Abstract
Ophraella communa LeSage is an effective biological control agent of common ragweed, Ambrosia artemisiifolia L., which competes with crops and causes allergic rhinitis and asthma. However, thermal stress negatively affects the developmental fitness and body size of this beetle. High temperatures cause a variety of physiological stress responses in insects, which can cause oxidative damage. We investigated the total protein content and activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and peroxidases (PODs) in O. communa adults when its different developmental stages were exposed to high temperatures (40, 42, and 44°C) for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage), and a whole generation to high temperatures (40, 42, and 44°C) for 3 h each day. A control group was reared at 28 ± 2°C. Under short-term daily phasic high-temperature stress, total protein contents were close to the control as a whole; overall, SOD activities increased significantly, CAT activities were closer to or even higher than the control, POD activities increased at 40°C, decreased at 42 or 44°C; stage-specific response was also observed. Under long-term daily phasic high-temperature stress, total protein content increased significantly at 44°C, SOD activities increased at higher temperatures, decreased at 44°C; CAT activities of females increased at ≤42°C, and decreased at 44°C, CAT activities of males decreased significantly; POD activities of females increased at 40°C, decreased at ≥42°C, POD activities of males decreased at 44°C; and antioxidant enzymes activities in females were significantly higher than those in males. Antioxidative enzymes protect O. communa from oxidative damage caused by thermal stress.
Highlights
Temperature is one of the most important environmental factors affecting life history, behavioral and physiological traits, population structure, and community composition in insects (Zhang et al, 2015b; Esperk et al, 2016)
Total protein contents in O. communa females were significantly affected by the previous exposure of larvae (F3,8 = 52.31, P < 0.0001), pupae (F3,8 = 85.78, P < 0.0001), and adults (F3,8 = 434.51, P = 0.0007) to phasic high temperatures, except for eggs (F3,8 = 3.83, P = 0.0571); the total protein contents were stage-specific when different developmental stages were exposed to any phasic high temperature compared to the control (Table 1)
Total protein contents in O. communa males were significantly affected by the previous exposure of eggs (F3,8 = 53.87, P < 0.0001), larvae (F3,8 = 48.83, P < 0.0001), pupae (F3,8 = 5.85, P = 0.0205), and adults (F3,8 = 32.49, P = 0.0001) to phasic high temperatures; the total protein contents were stage-specific when different developmental stages were exposed to 40 or 42◦C for 3 h compared to the control and 44◦C (Table 2)
Summary
Temperature is one of the most important environmental factors affecting life history, behavioral and physiological traits, population structure, and community composition in insects (Zhang et al, 2015b; Esperk et al, 2016). To prevent damage from ROS, insects have developed antioxidant defense mechanisms and these systems have both enzymatic and non-enzymatic components (Felton and Summers, 1995); antioxidant enzymes are key components in the regulation of intracellular ROS balance (Wang et al, 2012; Jia et al, 2014; Li et al, 2017). Major antioxidative enzymes in insects include superoxide dismutase (SOD), catalase (CAT), and peroxidases (POD) which are reported to be involved in insect defense systems (Zhang et al, 2015a; Li et al, 2017). SOD converts superoxide anion (O2−) into oxygen (O2) and hydrogen peroxide (H2O2), and CAT and POD break down hydrogen peroxide (H2O2) into oxygen and water (Covarrubias et al, 2008; Li et al, 2017), which protect insects from oxidative damage
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