Four Fibroporia radiculosa isolates undergoing decay of untreated and 1.2% ammoniacal copper citrate treated wood were evaluated for differential expression of citrate synthase (CS), isocitrate lyase (ICL), glyoxylate dehydrogenase (GLOXDH), succinate/fumarate antiporter (ANTI), and a copper resistance-associated ATPase pump (ATPase). Samples were analyzed at 2, 4, 6, and 8 weeks for oxalate and protein production, enzyme activities, and gene expression. ATPase pump expression was increased in the presence of copper when initial oxalate concentrations were low, suggesting it functions in helping the fungus adapt to the copper-rich environment by pumping toxic copper ions out of the cell. A connection in expression levels between CS, ANTI, ICL, and GLOXDH for the four isolates was found suggesting the production of oxalate originates in the mictochondrial TCA cycle (CS), shunts to the glyoxysomal glyoxylate cycle (ANTI), moves through a portion of the glyoxylate cycle (ICL), and ultimately is made in the cytoplasm (GLOXDH).