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item Horvath, David
item Anderson, James

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/28/2004
Publication Date: 2/7/2005
Citation: Horvath, D.P., Anderson, J.V. 2005. Microarray analysis of dormancy breaking in underground buds of leafy spurge (Euphorbia esula).[Abstract]. Weed Science Society of America. Page No. 67.

Interpretive Summary: We have used a collection of sequenced clones of expressed genes (ESTs) from the perennial weed leafy spurge and cassava, a related crop species, to develop a tool called microarrays. Microarrays are simply microscope slides upon which a collection of as many as 30,000 different clones have been spotted. These microarrays serve as a platform for observing changes in expression of each of the different genes following treatments. In our case, we have studied the changes in gene expression from approximately 2500 different genes in the buds of leafy spurge as they were induced to grow following loss of the aerial portion of the plant. We identified a number of genes with expression levels that were specifically induced or repressed following growth induction. One gene of particular interest appears to have some function in regulating the expression of other genes and/or altering the physiological state of the buds was induced within 12 hours following treatment.

Technical Abstract: Abstract: Many weeds depend on growth of underground shoots to avoid control measures such as herbicide treatments or tillage. It would be a great benefit to land users if signals regulating growth of these underground buds could be exploited. Growth could be inhibited following herbicide treatments or tillage, or induced prior to such treatments or at the end of the growing season to reduce the density of the bud bank. The best way to identify these growth regulating signals and gain an understanding of their mechanisms of action is to identify genes that are responsive to them. Currently, the use of microarray technology offers the best hope for identifying such genes. Thus, we have developed cDNA microarrays from a small EST database from a cDNA library of growing underground buds of leafy spurge. The microarrays each contain 1887 leafy spurge clones (representing nearly 1500 different genes) spotted in triplicate. The arrays also contain approximately 400 different cassava cDNA clones as well as clones for control genes from other plants, animals and bacteria all spotted at least twice on each array. The arrays were hybridized to RNA from leafy spurge root buds collected at 0, 12hr, 24hr, 48hr, and 72hr after defoliation (a treatment known to induce root bud growth and development). A dye swap design using biological replication of the time points was used to reduce the number of false positives/negatives. From these experiments, we identified genes that were specifically up and down regulated following growth induction. However, one gene, represented by a cDNA with some homology to a ser/thr protein kinase from maize, was rapidly and transiently up regulated. The expression pattern of this gene was confirmed by northern analysis. An Arabidopsis orthologue of this gene is specifically regulated by circadian rhythm and by conditions which suppress certain cell wall associated receptor kinases. Work is underway to clone full length cDNA and genomic clones representing this gene, and to further study the expression of this gene in leafy spurge. Unfortunately, the limited number of genes on this preliminary array reduced our ability to identify likely signal transduction pathways based on clusters of genes with recognized functions/regulation. A more robust microarray from the whole plant EST database is planned pending funding.