Biochemical studies of amylases in the silkworm, Bombyx mori L.: Comparative analysis in diapausing and nondiapausing strains

Abstract

Abstract--Different amylase enzymes were identified by analysis of digestive fluid and haemolymph in diapausing and nondiapausing strains of silkworm, Bombyx mori. The diapausing strain showed negligible digestive amylase activity at a pH range of 3-11, while the nondiapausing strain registered strikingly higher amylase activity at pH 9.2. Higher levels of undigested starch was found in the faecal matter of the diapausing strain, which is consistent with the negligible digestive amylase activity. Developmental specific expression of haemolymph amylase activity was seen in nondiapausing and diapausing strains. In the nondiapausing strain the digestive amylase activity was at its peak during intermoult and depressed during moult. PAGE analysis revealed the occurrence of only anodal digestive and haemolymph amylases in the diapausing strain, whereas both cathodal and anodal enzymes were seen in the digestive fluid and haemolymph of the nondiapausing strain.

Comparative Analysis of Digestive Amylase Activity in some Tropical and Temperate Breeds of Mulberry Silkworm, <i>Bombyx mori</i> L.

“…In a similar kind of study, maximum amylase activity was found in late middle part of the fifth instar of silkworm 16 . Higher digestive amylase activity in low yielding breeds (multivoltines) and low digestive amylase activity in high yielding breeds (bivoltines) exhibited in the present study also receive support from the findings of many other authors who revealed that diapausing strains showed negligible digestive amylase activity, while the non-diapausing strains registered strikingly higher amylase activity 4,14,17 . However variations in the levels of digestive amylase activity could be attributed to the physiological status of the insect that increases its feed consumption and utilization efficiencies.…”

“…Digestive juice samples were centrifuged @ 10,000 r/10 min (ref. 4). The supernatant was transferred to new tubes and kept at -20C for analysis.…”

“…However variations in the levels of digestive amylase activity could be attributed to the physiological status of the insect that increases its feed consumption and utilization efficiencies. Also, it could be due to the reason that digestibility of starch in multivoltine and bivoltine breeds is quite different 4 . In the present study bivoltine breeds performed comparatively better in spring and among them the activity of digestive amylase was much higher in SKUAST-28 than other breeds during both seasons; however in multivoltines, the activity in summer was relatively higher than in spring season.…”

“…There was an increase in digestive amylase activity from the first day to fifth day of the fifth instar and, thereafter, its activity decreased. Several studies on the activity of digestive amylases in silkworm have revealed that activity is strong during the feeding period of the fourth and fifth instar larvae and weak at third ecdysis 4,12 . It was also observed during the present study that the activity of digestive amylase was at its peak level on the fifth day of the fifth instar.…”

“…The ability to digest more food influences the growth, development and resistance to diseases, stresses and better survival under different environmental conditions 3 . Amylases from different origins have been characterized 4,5 . The effect of BmNPV infection on the digestive enzyme activity in the silkworm, Bombyx mori was studied earlier by others and the activities of amylase, invertase, trehalase and protease were analysed in the infected silkworms 6 .…”