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Molecular Entomology 2013, Vol.4, No.3, 13-21
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17
the two bands increased (Figure 8). The same pattern of
the protease inhibition observed when triticale seed
extract was used (Figure 9). Triticale seed extract
affected the insect protease activity in a dose-dependent
manner, as with wheat seed extract. So, at the highest
dose used the P2 band was completely disappeared and
trace amount of the P1 band left. The effect of the
wheat seed extract on the insect gut protease was more
than triticale seed extract since the high dose (1.7 mg
protein/mL) of the wheat and triticale seed extracts
inhibited the protease activity more than 70% and less
than 60%, respectively.
Figure 8 The effect of the triticale seed extracts on the protease
activity of the carob moth gut
Note: a: control without triticale seed extract; b: 1.7 mg
protein/mL, c: 0.85 mg protein/mL; d: 0.425 mg protein/mL; e:
0.212 mg protein/mL; f: 0.106 mg protein/mL
Figure 9 The effect of the wheat seed extracts on the protease
activity of the carob moth gut
Note: a: control without triticale seed extract; b: 1.7 mg
protein/mL; c: 0.85 mg protein/mL; d: 0.425 mg protein/mL; e:
0.212 mg protein/mL; f: 0.106 mg protein/mL
3 Discussion
In this study it was found that there are two α-amylase
(A1 and A2) isoenzymes and two protease found in
the carob moth digestive system. Presence of different
isoenzymes in insects shows its importance in insect
digestion of carbohydrate to guarantee effective
digestion (Mehrabadi et al., 2012). There are many
reports that some species have more than one
isoenzyme in their digestive system showing their
important role in insect metabolism (Mehrabadi et al.,
2010). Also, the presence of a number of α-amylases
isoenzymes is a strategy to escape plant secondary
metabolites (Silva et al., 1999). Production of more
than one α-amylase also was detected in the other insect
species including
Sitophilus zeamais
,
Callosobruchus
maculatus
,
Zabrotes subfasciatus
,
Acanthoscelides
obtectus
, and
Eurygaster integriceps
(Silva et al., 1999;
Franco et al., 2005; Bandani et al., 2009).
Some insects such as carob moth are somehow
dependent on α-amylases for their survival so these
enzymes could be a good target for insect control
through digestive enzyme inhibitors (Franco et al.,
2002; Svensson et al., 2003; Sivakumar et al., 2006).
Moreover, there are many repots that these plant
defense molecules are abundant in cereals and
legumes, which play an important role in plant
defenses against pests and pathogens (Franco et al.,
2002; Sivakumar et al., 2006). So, in this study the
effect of two cereal species, triticale and wheat, seeds
extracts were tested against carob moth digestive
α-amylase and proteases enzymes. It was found that
wheat seed extract had more inhibitory effect on the
carob moth enzymes (α-amylases and proteases) than
triticale seed extract. However, the effect of the both
wheat and triticale seed extract on α-amylases were
more than proteases. Also, wheat seed extract had
more inhibitory effect on α-amylases than triticale
seed extract i.e. wheat seed extract inhibited the insect
alpha amylase 82% and triticale seed extract inhibited
the insect alpha amylase 75%. Mehrabadi et al. (2010)
showed that triticale seed extract inhibited the Sunn
pest (
Eurygaster integriceps
) α-amylase activity about
80%. Also, in this study it was found that wheat and
triticale seed extracts inhibited general protease
activity of the carob moth 62% and 57%, respectively.
So, interestingly, in this study it was found that wheat
seed extract have more inhibitory activity on both
alpha amylase and protease of the carob moth than