyclic GMP/physiology , Inositol 1,4,5-Trisphosphate/physiologyABSTRACT
Odorant detection takes place at the receptor neurons of the olfactory epithelium and odorant discrimination relies in an important degree on these chemosensory cells. Here we review the evidence for the participation of multiple transduction pathways in the mechanisms of odor recognition in olfactory neurons