Biotechnology Letters 24: 383–389, 2002.
© 2002 Kluwer Academic Publishers. Printed in the Netherlands.
Enhanced resistance to the poplar fungal pathogen, Septoria musiva,in
hybrid poplar clones transformed with genes encoding antimicrobial
Haiying Liang, Catharine M. Catranis, Charles A. Maynard & William A. Powell
College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA
Author for correspondence (Fax: 315-470-6934; E-mail: email@example.com)
Received 16 November 2001; Revisions requested 14 December 2001; Revisions received 4 January 2002; Accepted 7 January 2002
Key words: antimicrobial peptides, biomass species, pathogen resistance, Septoria leaf spot, transgenic trees
Plasmids, pCA1 and pCWEA1, carrying antimicrobial peptide gene(s), Ac-AMP1.2 and ESF12, were used to
transform hybrid poplar clones Ogy and NM6. Peptide Ac-AMP1.2 is an analog of Ac-AMP1 which is one of
the smallest chitin-binding proteins. Synthetic peptide ESF12 mimics the amphipathic α-helix found in magainins.
Transgene mRNA was detected in the transformed plants. When evaluated for resistance to hybrid poplar pathogen
Septoria musiva with an in vitro leaf disk assay, the transformed Ogy plants showed signiﬁcantly increased
pathogen resistance as compared to the untransformed Ogy.
The hybrid poplar is an important woody biomass and
potential bioenergy tree species. This tree species has
economic value as a good source for fuel, pulpwood,
and solid wood products (Ostry & McNabb 1985).
However, utilization of hybrid poplar is limited in the
eastern United States due to a fungal pathogen, Septo-
ria musiva. This fungus causes necrotic lesions in the
leaves and canker formation on the stems and branches
(Moore & Wilson 1983). Leaf spot can reduce the
photosynthetic area and cause premature defoliation
thereby decreasing annual growth. The cankers on
the main stem can reduce growth, predispose the tree
to colonization by secondary organisms, and cause
severe girdling and breakage of the main stem. In ad-
dition, the wood of surviving trees is unsuitable for
pulp production (Ostry & McNabb 1983). Biomass
losses due to this pathogen vary among clones but
losses as high as 63% in a plantation had been re-
ported (McNabb et al. 1982). Although chemical and
cultural control of Septoria leaf spot and canker has
been tried, it was found to be problematic and only
partially effective (Ostry & McNabb 1983, Yang et al.
Enhancing disease resistance in plants by intro-
duction of small antimicrobial peptide genes has been
tried in some annual crops, like tobacco (Huang et al.
1997, Cary et al. 2000, Li et al. 2001), with mixed
results regarding pathogen resistance. However, there
are no data available on woody plants to date. In this
study, we report for the ﬁrst time on the transformation
of hybrid poplar with antimicrobial peptide genes (Ac-
AMP1.2 and ESF12) and the potential resistance of
the transgenic plants to fungal disease caused by the
hybrid poplar pathogen, S. musiva.
Chitin is an important structural component of the
cell wall of fungi but is not found in higher plants
(Raikhel & Lee 1993). Ac-AMP1 (29 amino acid
residues) (Broekaert et al. 1992) is one of the small-
est chitin-binding proteins and was isolated from the
seed coat of amaranth (Amaranthus caudatus). This
peptide, Ac-AMP1, inhibits the growth of several
different plant-pathogenic fungi at much lower con-
centrations than other known antifungal chitin-binding
proteins. In addition, this peptide does not agglutinate
erythrocytes, indicating low toxicity to mammalian