Abstract
The capacity of white-rot fungi to degrade wood lignin may be highly applicable to the development of novel bioreactor systems, but the mechanisms underlying this function are not yet fully understood. Lignin peroxidase (LiP) and manganese peroxidase (MnP), which are thought to be very important for the ligninolytic property, demonstrated increased activity in Phanerochaete chrysosporium RP-78 (FGSC #9002, ATCC MYA-4764™) cultures following exposure to 5 mM cyclic adenosine 3', 5'-monophosphate (cAMP) and 500 μM 3'-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that transcription of most LiP and MnP isozyme genes was statistically significantly upregulated in the presence of the cAMP and IBMX compared to the untreated condition. However, 100 μM calmodulin (CaM) inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), which had insignificant effects on fungal growth and intracellular cAMP concentration, not only offset the increased activity and transcription induced by the drugs, but also decreased them to below basal levels. Like the isozyme genes, transcription of the CaM gene (cam) was also upregulated by cAMP and IBMX. These results suggest that cAMP signaling functions to increase the transcription of LiP and MnP through the induction of cam transcription.
Highlights
White-rot fungi are known to have a powerful ligninolytic system that can completely degrade wood lignin (Kirk and Farrell 1987,; Kirk et al 1975,) as well as persistent organic pollutants such as dioxin (Bumpus et al 1985,)
lignin peroxidase (LiP) and manganese peroxidase (MnP) activity levels statistically significantly increased in the presence of 5 mM cAMP and 100 μM IBMX compared to the no-supplement control (Figure 2)
These results suggest that the cAMP pathway has a positive effect on LiP and MnP expression that can be blocked by CaM inhibition
Summary
White-rot fungi are known to have a powerful ligninolytic system that can completely degrade wood lignin (Kirk and Farrell 1987,; Kirk et al 1975,) as well as persistent organic pollutants such as dioxin (Bumpus et al 1985,). This ability may be applicable to the construction of a novel potent bioreactor system to convert wood to potent materials and energy sources with low environmental load and to bioremediate polluted environments. LiP and MnP themselves have potential applications in treating textile effluent (Sedighi et al 2009,; Singh et al 2010) Their expression is inductive, related to unknown factors, and known to be unstable, as is the entire ligninolytic system. Information concerning the LiP and MnP expression system is highly important and requisite for better understanding the expression of the entire ligninolytic system, and for molecular breeding of high LiP- and/or high MnP-producing strains
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