Comparison of gene expression profiles in Bacillus megaterium treated tobacco leaves using microarray

The MP agent, prepared from Bacillus megaterium isolated from the soil near tobacco fields, can improve metabolic products, and hence the aroma, of tobacco (Nicotiana tabacum) leaf. To explore genes regulating metabolic responses in tobacco leaf, we used microarrays to analyze differentially expressed genes in tobacco leaves subjected to various treatments. The expressed genes were classified into six groups based on their expression profile. In total, 753 genes were significantly differentially expressed between microorganism-treated and water-treated samples. Gene ontology (GO) analyses showed that most of these genes were involved in metabolic and cellular processes. Some upregulated genes were related to the plant defense response, such as NtMMP1 and NtACRE231. Some genes were involved in metabolism responses, such as NtDXS. Semi-quantitative reverse transcriptase (RT)-PCR analysis of NtMMP1 and quantitative RT-PCR analysis of NtDXS showed that their expression levels increased after MP agent treatment, confirming the microarray results. We evaluated NtMMP1 and NtDXS in terms of their associations with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Phylogenetic analyses of NtMMP1, NtACRE231, and NtDXS revealed their relationships with homologs in other species. These microarray data increase our understanding of the mechanisms by which MP agent induces a metabolic response in tobacco leavesKey words: Nicotiana tabacum, Microarray, MP agent, plant defense response, aroma