Transcriptomic analysis of salicylic acid-responsive genes in tobacco by-2 cells

Tobacco has played historically important role in the discovery and functional analysis of salicylic acid (SA) as a plant hormone. Using this model, it was demonstrated for the first time that tobacco mosaic virus (TMV) infection results in the accumulation of SA in infected tissues that is to activate local and systemic expression of pathogenesis-related proteins in the cells. Furthermore, SA has been shown to function as a major factor in the development of systemic acquired resistance (SAR) in plants. To promote the importance of tobacco as a model plant, we generated and sequenced cDNA libraries from tobacco BY-2 cells, depositing about 20,000 EST sequence information in the public databases. Selected cDNA clones were then used to prepare the first large-scale 16K microarray of tobacco. In this chapter, we describe our results of a large scale gene expression analysis, using the tobacco BY-2 cells, treated with a 40 μM salicylic acid. In total, 376 genes (corresponding to individual ESTs) were at least 2-fold upregulated by SA, relative to their expression levels in control cells. Amid, a large number of genes overlapped with known defense-related genes in plants, whilst the others represented novel targets of SA in plants. The kinetic analysis of the SA-responsive genes, together with functional analysis of these genes in the plant defense, is presented in this chapter.