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Survival of silk worm, Bombyx mori in azaserine induced oxidative stress
Venkatesh Mandyam D1, Subramanyam Muthangi1
1Department of Life Science, Bangalore University Bangalore, 560056, India.
Abstract:
Cells under stress generate reactive oxygen species (ROS) in excess, which causes mitochondrial dysfunction and stimulates the apoptotic cascade. However, mild stress or pre-conditioning lead to the evasion of apoptosis by activating mitogenic signaling, including the signaling of inhibitors of apoptosis proteins (IAPs), or by inactivating certain apoptotic molecules. The silkworm (Bombyx mori) is an important economic insect which serves as a model organism in biological research. Bombyx mori apoptotic protease inducing factor (BmApaf1), a death-related ced-3/Nedd2-like protein (BmDredd), and BmSurvivin-2 (BmSvv2) are known to play significant roles in metamorphosis. Azaserine is an analogue of glutamine and irreversibly inhibits glutamine-utilizing enzymes and cysteine-glutamate transporter genes EAAT2. In the present study, we experimentally demonstrated stress induced by azaserine along with the capacity of antioxidants to modulate apoptotic/anti-apoptotic gene expression in determining the fate of the larvae. We observed higher larval survival with higher azaserine dosages and attributed this to the quantum of ROS generated and AOEs response, which favoured the BmSvv2 expression. Meanwhile higher levels of ROS with concomitant changes in AOEs were found to be responsible for BmApaf1 and BmDredd expression, which reflected a higher mortality rate.
Insights
Mild stress can protect cells by activating survival pathways. In silkworms, antioxidants modulated apoptotic gene expression, with higher survival linked to increased BmSurvivin-2 expression under azaserine-induced stress.
Area of Science:
- Cellular stress response
- Apoptosis regulation
- Insect molecular biology
Background:
- Excessive reactive oxygen species (ROS) trigger apoptosis, but mild stress can induce protective mechanisms.
- Inhibitors of apoptosis proteins (IAPs) and mitogenic signaling pathways mediate apoptosis evasion.
- Silkworm (Bombyx mori) genes BmApaf1, BmDredd, and BmSurvivin-2 are crucial for metamorphosis.
Purpose of the Study:
- To investigate the effects of azaserine-induced stress on apoptotic and anti-apoptotic gene expression in silkworm larvae.
- To determine the role of antioxidants in modulating stress response and larval survival.
- To elucidate the relationship between ROS levels, antioxidant response, and the expression of key apoptotic/anti-apoptotic genes.
Main Methods:
- Induction of stress in silkworm larvae using varying dosages of azaserine.
- Measurement of reactive oxygen species (ROS) levels.
- Quantification of antioxidant enzyme (AOE) activity.
- Analysis of gene expression for BmApaf1, BmDredd, and BmSurvivin-2.
Main Results:
- Higher azaserine dosages correlated with increased larval survival, attributed to ROS levels and antioxidant response favoring BmSvv2 expression.
- Elevated ROS levels and altered AOE activity were associated with increased expression of BmApaf1 and BmDredd, leading to higher mortality.
- Antioxidants played a role in modulating the balance between pro-apoptotic and anti-apoptotic gene expression.
Conclusions:
- Azaserine-induced stress in silkworms demonstrates a complex interplay between ROS, antioxidant responses, and apoptosis regulation.
- The expression of BmSvv2 is linked to enhanced larval survival under stress, while BmApaf1 and BmDredd expression correlate with mortality.
- This study highlights the potential of antioxidants in mitigating stress-induced apoptosis in insects.
