RESUMEN
Erwinia carotovora subsp. atroseptica is responsible for potato blackleg disease in the field and tuber soft rot during crop storage. The process leading to the disease occurs in two phases: a primary invasion step followed by a maceration step. Bacteria-to-bacteria communication is associated with a quorum-sensing (QS) process based on the production of N-acylhomoserine lactones (HSL). The role of HSL throughout plant infection was analyzed. To this purpose, HSL produced by a specific E. carotovora subsp. atroseptica wild-type strain, which was particularly virulent on potato, were identified. A derivative of this strain that expressed an HSL lactonase gene and produced low amounts of HSL was generated. The comparison of these strains allowed the evaluation of the role of HSL and QS in disease establishment and development. Bacterial growth and motility; activity of proteins secreted by type I, II, and III systems; and hypersensitive and maceration reactions were evaluated. Results indicated that HSL production and QS regulate only those traits involved in the second stage of the host plant infection (i.e., tissue maceration) and hypersensitive response in nonhost tobacco plants. Therefore, the use of QS quenching strategies for biological control in E. carotovora subsp. atroseptica cannot prevent initial infection and multiplication of this pathogen.
Asunto(s)
4-Butirolactona/análogos & derivados , 4-Butirolactona/metabolismo , Pectobacterium carotovorum/metabolismo , Regulación Bacteriana de la Expresión Génica , Silenciador del Gen , Genes Bacterianos , Datos de Secuencia Molecular , Pectobacterium carotovorum/genética , Enfermedades de las Plantas/microbiología , Solanum tuberosum/microbiología , Nicotiana/microbiología , VirulenciaRESUMEN
The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level.
Asunto(s)
Acil-Butirolactonas/metabolismo , Regulación de la Temperatura Corporal/fisiología , Regulación Enzimológica de la Expresión Génica , Ligasas/metabolismo , Pectobacterium/fisiología , Percepción de Quorum/fisiología , Secuencia de Bases , Cartilla de ADN , Ligasas/genética , Datos de Secuencia Molecular , Enfermedades de las Plantas/microbiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Análisis de Secuencia de ADN , Solanum tuberosum/microbiología , TemperaturaRESUMEN
Erwinia carotovora subsp. atroseptica and Erwinia carotovora subsp. carotovora can cause substantial damage to economically important plant crops and stored products. The occurrence of the disease and the scale of the damage are temperature dependent. Disease development consists first of active multiplication of the bacteria in the infection area and then production of numerous extracellular enzymes. We investigated the effects of various temperatures on these two steps. We assayed the specific growth rate and the pectate lyase and protease activities for eight strains belonging to E. carotovora subsp. atroseptica and E. carotovora subsp. carotovora in vitro. The temperature effect on growth rate and on pectate lyase activity is different for the two subspecies, but protease activity appears to be similarly thermoregulated. Our results are in agreement with ecological data implicating E. carotovora subsp. atroseptica in disease when the temperature is below 20 degrees C. The optimal temperature for pathogenicity appears to be different from the optimal growth temperature but seems to be a compromise between this temperature and temperatures at which lytic activities are maximal.