Fine-scale cation dynamics and control by Rhodonia placenta and Pleurotus ostreatus during wood decay

Anderson, Claire E.; Castaño, Jesús D.; Schilling, Jonathan S.

doi:10.1016/j.ibiod.2023.105643

Cited by 2 publications

(2 citation statements)

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“…Brown rot fungi use a ROS-dependent, metal- and LMW metabolite-mediated oxidative mechanism to kick off wood degradation ( 16 , 34 , 40 ). Subsequently, the released oligosaccharides are hydrolyzed with glycoside hydrolases ( 6 , 16 ).…”

Section: Resultsmentioning

confidence: 99%

“…The early stage of brown rot is often accompanied by the fungal-amended increases in the levels of H + and metal availability that are boosted by the secretion of organic acids (e.g., oxalic acid), the elevated oxidative potentials caused by the production of ROS, and other environmental traits that can allow oxidative attacks on wood substrates ( 40 , 47 – 50 ). These environmental changes not only act as signals to trigger fungus’ physiological responses ( 35 , 51 ), but they could also interact with fungal enzymes via controlling the reaction conditions or modifying the functional groups in proteins ( 52 – 55 ).…”

Section: Resultsmentioning

confidence: 99%

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Unlocking the distinctive enzymatic functions of the early plant biomass deconstructive genes in a brown rot fungus by cell-free protein expression

Castaño,

El Khoury,

Goering

et al. 2024

Appl Environ Microbiol

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Saprotrophic fungi that cause brown rot of woody biomass evolved a distinctive mechanism that relies on reactive oxygen species (ROS) to kick-start lignocellulosic polymers’ deconstruction. These ROS agents are generated at incipient decay stages through a series of redox relays that shuttle electrons from fungus’s central metabolism to extracellular Fenton chemistry. A list of genes has been suggested encoding the enzyme catalysts of the redox processes involved in ROS’s function. However, navigating the functions of the encoded enzymes has been challenging due to the lack of a rapid method for protein synthesis. Here, we employed cell-free expression system to synthesize four redox or degradative enzymes, which were identified, by transcriptomic data, as conserved players of the ROS oxidation phase across brown rot fungal species. All four enzymes were successfully expressed and showed activities that enable confident assignment of function, namely, benzoquinone reductase (BQR), ferric reductase, α-L-arabinofuranosidase (ABF), and heme-thiolate peroxidase (HTP). Detailed analysis of their catalytic features within the context of brown rot environments allowed us to interpret their roles during ROS-driven wood decomposition. Specifically, we validated the functions of BQR as the driver redox enzyme of Fenton cycles and reconstructed its interactions with the co-occurring HTP or laccase and ABF. Taken together, this research demonstrated that the cell-free expression platform is adequate for synthesizing functional fungal enzymes and provided an alternative route for the rapid characterization of fungal proteins, escalating our understanding of the distinctive biocatalyst system for plant biomass conversion. IMPORTANCE Brown rot fungi are efficient wood decomposers in nature, and their unique degradative systems harbor untapped catalysts pursued by the biorefinery and bioremediation industries. While the use of “omics” platforms has recently uncovered the key “oxidative-hydrolytic” mechanisms that allow these fungi to attack lignocellulose, individual protein characterization is lagging behind due to the lack of a robust method for rapid synthesis of crucial fungal enzymes. This work delves into the studies of biochemical functions of brown rot enzymes using a rapid, cell-free expression platform, which allowed the successful depictions of enzymes’ catalytic features, their interactions with Fenton chemistry, and their roles played during the incipient stage of brown rot when fungus sets off the reactive oxygen species for oxidative degradation. We expect this research could illuminate cell-free protein expression system’s use to fulfill the increasing need for functional studies of fungal enzymes, advancing the discoveries of novel biomass-converting catalysts.

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