Genes and signaling pathways involved in silicon-induced resistance (SI-ISR) of tomato against Ralstonia solanacearum

Silicon (Si) treatment induced resistance in tomato against bacterial wilt caused by Ralstonia solanacearum. Analyzing the gene expression of defense-related genes by quantitative real time PCR (qRT-PCR), up-regulation of JERF3, TSRF1, ACCO, FD-I, POD and AGP-1g in Si-amended, but not in untreated plants was observed after challenging with the pathogen. These genes play a role in ethylene (ET) and jasmonic acid (JA) signalling pathways. Gene expression was generally highest at 72 hours post inoculation. At this time point gene expression analysed by the TOM2 microarray revealed sixteen genes significantly regulated by Si in plants treated with Si challenged with R. solanacearum compared to plants without Si application. The microarray results were validated by qRT-PCR, and the genes were annotated and functionally classified. At least twelve genes involved in defense, signal transduction, response to stresses, transcription, ubiquitinylation and metabolism were up-regulated. Highest up-regulation of 11.0 log sub(2) fold was found with the tify (ZIM)-protein JAZ1, involved in regulation of the JA-signalling pathway. A role of Si in priming the defense capacity of the plant involving reactive oxygen species (ROS), ET and JA signalling pathways and thereby alleviating biotic stress imposed by the pathogen is suggested.