Abstract
The phlebotomine sand fly Lutzomyia longipalpis is the most important vector of American visceral leishmaniasis (AVL), the disseminated and most serious form of the disease in Central and South America. In the natural environment, most female L. longipalpis are thought to survive for less than 10 days and will feed on blood only once or twice during their lifetime. Successful transmission of parasites occurs when a Leishmania-infected female sand fly feeds on a new host. Knowledge of factors affecting sand fly longevity that lead to a reduction in lifespan could result in a decrease in parasite transmission. Catalase has been found to play a major role in survival and fecundity in many insect species. It is a strong antioxidant enzyme that breaks down toxic reactive oxygen species (ROS). Ovarian catalase was found to accumulate in the developing sand fly oocyte from 12 to 48 hours after blood feeding. Catalase expression in ovaries as well as oocyte numbers was found to decrease with age. This reduction was not found in flies when fed on the antioxidant ascorbic acid in the sugar meal, a condition that increased mortality and activation of the prophenoloxidase cascade. RNA interference was used to silence catalase gene expression in female Lu. longipalpis. Depletion of catalase led to a significant increase of mortality and a reduction in the number of developing oocytes produced after blood feeding. These results demonstrate the central role that catalase and ROS play in the longevity and fecundity of phlebotomine sand flies.
Highlights
The phlebotomine sand fly Lutzomyia longipalpis, Lutz and Neiva 1912 is the best studied and most important vector of American Visceral Leishmaniasis (AVL) [1,2]
Biological damage related to reactive oxygen species (ROS) production has been implicated in the process of ageing in dipterans like Drosophila melanogaster, previous work done on this species showed that oxidative stress increases with age, while antioxidant enzyme activity decreased over time [13,14,15]
The present study suggests for the first time that catalasemediated ROS scavenging has a significant impact on female Lu. longipalpis fecundity and survival
Summary
The phlebotomine sand fly Lutzomyia longipalpis, Lutz and Neiva 1912 is the best studied and most important vector of American Visceral Leishmaniasis (AVL) [1,2]. Female Lu. longipalpis from the older age group showed a decrease in the number of developing oocytes dissected five days after blood feeding in comparison to younger sand flies(fig. To confirm the role of endogenous ROS-scavenging in fecundity catalase was depleted using RNAi. Flies injected with 144 ng of dsRNA for catalase (dsCAT) showed a dramatic decrease in oocyte number dissected 48 hours after blood feeding 5C), with no effects on the catalase expression in the midgut (data not shown) These results confirm that endogenous ROS-scavenging in developing oocytes plays a major role in female Lu. longipalpis fecundity. 7), compared to flies injected with a non-related dsRNA (dsGFP) and non-injected flies These results show that ROS-scavenging by either endogenous or exogenous antioxidants play an important role in female Lu. longipalpis survival
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