Genome, transcriptome, and secretome analysis of wood decay fungus Postia placenta supports unique mechanisms of lignocellulose conversion.
Brown-rot fungi such as Postia placenta are common inhabitants of forest ecosystems and are also largely responsible for the destructive decay of wooden structures. Rapid depolymerization of cellulose is a distinguishing feature of brown-rot, but the biochemical mechanisms and underlying genetics are poorly understood. Systematic examination of the P. placenta genome, transcriptome, and secretome revealed unique extracellular enzyme systems, including an unusual repertoire of extracellular glycoside hydrolases. Genes encoding exocellobiohydrolases and cellulose-binding domains, typical of cellulolytic microbes, are absent in this efficient cellulose-degrading fungus. When P. placenta was grown in medium containing cellulose as sole carbon source, transcripts corresponding to many hemicellulases and to a single putative beta-1-4 endoglucanase were expressed at high levels relative to glucose-grown cultures. These transcript profiles were confirmed by direct identification of peptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Also up-regulated during growth on cellulose medium were putative iron reductases, quinone reductase, and structurally divergent oxidases potentially involved in extracellular generation of Fe(II) and H(2)O(2). These observations are consistent with a biodegradative role for Fenton chemistry in which Fe(II) and H(2)O(2) react to form hydroxyl radicals, highly reactive oxidants capable of depolymerizing cellulose. The P. placenta genome resources provide unparalleled opportunities for investigating such unusual mechanisms of cellulose conversion. More broadly, the genome offers insight into the diversification of lignocellulose degrading mechanisms in fungi. Comparisons with the closely related white-rot fungus Phanerochaete chrysosporium support an evolutionary shift from white-rot to brown-rot during which the capacity for efficient depolymerization of lignin was lost.
Martinez
Diego
D
Los Alamos National Laboratory/Joint Genome Institute, P.O. Box 1663, Los Alamos, NM 87545, USA.
Challacombe
Jean
J
Morgenstern
Ingo
I
Hibbett
David
D
Schmoll
Monika
M
Kubicek
Christian P
CP
Ferreira
Patricia
P
Ruiz-Duenas
Francisco J
FJ
Martinez
Angel T
AT
Kersten
Phil
P
Hammel
Kenneth E
KE
Vanden Wymelenberg
Amber
A
Gaskell
Jill
J
Lindquist
Erika
E
Sabat
Grzegorz
G
Bondurant
Sandra Splinter
SS
Larrondo
Luis F
LF
Canessa
Paulo
P
Vicuna
Rafael
R
Yadav
Jagjit
J
Doddapaneni
Harshavardhan
H
Subramanian
Venkataramanan
V
Pisabarro
Antonio G
AG
Lavín
José L
JL
Oguiza
José A
JA
Master
Emma
E
Henrissat
Bernard
B
Coutinho
Pedro M
PM
Harris
Paul
P
Magnuson
Jon Karl
JK
Baker
Scott E
SE
Bruno
Kenneth
K
Kenealy
William
W
Hoegger
Patrik J
PJ
Kües
Ursula
U
Ramaiya
Preethi
P
Lucas
Susan
S
Salamov
Asaf
A
Shapiro
Harris
H
Tu
Hank
H
Chee
Christine L
CL
Misra
Monica
M
Xie
Gary
G
Teter
Sarah
S
Yaver
Debbie
D
James
Tim
T
Mokrejs
Martin
M
Pospisek
Martin
M
Grigoriev
Igor V
IV
Brettin
Thomas
T
Rokhsar
Dan
D
Berka
Randy
R
Cullen
Dan
D
D001483:Base Sequence; D005075:Biological Evolution; D044602:Cellulases; D004798:Enzymes / Q000235:genetics; D020869:Gene Expression Profiling; D016681:Genome, Fungal; D006026:Glycoside Hydrolases; D008031:Lignin / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008969:Molecular Sequence Data; D010088:Oxidoreductases; D020072:Polyporales / Q000235:genetics* / Q000378:metabolism; D014934:Wood / Q000378:metabolism
D004798:Enzymes; C036909:lignocellulose; D008031:Lignin; D010088:Oxidoreductases; D044602:Cellulases; D006026:Glycoside Hydrolases