Contents - Faperta

484 Biotechnological Approaches for Pest Management and Ecological Sustainability
and microbial defense and detoxifi cation genes were also induced. An advantage of
this approach is that sequencing is limited to cDNAs representing responsive genes
while the disadvantage is that it is limited to responsive genes, since these are most likely
to be retained during prescreening, and several physiologically important genes may
be missed.
Application of Molecular Markers to Understand Functional
Genomics of Insects
Functional genomics can play an important role in understanding the chemical ecology
of insects (Tittiger, 2004). The ESTs have been used to identify pheromone biosynthetic
genes in B. mori. A database of ESTs from pheromone glands has been used to catalogue
transcription of B. mori (Mita et al., 2003). The -9 desaturase has been confi rmed to be
specifi c to pheromone glands (Yoshiga et al., 2000). The EST databases have also been
used to isolate pheromone fatty acyl-denaturases from D. melanogaster ( Jallon and
Wicker-Thomas, 2003). In Ips pini (Say), HMGGA reductase gene (HMG-R) expression
and enzyme activity levels are simulated by JH III (Tillman et al., 2004). HMG-R plays an
important role in regulation of the mevalonate pathway (Goldstein and Brown, 1990).
Though not directly related to pheromone synthesis, these genes could be the targets
to develop future control strategies to disrupt pheromone synthesis (through RNAi or
specifi c inhibitors).
Feeding coordinately stimulates the mevalonate pathway in male I. pini (Keeling,
Blomquist, and Tittiger, 2004), but is not expected in female I. pini, as they do not produce
ipsdienol (Seybold et al., 1995). However, early steps showing isomerization of isoprenyl
phosphate to dimethylallyl phosphate has been observed in the females, while the later
steps were not. Basal transcript levels for all mevalonate pathway genes, and GPPS in particular,
were signifi cantly higher in males compared to females. Some genes are strongly
induced by feeding, while others are already highly expressed, probably in response to
developmental or environmental cues (Keeling, Blomquist, and Tittiger, 2004). Most
mevalonate pathway genes are coordinately upregulated by JH III in the males.
The molecular basis of perception of pheromones and other odors includes binding
proteins, receptors, degrading enzymes, and the signal transduction pathway (Jacquin-
Joly and Merlin, 2004). The cDNAs synthesized from male antennal RNA have revealed
the presence of four new odor-binding proteins in tobacco hornworm, M. sexta (Robertson
et al., 1999). Microarrays have been used to study pheromone reception in honeybee,
A. mellifera (Grozinger et al., 2003; Whitfi eld, Cziko, and Robinson, 2003). Genes with the
strongest change in expression levels were not as consistently regulated to the less strongly
responding genes (Whitfi eld, Cziko, and Robinson, 2003). Queen mandibular pheromone
(QMP) is a multicomponent pheromone that regulates worker development and behavior
in A. mellifera (Plettner et al., 1996). Microarray analysis has shown that 1,200 genes were
upregulated, and nearly 1,300 were downregulated in QMP exposed workers (Grozinger
et al., 2003). Transcription factors were more highly upregulated than the other functional
groups such as phosphatases, kinases, receptors, etc., suggesting that pheromones can
trigger developmental programs by activating one or more transcription factors, which in
turn regulate the downstream genes.