Limits...
Genetic transformation of lignin degrading fungi facilitated by Agrobacterium tumefaciens.

Sharma KK, Kuhad RC - BMC Biotechnol. (2010)

Bottom Line: The fungal transformants were confirmed by PCR and Southern hybridization.The transformation efficiency was maximum at 20°C whereas no transfer was observed at temperature above 29°C.These findings provide a rapid and reproducible transformation method without external addition of acetosyringone, which could be useful for improving white-rot fungi for their various biotechnological applications.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lignocellulose Biotechnology Laboratory, Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi, India.

ABSTRACT

Background: White-rot fungi are primarily the major degraders of lignin, a major obstacle for commercial exploitation of plant byproducts to produce bioethanol and other industrially important products. However, to improve their efficacy for lignin degradation, it has become necessary to genetically modify these organisms using appropriate vectors. Agrobacterium tumefaciens, a soil phytopathogenic bacterium, generally transforms plants by delivering a portion of the resident Ti- plasmid, the T-DNA (transfer DNA). The trans-Kingdom gene transfer is initiated by the activity of Ti-plasmid encoded vir (virulence) genes in response to low-molecular-mass phenolic compounds such as acetosyringone. A. tumefaciens played a major role in plant genetic engineering and basic research in molecular biology, accounting for nearly 80% of the transgenic plants produced so far. Initially, it was believed that only dicotyledons, gymnosperms and a few monocotyledonous species could be transformed by this bacterium; but recent reports have totally changed this scenario by demonstrating that many 'recalcitrant' species not included in its natural host range can also be transformed, especially filamentous fungi.

Results: This paper describes an efficient and convenient Agrobacterium-mediated gene transformation system for successful delivery of T-DNA, carrying the genes coding for β-glucuronidase (uidA), green fluorescent protein (gfp) and hygromycin phosphotransferase (hpt) to the nuclear genome of lignin degrading white-rot fungi such as Phanerochaete chrysosporium, Ganoderma sp. RCKK-02, Pycnoporous cinnabarinus, Crinipellis sp. RCK-1, Pleurotus sajor-caju and fungal isolate BHR-UDSC without supplementation of acetosyringone. The fungal transformants were confirmed by PCR and Southern hybridization. The expression vector pCAMBIA 1304-RCKK was constructed by the addition of GPD promoter from plasmid p416 to the binary vector backbone pCAMBIA1304, which controls uidA and gfp gene. Transmission Electron Microscope (TEM) analysis revealed the attachment of bacterial cells to the fungal hyphae. Transformation frequency varied from 50 to 75% depending on the fungal species used in this study. The transformation efficiency was maximum at 20°C whereas no transfer was observed at temperature above 29°C.

Conclusion: These findings provide a rapid and reproducible transformation method without external addition of acetosyringone, which could be useful for improving white-rot fungi for their various biotechnological applications.

Show MeSH

Related in: MedlinePlus

HPLC profiles of phenolic extracts from lignin (commercial) (E) and wheat bran (F). The peak at retention time (RT) 23.19 was identified as acetosyringone. Different compounds of lignin monomer pathways were used as standards, i.e. acetosyringone, RT 23.19 (A); caffeic acid, RT12.142 (B); 4-hydroxybenzylalcohol RT 37.642 (C) and cinnamic acid RT 26.350 (D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2944332&req=5

Figure 4: HPLC profiles of phenolic extracts from lignin (commercial) (E) and wheat bran (F). The peak at retention time (RT) 23.19 was identified as acetosyringone. Different compounds of lignin monomer pathways were used as standards, i.e. acetosyringone, RT 23.19 (A); caffeic acid, RT12.142 (B); 4-hydroxybenzylalcohol RT 37.642 (C) and cinnamic acid RT 26.350 (D).

Mentions: The HPLC profile of the degraded lignin compound confirmed the presence of different intermediates of lignin synthesis pathway. The presence of acetosyringone in fungus-degraded lignin supernatant advocates the transformation of fungal mycelia grown in lignin-supplemented media. In addition to well established vir-gene inducer, i.e. acetosyringone, we also detected some additional phenolic compounds like caffeic acid, 4-hydroxybenzyl alcohol and cinnamic acid (Figure 4). HPLC profile also showed few unidentified peaks, which made us to hypothesize that there might be some synergistic or cumulative effect of different phenolic compounds, resulting in high transformation efficiency.


Genetic transformation of lignin degrading fungi facilitated by Agrobacterium tumefaciens.

Sharma KK, Kuhad RC - BMC Biotechnol. (2010)

HPLC profiles of phenolic extracts from lignin (commercial) (E) and wheat bran (F). The peak at retention time (RT) 23.19 was identified as acetosyringone. Different compounds of lignin monomer pathways were used as standards, i.e. acetosyringone, RT 23.19 (A); caffeic acid, RT12.142 (B); 4-hydroxybenzylalcohol RT 37.642 (C) and cinnamic acid RT 26.350 (D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2944332&req=5

Figure 4: HPLC profiles of phenolic extracts from lignin (commercial) (E) and wheat bran (F). The peak at retention time (RT) 23.19 was identified as acetosyringone. Different compounds of lignin monomer pathways were used as standards, i.e. acetosyringone, RT 23.19 (A); caffeic acid, RT12.142 (B); 4-hydroxybenzylalcohol RT 37.642 (C) and cinnamic acid RT 26.350 (D).
Mentions: The HPLC profile of the degraded lignin compound confirmed the presence of different intermediates of lignin synthesis pathway. The presence of acetosyringone in fungus-degraded lignin supernatant advocates the transformation of fungal mycelia grown in lignin-supplemented media. In addition to well established vir-gene inducer, i.e. acetosyringone, we also detected some additional phenolic compounds like caffeic acid, 4-hydroxybenzyl alcohol and cinnamic acid (Figure 4). HPLC profile also showed few unidentified peaks, which made us to hypothesize that there might be some synergistic or cumulative effect of different phenolic compounds, resulting in high transformation efficiency.

Bottom Line: The fungal transformants were confirmed by PCR and Southern hybridization.The transformation efficiency was maximum at 20°C whereas no transfer was observed at temperature above 29°C.These findings provide a rapid and reproducible transformation method without external addition of acetosyringone, which could be useful for improving white-rot fungi for their various biotechnological applications.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lignocellulose Biotechnology Laboratory, Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi, India.

ABSTRACT

Background: White-rot fungi are primarily the major degraders of lignin, a major obstacle for commercial exploitation of plant byproducts to produce bioethanol and other industrially important products. However, to improve their efficacy for lignin degradation, it has become necessary to genetically modify these organisms using appropriate vectors. Agrobacterium tumefaciens, a soil phytopathogenic bacterium, generally transforms plants by delivering a portion of the resident Ti- plasmid, the T-DNA (transfer DNA). The trans-Kingdom gene transfer is initiated by the activity of Ti-plasmid encoded vir (virulence) genes in response to low-molecular-mass phenolic compounds such as acetosyringone. A. tumefaciens played a major role in plant genetic engineering and basic research in molecular biology, accounting for nearly 80% of the transgenic plants produced so far. Initially, it was believed that only dicotyledons, gymnosperms and a few monocotyledonous species could be transformed by this bacterium; but recent reports have totally changed this scenario by demonstrating that many 'recalcitrant' species not included in its natural host range can also be transformed, especially filamentous fungi.

Results: This paper describes an efficient and convenient Agrobacterium-mediated gene transformation system for successful delivery of T-DNA, carrying the genes coding for β-glucuronidase (uidA), green fluorescent protein (gfp) and hygromycin phosphotransferase (hpt) to the nuclear genome of lignin degrading white-rot fungi such as Phanerochaete chrysosporium, Ganoderma sp. RCKK-02, Pycnoporous cinnabarinus, Crinipellis sp. RCK-1, Pleurotus sajor-caju and fungal isolate BHR-UDSC without supplementation of acetosyringone. The fungal transformants were confirmed by PCR and Southern hybridization. The expression vector pCAMBIA 1304-RCKK was constructed by the addition of GPD promoter from plasmid p416 to the binary vector backbone pCAMBIA1304, which controls uidA and gfp gene. Transmission Electron Microscope (TEM) analysis revealed the attachment of bacterial cells to the fungal hyphae. Transformation frequency varied from 50 to 75% depending on the fungal species used in this study. The transformation efficiency was maximum at 20°C whereas no transfer was observed at temperature above 29°C.

Conclusion: These findings provide a rapid and reproducible transformation method without external addition of acetosyringone, which could be useful for improving white-rot fungi for their various biotechnological applications.

Show MeSH
Related in: MedlinePlus