RESUMO
Cherry tomato Solanum lycopersicum var cerasiforme cv Matt's wild cherry is a very resistant cultivar to most Phytophthora infestans isolates. Two isolates were identified, US940480 and US970001 that cause an incompatible and a compatible interaction respectively. US970001 is one of the few isolates producing a compatible interaction with this cultivar. To identify genes with a differential gene expression between compatible and incompatible interactions, gene expression patterns were analyzed with tomato cDNA microarrays including 12,899 independent tomato cDNA clones at different time points after inoculation. A diverse set of statistical tools were used to identify key components of the plant response to the pathogen. Forty-three genes were up-regulated during the incompatible reaction at time point 36 hours, 15 globally at all time points and twelve were found both in globally and at 36 hours. Northern blots analysis was performed to confirm differential expression showed by microarray analysis and to study the differential expression of more plant resistance genes (PR) genes between compatible and incompatible interactions for this interaction.
El tomate cherry Solanum lycopersicum var cerasiforme cv Matt's es bastante resistente a la gran parte de aislamientos de Phytophthora infestans. Se han identificado dos aislamientos, US940480 y US970001 que causan interacción incompatible y compatible respectivamente. US970001 es uno de los pocos aislamientos causantes de interacción compatible con este cultivo. Con el fin de identificar genes con expresión diferencial en interacciones compatible e incompatible, analizamos DNA copia de 12899 clones independientes en tres tiempos posteriores a la inoculación del patógeno. Se aplicaron diversas herramientas estadísticas para identificar componentes moleculares claves de la respuesta de la planta al patógeno. Cuarenta y tres genes fueron detectados como activados durante la interacción incompatible a las 36 horas posinoculación, 15 genes se detectaron como activados globalmente tomando en conjunto los 3 tiempos analizados y 12 genes tanto globalmente como a las 36 horas. Análisis de Northern blot permitieron confirmar la expresión diferencial detectada con los análisis de microarreglos y estudiar la expresión diferencial de otros genes de resistencia en plantas (PR) en in teracciones compatible e incompatible en esta interacción.
RESUMO
In order to understand the genetic responses resulting from physiological changes that occur in plants displaying citrus variegated chlorosis (CVC) symptoms, we adopted a strategy of comparing two EST libraries from sweet orange [Citrus sinensis (L.) Osbeck]. One of them was prepared with plants showing typical CVC symptoms caused by Xylella fastidiosa and the other with non-inoculated plants. We obtained 15,944 ESTs by sequencing the two cDNA libraries. Using an in silico hybridization strategy, 37 genes were found to have significant variation at the transcriptional level. Within this subset, 21 were up-regulated and 16 were down-regulated in plants with CVC. The main functional categories of the down-regulated transcripts in plants with CVC were associated with metabolism, protein modification, energy and transport facilitation. The majority of the up-regulated transcripts were associated with metabolism and defense response. Some transcripts associated with adaptation to stress conditions were up-regulated in plants with CVC and could explain why plants remain alive even under severe water and nutritional stress. Others of the up-regulated transcripts are related to defense response suggesting that sweet orange plants activate their defense machinery. The genes associated with stress response might be expressed as part of a secondary response related to physiological alterations caused by the infection.