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Applied and Environmental Microbiology, September 1998, p. 3536-3538, Vol. 64, No. 9
Department of Microbiology, University of
Stellenbosch, Stellenbosch, 7600 South Africa,1
and
Institute of Microbial and Biochemical Technology,
Received 20 April 1998/Accepted 23 June 1998
Expression of Phanerochaete chrysosporium genes
encoding ligninolytic enzymes was assessed in wood. Poly(A) RNA was
extracted from colonized wood chips by magnetic capture, and specific
transcripts were quantified by competitive reverse transcriptase PCR.
mRNA levels varied substantially among lignin peroxidase genes, and transcript patterns were dramatically different from those in previous
studies with defined media.
Lignin depolymerization is catalyzed
by extracellular enzymes of white rot basidiomycetes such as
Phanerochaete chrysosporium. Major components of this system
include lignin peroxidases (LiPs), manganese-dependent lignin
peroxidases (MnPs), and a peroxide-generating enzyme, glyoxal oxidase
(GLOX) (for review, see references 6, 11, and
17). Under nutrient limitation in defined media,
multiple peroxidase and GLOX isozymes are secreted.
The peroxidases of P. chrysosporium are encoded by families
of structurally related genes. Ten LiP genes, designated
lipA through lipJ, have been characterized and
shown to be distributed on three linkage groups (reviewed in reference
12). The three known MnP genes (mnp
genes) are unlinked to each other or to any LiP genes (reference
28 and unpublished data). In contrast, GLOX is
encoded by a single gene (glx) with two alleles (20, 23). The precise roles and interactions of these genes in lignin degradation and in commercial processes such as biomechanical pulping
(for review, see reference 24) are poorly
understood.
Numerous studies have demonstrated differential regulation of LiP and
MnP genes in response to culture conditions. Northern blots showed
lipD transcripts dominating in carbon-starved cultures (18) and in defined media supplemented with balled-mill
straw (19). In contrast, lipA transcripts were
relatively more abundant in nitrogen-limited media (18).
Nuclease protection assays identified lipE as the major
transcript in both carbon- and nitrogen-starved cultures
(30). Quantitative reverse transcriptase-mediated PCR (RT-PCR) techniques largely confirmed Northern blots and also showed
dramatic upregulation of lipC and lipJ under
nitrogen starvation (31). All LiP gene transcripts except
lipF were detected in anthracene-contaminated soil cultures
(3). The MnP genes of P. chrysosporium exhibit
complex regulation by nutrient limitation (15, 29), Mn
concentration (7, 9, 14), culture agitation, heat shock
(8), H2O2 concentration, and other
chemical stresses (25). mnp3 appears not to be
regulated by Mn. In contrast, mnp1 and mnp2
respond strongly to Mn and are differentially regulated in response to
culture agitation (15). The three MnP genes are coordinately
transcribed in soil cultures (4). Nothing is known of the
regulation of P. chrysosporium peroxidase genes in woody tissue, the natural substrate.
To assess transcript levels of all known LiP, MnP, and GLOX genes in
P. chrysosporium-colonized wood, 2.5 kg of aspen wood chips
was steam sterilized and inoculated by standard biomechanical pulping
methods (1) (reviewed in reference 2).
Poly(A) RNA was extracted from 10-g samples as described elsewhere
(32), with minor modifications. Specifically, the initial
extract buffer was squeezed through Miracloth (Calbiochem, Inc., La
Jolla, Calif.) filters, and following incubation with Dynabeads
oligo(dT)25 (Dynal, Great Neck, N.Y.), the hybridization
buffer was twice extracted with a model MPC-1 magnetic concentrator.
Poly(A) RNA levels were too low to accurately quantify (<1 µg/10 g),
but yields were adequate for a minimum of 600 separate RT-PCRs. The
competitive RT-PCR protocol was adapted from the work of Gilliland et
al. (16) with gene-specific primers (Table
1). Competitive templates, in the form of
full-length genomic subclones, were added to 50-µl PCR mixtures as
10-fold serial dilutions ranging from 10 ng to 0.1 fg. Preliminary
experiments quantifying lipA, lipC,
lipE, and lipF transcripts with various amounts
of poly(A) template in RT-PCRs showed no evidence for RT inhibition
(10).
PCR products were size fractionated on 1.5% agarose gels and ethidium
bromide stained, and the image was recorded with a Foto/Analyst digital
camera (Fotodyne, Inc., Hartland, Wis.). The image was digitized with
NIH Image software (version 1.61). Linear regressions were determined
by plotting ratios of genomic competitor to cDNA target against the
concentration of competitive template. Adjusting for length
differences, equivalence points were determined on linear regressions
where the ratios were 1.5 for lip genes, 1.3 for
mnp genes, and 1.19 for glx. Results were
expressed in picograms of cDNA (Fig. 1).
Independent analysis for lipC and mnp2 transcript levels in separate wood chip cultures varied less than 12%.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Expression of Phanerochaete
chrysosporium Genes Encoding Lignin Peroxidases, Manganese
Peroxidases, and Glyoxal Oxidase in Wood
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ABSTRACT
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TEXT
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Abstract
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References
TABLE 1.
Competitive PCR primers

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FIG. 1.
Competitive PCRs comparing transcripts of three genes in
samples collected after 2 and 8 weeks of incubation. Vertical arrows
represent approximate equivalence points. Digitized images were
acquired and labeled with Adobe Photoshop 3.0 and Illustrator 7.0, respectively. Numbers at right indicate molecular size in base pairs.
Differences in transcript levels ranged up to 10,000 fold (Fig. 2), and transcript patterns in aspen were unlike the patterns previously observed in defined media or in soil cultures. Transcripts of lipF, absent in soil cultures, were abundant. lipD and lipE, major transcripts in soil and defined media, ranked lowest among LiP gene transcripts in aspen. Transcripts of lipI, represented by a single functional allele (lipI1) in dikaryotic strain BKM-F-1767, were at high levels relative to those in defined media (31). (The alternative allele, lipI2, is transcriptionally inactive due to insertion of a repetitive element [13].) Relative to lip genes, the mnp genes showed less difference in transcript levels.
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The identification of glx transcripts in wood was consistent with a close physiological connection between extracellular peroxidases and GLOX (21, 22). The simultaneous detection of lip and glx transcripts was reported in defined media (20, 23) and in soil cultures (3).
Transcript levels generally declined by 8 weeks of incubation, although it is unclear whether transcription was reduced or whether mRNA was partially degraded. lipA and glx transcripts decreased more than 100-fold, while lipB, lipE, and lipF transcripts increased 3- to 4-fold. Temporal shifts in transcription have been observed in defined media (3, 5, 25).
No clear relationship between genomic organization and transcription emerges from these and previous results. Within the two LiP gene clusters (lipA, lipB, lipC, lipE and lipI, lipG, lipH, lipJ), no patterns are evident. The unlinked LiP genes, lipD and lipF, show patterns very different from those of one another and from those of most other lip genes. In comparing all genes on all substrates, lipD and lipE transcript patterns are most alike, although the lipD transcript levels are consistently 5- to 10-fold higher than those of lipE.
The substantial differences in transcript levels probably reflect enzyme activity in aspen, as has been demonstrated in defined media (5, 26, 27) and in soil cultures (3, 4). Thus, genes previously shown to be highly expressed under a wide range of cultural conditions, such as lipD and lipE (18, 19, 30), are unlikely to play a major role in biopulping performance on aspen. It remains to be determined if these genes are differentially regulated under other conditions (e.g., wood species, temperature, and moisture).
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ACKNOWLEDGMENTS |
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This research was supported by grant DE-FG02-87ER13712 from the U.S. Department of Energy to D.C. B.J.H.J. was supported by grants from the Foundation for Research Development (South Africa) and Mondi Kraft (South Africa).
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FOOTNOTES |
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* Corresponding author. Mailing address: USDA Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53705. Phone: (608) 231-9468. Fax: (608) 231-9488. E-mail: dcullen{at}facstaff.wisc.edu.
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REFERENCES |
|---|
|
|
|---|
| 1. | Akhtar, M. April 1997. U.S. Patent 5,620,564. |
| 2. | Akhtar, M., R. Blanchette, G. Myers, and T. K. Kirk. 1998. An overview of biomechanical pulping research, p. 309-340. In R. Young, and M. Akhtar (ed.), Environmentally friendly technologies for the pulp and paper industry. John Wiley & Sons, Inc., New York, N.Y. |
| 3. | Bogan, B., B. Schoenike, R. Lamar, and D. Cullen. 1996. Expression of lip genes during growth in soil and oxidation of anthracene by Phanerochaete chrysosporium. Appl. Environ. Microbiol. 62:3697-3703[Abstract]. |
| 4. | Bogan, B., B. Schoenike, R. Lamar, and D. Cullen. 1996. Expression of mnp genes during bioremediation of polycyclic aromatic hydrocarbon-contaminated soil with Phanerochaete chrysosporium. Appl. Environ. Microbiol. 62:2381-2386[Abstract]. |
| 5. |
Boominathan, K.,
T. M. D'Souza,
P. S. Naidu,
C. Dosoretz, and C. A. Reddy.
1993.
Temporal expression of the major lignin peroxidase genes of Phanerochaete chrysosporium.
Appl. Environ. Microbiol.
59:3946-3950 |
| 6. | Broda, P., P. Birch, P. Brooks, and P. Sims. 1996. Lignocellulose degradation by Phanerochaete chrysosporium: gene families and gene expression for a complex process. Mol. Microbiol. 19:923-932[Medline]. |
| 7. |
Brown, J.,
M. Alic, and M. Gold.
1991.
Manganese peroxidase gene transcription in Phanerochaete chrysosporium: activation by manganese.
J. Bacteriol.
173:4101-4106 |
| 8. |
Brown, J.,
D. Li,
M. Alic, and M. Gold.
1993.
Heat shock induction of manganese peroxidase gene transcription in Phanerochaete chrysosporium.
Appl. Environ. Microbiol.
59:4295-4299 |
| 9. |
Brown, J. A.,
J. K. Glenn, and M. H. Gold.
1990.
Manganese regulates expression of manganese peroxidase by Phanerochaete chrysosporium.
J. Bacteriol.
172:3125-3130 |
| 10. |
Chandler, D.,
C. A. Wagnon, and H. Bolton.
1998.
Reverse transcriptase (RT) inhibition of PCR at low concentrations of template and its implications for quantitative RT-PCR.
Appl. Environ. Microbiol.
64:669-677 |
| 11. | Cullen, D. 1997. Recent advances on the molecular genetics of ligninolytic fungi. J. Biotechnol. 53:273-289[Medline]. |
| 12. | Gaskell, J., P. Stewart, P. Kersten, S. Covert, J. Reiser, and D. Cullen. 1994. Establishment of genetic linkage by allele-specific polymerase chain reaction: application to the lignin peroxidase gene family of Phanerochaete chrysosporium. Bio/Technology 12:1372-1375[Medline]. |
| 13. |
Gaskell, J.,
A. Vanden Wymelenberg, and D. Cullen.
1995.
Structure, inheritance, and transcriptional effects of pce1, an insertional element within Phanerochaete chrysosporium lignin peroxidase gene lipI.
Proc. Natl. Acad. Sci. USA
92:7465-7469 |
| 14. | Gettemy, J. M., D. Li, M. Alic, and M. H. Gold. 1997. Truncated-gene reporter system for studying the regulation of manganese peroxidase expression. Curr. Genet. 31:519-524[Medline]. |
| 15. |
Gettemy, J. M.,
B. Ma,
M. Alic, and M. H. Gold.
1998.
Reverse transcription-PCR analysis of the regulation of the manganese peroxidase gene family.
Appl. Environ. Microbiol.
64:569-574 |
| 16. | Gilliland, G., S. Perrin, and H. Bunn. 1990. Competitive PCR for quantitation of mRNA, p. 60-69. In M. Innis, D. Gelfand, J. Sninsky, and T. White (ed.), PCR protocols. Academic Press, Inc., New York, N.Y. |
| 17. |
Gold, M., and M. Alic.
1993.
Molecular biology of the lignin-degrading basidiomycete Phanerochaete chrysosporium.
Microbiol. Rev.
57:605-622 |
| 18. | Holzbaur, E., and M. Tien. 1988. Structure and regulation of a lignin peroxidase gene from Phanerochaete chrysosporium. Biochem. Biophys. Res. Commun. 155:626-633[Medline]. |
| 19. | James, C. M., M. S. S. Felipe, P. F. G. Sims, and P. Broda. 1992. Expression of a single lignin peroxidase-encoding gene in Phanerochaete chrysosporium strain ME446. Gene 114:217-222[Medline]. |
| 20. |
Kersten, P., and D. Cullen.
1993.
Cloning and characterization of a cDNA encoding glyoxal oxidase, a peroxide-producing enzyme from the lignin-degrading basidiomycete Phanerochaete chrysosporium.
Proc. Natl. Acad. Sci. USA
90:7411-7413 |
| 21. |
Kersten, P. J.
1990.
Glyoxal oxidase of Phanerochaete chrysosporium; its characterization and activation by lignin peroxidase.
Proc. Natl. Acad. Sci. USA
87:2936-2940 |
| 22. |
Kersten, P. J., and T. K. Kirk.
1987.
Involvement of a new enzyme, glyoxal oxidase, in extracellular H2O2 production by Phanerochaete chrysosporium.
J. Bacteriol.
169:2195-2201 |
| 23. |
Kersten, P. J.,
C. Witek,
A. Vanden Wymelenberg, and D. Cullen.
1995.
Phanerochaete chrysosporium glyoxal oxidase is encoded by two allelic variants: structure, genomic organization, and heterologous expression of glx1 and glx2.
J. Bacteriol.
177:6106-6110 |
| 24. | Kirk, T. K., and D. Cullen. 1998. Enzymology and molecular genetics of wood degradation by white-rot fungi, p. 273-308. In R. A. Young, and M. Akhtar (ed.), Environmentally friendly technologies for the pulp and paper industry. John Wiley & Sons, Inc., New York, N.Y. |
| 25. | Li, D., M. Alic, J. Brown, and M. H. Gold. 1995. Regulation of manganese peroxidase gene transcription by hydrogen peroxide, chemical stress, and molecular oxygen. Appl. Environ. Microbiol. 61:341-345[Abstract]. |
| 26. |
Li, D.,
M. Alic, and M. Gold.
1994.
Nitrogen regulation of lignin peroxidase gene transcription.
Appl. Environ. Microbiol.
60:3447-3449 |
| 27. |
Moukha, S.,
H. Wosten,
E. Mylius,
M. Asther, and J. Wessels.
1993.
Spatial and temporal accumulation of mRNAs encoding two common lignin peroxidases in Phanerochaete chrysosporium.
J. Bacteriol.
175:3672-3678 |
| 28. | Orth, A., M. Rzhetskaya, D. Cullen, and M. Tien. 1994. Characterization of a cDNA encoding a manganese peroxidase from Phanerochaete chrysosporium: genomic organization of lignin and manganese peroxidase genes. Gene 148:161-165[Medline]. |
| 29. |
Pease, E., and M. Tien.
1992.
Heterogeneity and regulation of manganese peroxidases from Phanerochaete chrysosporium.
J. Bacteriol.
174:3532-3540 |
| 30. |
Reiser, J.,
I. Walther,
C. Fraefel, and A. Fiechter.
1993.
Methods to investigate the expression of lignin peroxidase genes by the white-rot fungus Phanerochaete chrysosporium.
Appl. Environ. Microbiol.
59:2897-2903 |
| 31. |
Stewart, P.,
P. Kersten,
A. Vanden Wymelenberg,
J. Gaskell, and D. Cullen.
1992.
The lignin peroxidase gene family of Phanerochaete chrysosporium: complex regulation by carbon and nitrogen limitation and the identification of a second dimorphic chromosome.
J. Bacteriol.
174:5036-5042 |
| 32. |
Vallim, M. A.,
B. J. H. Janse,
J. Gaskell,
A. Pizzirani-Kleiner, and D. Cullen.
1998.
Phanerochaete chrysosporium cellobiohydrolase and cellobiose dehydrogenase transcripts in wood.
Appl. Environ. Microbiol.
64:1924-1928 |
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