Defeating copper tolerance: an example of how “omics” research can accelerate discovery of new wood protection compounds
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In: Proceedings, American wood protection association annual meeting 2016. San Juan, PR: Vol. 112. 106-113.
Imagine if you could measure all the genes being expressed at any one time in an organism and you knew what all the genes did in a cell. The power of this knowledge would allow you to determine how organisms regulate gene activity to survive. This is the essence of how “omics” science accelerates biological understanding. From a wood protections standpoint, understanding which genes regulate copper tolerance effectively identifies metabolic chokepoints that would have the highest likelihood of interfering with copper tolerance. Thus, the search for copper co-biocides is no longer random, but instead, follows a rational process, guided by knowledge of which steps in metabolism are being differentially regulated for survival on substrates containing copper. We used this rational process to identify to potential inhibitors that might defeat copper tolerance: pyraclostrobin (a member of the strobilurin family of fungicides) and salicylhydroxamic acid (SHAM). The strobilurins and SHAM disrupt different steps in mitochondrial respiration, a metabolic pathway we found to be up-regulated with biosynethesis of oxalate in our omics analysis. Oxalate is the molecule that has a direct role in removing copper toxicity by trapping the copper in an insoluble copper oxalate crystal. In accordance with our hypothesis, the triple combination of 5000 µg/mL copper sulfate, 4 or 8 µg/mL pyraclostrobin, and 100 µg/mL SHAM completely inhibited growth compared to compounds tested alone over a 20-day observation period in agar plate studies with the copper-tolerant fungus, Fibroporia radiculosa. Results from AWPA E22 soil block tests, which uses percent compression strength loss as a measure of decay, were also promising when tested against F. radiculosa and another copper-tolerant species, Fomitopsis palustris. Using above ground retentions for copper ethanolamine, the triple combination wood treatment (copper, pyraclostrobin, and SHAM) performed much better than copper ethanolamine alone, and performed as well or better than wood treated with our reference, the above ground retention for ACQ-D. With over 900 potential targets or genes that showed differential regulation for survival on copper, it is our hope that co-biocide discovery will no longer be the bottleneck in wood preservative development.
KeywordsCopper tolerance; co-biocide; strobilurin; decay fungi; salicylhydroxamic acid
Tang, Juliet D.; Ciaramitaro, Tina; Nicholas, Darrel D.; Tomaso-Peterson, Maria; Diehl, Susan V. 2017. Defeating copper tolerance: an example of how “omics” research can accelerate discovery of new wood protection compounds. In: Proceedings, American wood protection association annual meeting 2016. San Juan, PR. 112. 106-113.