|Klein, Robert - Bob|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2005
Publication Date: 5/1/2005
Citation: Salzman, R.A., Brady, J.A., Finlayson, S.A., Buchanon, C.D., Sun, F., Klein, P.E., Klein, R.R., Pratt, L.H., Cordonnier-Pratt, M.M., Mullet, J.E. 2005. Transcription profiling in response to methyl jasmonate salicylic acid, and aminocyclopropane carboxylic acid reveals cooperative gene regulation and novel components implicated in plant defense. Plant Physiology. 138:352-368. Interpretive Summary: Major advancements in science hinge on the development of new tools including gene microarrays. Microarrays are small glass slides onto which portions of thousands of genes can be spotted. Genes are tiny packets of genetic blueprint material that are found inside the cells of all plants and animals and control all of the physical characteristics of these organisms. Our work focuses on improving major grain crops, and with an understanding how all genes are regulated, the genetic blueprint will be visible and this information can make improving the plants more efficient. This study details the expression of thousands of plant genes and reveals which genes respond to defend plants against disease. The simultaneous examination of the expression of thousands of genes will permit more efficient identification of defense-response genes, and will facilitate a better understanding of how all these genes are regulated in an orchestrated manner. Information will be primarily used by fellow scientists but the work should ultimately result in better adapted, higher producing crop varieties available to American farmers.
Technical Abstract: We have conducted a large-scale study of gene expression in the monocot Sorghum bicolor in response to the defense signaling compounds salicylic acid and methyl jasmonate, and the ethylene precursor aminocyclopropane tissue, and at 3 and 27 hours, using a newly developed microarray containing 16,801 non-redundant elements. Data from 102 slides and quantitative real time PCR data on mRNA abundance from 250 genes were collected and analyzed. Numerous gene clusters were identified in which expression was correlated with particular defense compound by tissue combinations. Many genes previously implicated in defense responded to the treatments, including numerous PR genes and most members of the phenylpropanoid pathway. Further, a group of endoxylanase inhibitors implicated in monocot defense responses was identified, as were several genes that may represent novel defense activities or pathways. Genes of the octadecanoic acid pathway of jasmonic acid synthesis were induced by salicylic acid as well as by methyl jasmonate. The resulting hypothesis that increased salicylic acid could lead to increased endogenous jasmonic acid production was confirmed by measurement of jasmonic acid content. Comparison of responses to salicylic acid, methyl jasmonate, and combined salicylic acid plus methyl jasmonate revealed patterns of one-way and mutual antagonisms, as well as synergistic effects on regulation of some genes. These experiments thus help further define the transcriptional results of cross talk between the salicylic acid and jasmonic acid pathways, and suggest that a subset of genes coregulated by salicylic acid and jasmonic acid may comprise a uniquely evolved sector of the plant defense arsenal.