Project description:Alkali stress is an important means of inactivating undesirable pathogens in a wide range of situations, ranging from environmental cleaning of food processing environments, to the phagolysosomal killing of cells engulfed by mammalian phagocytes. Unfortunately, L. monocytogenes can launch an alkaline tolerance response (AlTR), significantly increasing persistence of the pathogen in such environments. This study compared the transcriptome patterns of alkali stressed and non alkali stressed L. monocytogenes 10403S cells, to elucidate the mechanisms by which this important pathogen adapts and/or grows during short or long-term alkali stress. Transcription profiles associated with alkali shock (AS) responses were obtained by DNA microarray analysis of mid-exponential cells suspended in pH 9 media for 15, 30 or 60 min. Transcription profiles associated with alkali adaptation (AA) were obtained by DNA microarray analysis of cells grown to mid-exponential phase in pH 9 media . Comparison of AS and AA transcription profiles with profiles from control (pH 7.0) cells identified over 2,000 genes that were differentially expressed under alkaline conditions. Rapid (15min) changes in expression included upregulation of genes encoding for multiple metabolic pathways, (including those associated with Na+/H+ antiporters), ABC transporters of functional compatible solutes such as carnitine, motility and virulence-associated genes as well as the σB controlled stress resistance network. Slower (30min and more) responses to AS and adaptation during growth in alkaline conditions (AA), included modest changes in mRNA concentrations, and genes involved in proton export. Keywords: Time course study of gene expression response to alkaline shock and adaptation
Project description:To investigate possible genetic basis of alkali tolerance in rice, we generated an introgressed rice line (K83) with significantly enhanced tolerance to alkali stress than its recipient parental cultivar (Jijing88). By using microarray analysis, we examined global gene expression profiles in K83 and Jijing88, found more than 1,200 genes were constitutively differentially expressed in K83 compared with Jijing88, with 572 up- and 654 down-regulated. Upon alkali treatment, a total of 347 genes in K83 were found up- and 156 down-regulated in K83, compared with 591 and 187 respectively in Jijing88. Seven-day-old uniform-sized seedlings grown in hydroponic medium were transferred to fresh hydroponic medium alone or containing 50 mM alkali salts. Shoots were harvested 24 h after transfer and 10 shoots were pooled for microarray analysis.
