Plant Molecular Biology 41: 313–319, 1999.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
Coexpression of a defensin gene and a thionin-like gene via different signal
transduction pathways in pepper and Colletotrichum gloeosporioides
, Moon Kyung Ko, Igor Kostenyuk, Byongchul Shin and Kwang Sang Kim
Kumho Life and EnvironmentalScienceLaboratory, Korea Kumho Petrochemical Co., Ltd, 1 Oryong-dong, Puk-gu,
Kwangju 500-712, Korea (
author for correspondence)
Received 20 January 1999; accepted in revised form 9 August 1999
Key words: Colletotrichum gloeosporioides, defensin, fruit ripening, incompatible interaction, pepper, thionin
The anthracnose fungus, Colletotrichum gloeosporioides, interacts incompatibly with the ripe fruit of pepper
(Capsicum annuum). It interacts compatibly with the unripe-mature fruit. We isolated a defensin gene, j1-1,anda
thionin-like gene, PepThi, expressed in the incompatible interactionby using an mRNA differential display method.
Both genes were developmentally regulated during fruit ripening, organ-speciﬁcally regulated, and differentially
induced during the compatible and incompatible interactions. Expression of the PepThi gene was rapidly induced
in the incompatible-ripe fruit upon fungal infection. The fungus-inducible PepThi gene is highly inducible only in
the unripe fruit by salicylic acid. In both ripe and unripe fruit, it was induced by wounding, but not by jasmonic
acid. Expression of the j1-1 gene is enhanced by jasmonic acid in the unripe fruit but suppressed in the ripe fruit.
These results suggest that both small and cysteine-rich protein genes are induced via different signal transduction
pathways during fruit ripening to protect the reproductive organs against biotic and abiotic stresses.
Plants have developed defense mechanisms to defend
themselves against phytopathogens. Plants’ ﬁrst re-
sponses to pathogen infection include fortiﬁcation of
the cell wall for physical barriers by the deposition
of lignin (Dean and Kúc, 1988) and by oxidative
cross-linking (Brisson et al., 1994) as well as the
hypersensitive reaction (HR). HR causes a rapid cell
death of infected tissues to halt further colonization
by the pathogen (Goodman and Novacky, 1994). The
next array of defense strategies includes the produc-
tion of antimicrobial phytoalexins (van Etten et al.,
1989), pathogenesis-related (PR) proteins (Linthorst,
1991; Ponstein et al., 1994), and cysteine (Cys)-rich
proteins, such as lipid transfer protein (Garcia-Olmedo
et al., 1995) and thionins (Bohlmann, 1994).
The nucleotide sequence data reported will appear in the EMBL
and GenBank Nucleotide Sequence Databases under the accession
number AF112443 (PepThi).
Thionins are small, highly basic, Cys-rich pro-
teins that show antimicrobial activity and seem to
have a role in plant defense against fungi and bac-
teria. The overexpression of the THI2.1 thionin in
Arabidopsis enhanced resistance to a phytopathogenic
fungus (Epple et al., 1997). The overexpression of α-
hordothionin in tobacco also enhanced resistance to a
phytopathogenic bacterium (Carmona et al., 1993). In
addition, during barley and powdery mildew interac-
tions, the accumulation of thionins was higher in the
incompatible interaction than in the compatible one
(Ebrahim-Nesbat et al., 1993).
The thionins contain a signal sequence, the thionin
domain and an acid polypeptide domain as well as
the conserved Cys residues (Bohlmann et al., 1994).
A new class of Cys-rich antimicrobial protein, γ -
thionin, has a similar size (5 kDa) and the same
number of disulﬁde bridges as thionins. However,
since γ -thionins do not have signiﬁcant sequence ho-
mologies with thionins, they have been described as