Characterization of Defensive Response Influenced by Volatile Oxylipin in ArabidopsisCharacterization of Defensive Response Influenced by Volatile Oxylipin in Arabidopsis

Abstract

Oxylipins are oxygenated natural products derived from fatty acids and widespread in aerobic organisms such as plant, animal and fungi. The important function of these compounds in plant is the regulation of many defense responses and developmental processes. However, although the role of JA in defense responses and signalling, and cross-talk between JA and other signal molecules such as salicylic acid (SA), ethylene (ET) and abscisic acid (ABA) have been extensively investigated in plant, other oxylipins including cis-3-hexenal presented in most plants and 1-octen-3-ol known as fungal oxylipin discovered in some plants have not been fully investigated at molecular level. Thus, in this study, we focused on identification of transcriptional responses in Arabidopsis after treatment of cis-3-hexenal and 1-octen-3-ol to understand defense response and signal transduction by them. As the results, transcriptional responses by vapor treatments of oxylipin, 3-hexenal and 1-octen-3-ol, in Arabidopsis were identified through microarray analysis, and total numbers of 414 and 547 genes were up- or down- regulated more than 2 folds in the treatments of each 3-hexenal and 1-octen-3-ol, respectively. About 30% of those genes 124/414 genes in 3-hexenal treatment and 167/547 genes in 1-octen-3-ol, were related to biotic/abiotic responses. In the clustering of expression patterns, genes related to biotic/abiotic responses revealed two representative patterns, up-regulation consistently during 24 hr or progressive increase until 12 hr time point in each treatment of 3-hexenal and 1-octen-3-ol. Furthermore, the genes related to biotic/abiotic responses were mapped into biotic stress pathway regarding to R and PR genes, hormone (auxins, ABA, ethylene and JA) signaling, cell wall, proteolysis, redox state, peroxidases, glutathione-S-transferase, signaling, MAPK, transcription factors (ERFand WRKY), heat shock proteins and secondary metabolism. The number of genes mapped into biotic stress pathway was 85 of 414 genes (about 20%) and 117 of 547 genes. Interestingly, almost of genes up- or down- regulated more than two folds in each 3-hexenal and 1-octen-3-ol treatment were overlapped, and rate of overlapping genes was more than 85% in up-regulated genes, and more than 60% in down-regulated genes. Based on these results, it was assumed that when plant recognizes 3-hexenal or 1-octen-3-ol, various biotic stress genes including R and PR genes, hormone signaling, redox state, cell wall, proteolysis, signaling, and transcription factors related genes might be up-regulated during 12 hr to increase defense system in the cell.