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).

Copper tolerant brown rot fungi are able to depolymerize the structure of wood treated with copper or organic wood preservatives. This research used quantitative polymerase chain reaction (qRT-PCR) combined with RNA-seq to explore what genes of the brown-rot fungus, Fibroporia radiculosa, are expressed when the fungus is overcoming the wood preservatives and decaying the wood. The preliminary study of ACQ-treated wood indicated that the hydrogen peroxide needed for wood decay to proceed may come from AAOX (aryl alcohol oxidase), with oxalate regulation by ODC2 (oxalate decarboxylase), and copper regulation by COP (copper resistance P-type ATPase pump). The principal study measured the expression of ten genes at early, mid, and late stages of decay in wood treated with azole, copper, quat, ACQ, CA, plus untreated. Both AAOX and LCC (laccase) were often expressed at their highest levels early in the decay stages, thus either one or both could be involved in early Fenton chemistry. Expression levels of ICL (isocitrate lyase) and GLOXDH (glyoxylate dehydrogenase) were also highest in early decay stages. Of great interest was the complete lack of expression of the COP gene on copper-treated wood at any decay stage. The most surprising and significant result is the impact the quat-treatment had on the metabolism of the fungus, and lack of impact of the azole-treatment. This research indicates that it is the quat that provides the greatest inhibition of F. radiculosa, more so than the copper. Based on RNA Seq, the total number of genes that were up- or down-regulated on the copper-treatment was 473, with 293 on the quat-treatment, and 185 on the azole-treatment. There were a number of genes with unknown protein functions highly expressed. These data distinctly show that gene expression profiles of F. radiculosa are altered by different wood preservative compositions and the duration of wood decay. These genes and this data needs further analysis and study in order to meet the long term goal of understanding the mechanism of copper-tolerance inFibroporia radiculosa.