Detoxification of Gramine by the Cereal Aphid
Sitobion avenae
Qing-Nian Cai
&
Ying Han
&
Ya-Zhong Cao
&
Yuan Hu
&
Xin Zhao
&
Jian-Long Bi
Received: 26 October 2008 /Revised: 13 January 2009 /Accepted: 21 January 2009 /Published online: 18 February 2009
#
The Author(s) 2009. This article is published with open access at Springerlink.com
Abstract Secondary metabolites play an important role in
host plant resistance to insects, and insects, in turn, may
develop mechanisms to counter plant resistance mecha-
nisms. In this study, we investigated the toxicity of gramine
to the cereal aphid Sitobion avenae and some enzymatic
responses of S. avenae to this alkaloid. When S. avenae fed
on an artificial diet containing gramine, mortality occurred
in a dose-dependent manner. The LC
50
of gramine was
determined to be 1.248 mM. In response to gramine, S.
avenae developed increased activities of carboxylesterase
and glutathione S-transferase, two important detoxification
enzymes. The activities of both enzymes were positively
correlated with the concentration of dietary gramine. In
addition, the activities of peroxidase and polypheolic oxidase,
two important oxidoreductase enzymes in S. avenae,in-
creased in response to gramine; however, catalase activity
decreased when insects were exposed to higher levels of
dietary gramine. The potential role of gramine in host plant
resistance and S. avenae counter-resistance is discussed.
Keywords Gramine
.
Sitobion avenae
.
Carboxylesterase
.
Glutathione S-transferase
.
Peroxidase
.
Polyphenol oxidase
.
Catalase
Introduction
Host plant resistance against insects is recognized as an
important component of integrated insect pest management
(Gao 1994; Schotzko and Bosque-pérez 2000; Li et al.
2001). Plant resistance is attributed largely to secondary
metabolites such as phenolics, nonprotein amino acids, and
alkaloids, which are documented to be deleterious to insect
herbivores (Manuwoto and Scriber 1985; Ciepiela and
Sempruch 1999; Wang et al. 2006).
Many alkaloids are strong deterrents to aphids and other
herbivores and have been used as botanical insecticides
and/or antixenotic chemicals (Luo et al. 1997; Jiang et al.
1999). Gramine, a simple indole alkaloid found in barley
and other crop plants, occurs widely in plants of Gramineae
and has a wide range of biological activities against insects,
mammals, and bacteria (Corcuera 1984, 1993; Züñiga and
Corcuera 1986; Leszczynski et al. 1989).
In the plant–insect ecosystem, insect detoxification
enzymes (i.e., esterase and glutathione S-transferase) and
oxidoreductases (i.e., polyphenol oxidase, peroxidase, and
catalase) are important antiresistant agents against the
secondary metabolites found in their host plants. Their role
in overcoming plant resistance has been studied extensively
in a number of insect species (Gao et al. 1997; Figueroa
et al. 1999; Luo and Zhang 2003). However, little is known
about the changes of detoxification enzymes and oxido-
reductases in aphids in response to gramine.
The present study was conducted to elucidate some of
the biochemical mechanism(s) of gramine in host plant
resistance and to determine how the English grain aphid,
Sitobion avenae (F.), counters this resistance. The specific
objectives were (1) to assess the direct toxicity of gramine
to S. avenae and (2) to determine activities of detoxification
enzymes and oxidoreductases in S. avenae in response to
gramine in its diet.
J Chem Ecol (2009) 35:320–325
DOI 10.1007/s10886-009-9603-y
Q.-N. Cai
:
Y. Han
:
Y. H u
:
X. Zhao
College of Agronomy and Biotechnology,
China Agricultural University,
Beijing 100094, People’s Republic of China
Y.-Z. Cao
Institute of Plant Protection,
Chinese Academy of Agricultural Science,
Beijing 100094, People’s Republic of China
J.-L. Bi (*)
University of California Cooperative Extension,
Salinas, CA 93901, USA
e-mail: jbi@ucdavis.edu