Basic HTML Version
Genomics and Applied Biology
, 2012, Vol.3 No.2 8-21
http://gab.sophiapublisher.com
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Figure 1 Regulation of proteinase inhibitor gene in plant
Note: Green arrow: activation; red arrow: inhibition; black/blue
arrow: direction of reaction
Figure 2 Larval growth curve of second (A) and third (B)
instar Helicoverpa armigera larvae fed on artificial diet
containing ChTI (5000 TIU/mL) and control on same diet
without ChTI
Note: Each value represents the mean weight of 20 larvae from
five independent replicates ± SE
4 Role of proteinase inhibitors in plants
Plant PIs are known to play important role in plant’s
defense against insect-pest and pathogens as well as
regulation of endogenous proteinases (Mosolov et al.,
2001; Birk, 2003; Shewry, 2003). They are of interest
in plant biology as source of (1) resistance against
pests and pathogens, (2) drugs with antiviral
properties and (3) markers for studying plant diversity
and evolution (Konarev et al., 2002; Lawrence and
Koundal, 2002; Korsinczky et al., 2004).
4.1 In insect pest control
Serine proteinases have been identified in gut extracts
of many lepidopteran insects (Houseman et al., 1989)
and many of these enzymes are inhibited by proteinase
inhibitors. The pH of lepidopteran guts are alkaline,
ranging from 9.0-11.0 (Applebaum, 1985) wherein
serine- and metallo-proteinases are most active. Hence,
serine proteinase inhibitors show anti-nutritional effects
against several lepidopteran insects (Shulke and
Murdock, 1983; Applebaum, 1985). Nandeesha and
Prasad (2001) have reported partially purified subabul
trypsin inhibitor (STI) from
Leucaena leucacephala
with molecular weight of 15 kD that shows high-level
thermo tolerance and pH stability. Bioassay reveals that
STI is a strong inhibitor of
H. armigera
, extending
larval growth period by 12 days and induces mortality
by 40% at 20,000 TIU/mL concentrations.
Dimorphandra mollis
seed trypsin inhibitor (DMTI-
Ⅱ
)
showed
67%
mortality
among
bruchid,
(
Callosobruchus maculates
) fed at 1% level in artificial
diet (Macedo et al., 2002). Giri et al (2003) reported at
least 14 trypsin inhibitors from
Psophocarpus
tetragonolobus
seeds. WBTI-1 (28 kD) was identified
as a potent inhibitor of HGP activity (94%). WBTI-2
(24 kD) and WBTI-4 (20 kD) inhibited HGP activity up
to 85%. WBTI-3-5-7 showed limited inhibition of HGP
as compared with trypsin. Barley (
Hordeum vulgare
L.)
malt contains all the four classes of endoproteinases as
well as low molecular weight peptides that inhibit many
of these endoproteinases. These are chloroform/
methanol soluble peptides, possibly play a significant
role in controlling the activity of barley proteinases
during germination, and protecting seed and young
plant from pathogens/pests (Jones and Fontanini, 2003).
Cotton boll weevil,
Anthonomus grandis
, feeds on
fruits and buds causing severe crop loss. Trypsin/
chymotrypsin inhibitor (BTCI) purified from Vigna
unguiculata seeds showed low inhibitory activity
against trypsin-like proteinases of adult weevils. The
bioassay results strongly suggest that BTCI has
potential to engineer crop plants for resistance to the
cotton boll weevil (Franco et al., 2003). Peltophorum
dubium seed trypsin inhibitor (20 kD), thermo stable
kunitz type inhibitor showed 56% mortality in
Anagasta kuehniella at 1.6% level (Rodrigues et al.,
2003). Chougule et al (2003) analyzed seeds of 53