Abstract
In vertebrates dysregulation of the antioxidant defense system has a detrimental impact on male fertility and reproductive physiology. However, in insects, especially mosquitoes the importance of sperm quality has been poorly studied. Since long-term storage of healthy and viable sperm earmarks male reproductive competency, we tested whether the heme peroxidase, a member of antioxidant enzyme family proteins, and abundantly expressed in the testis, also influence male fertility in the mosquito An. stephensi. Here, we show that a heme peroxidase 12 (HPX12), is an important cellular factor to protect the sperms from oxidative stress, and maintains semen quality in the male mosquito reproductive organ. We demonstrate that knockdown of the HPX12 not only impairs the sperm parameters such as motility, viability but also causes a significant down-regulation of MAG expressing transcripts such as ASTEI02706, ASTEI00744, ASTEI10266, likely encoding putative Accessory gland proteins. Mating with HPX12 knockdown male mosquitoes, resulted in ~ 50% reduction in egg-laying, coupled with diminished larval hatchability of a gravid female mosquito. Our data further outlines that increased ROS in the HPX12 mRNA depleted mosquitoes is the ultimate cause of sperm disabilities both qualitatively as well as quantitatively. Our data provide evidence that testis expressing AsHPX12 is crucial for maintaining optimal homeostasis for storing and protecting healthy sperms in the male mosquito’s reproductive organs. Since, high reproductive capacity directly influences the mosquito population, manipulating male mosquito reproductive physiology could be an attractive tool to combat vector-borne diseases.
Highlights
In vertebrates dysregulation of the antioxidant defense system has a detrimental impact on male fertility and reproductive physiology
A higher expression of antioxidant stress (AOS) related transcripts was observed in newly emerged males than in female mosquitoes (Supplemental Fig. 4a,c), where heme peroxidase 12 (HPX12) expression level was > fourfold (p < 0.00045) higher in the male reproductive organ (MRO) than midgut, salivary glands, and hemocytes (Fig. 1b)
After 24 h of mixing, a significant loss was observed in the expression level of HPX12 (p < 0.0003) (Fig. 1d), allowing us to hypothesize and test its possible role in the male fertility
Summary
In vertebrates dysregulation of the antioxidant defense system has a detrimental impact on male fertility and reproductive physiology. Male mosquitoesgain sexual maturity in order to be competent for copulation while s warming[8,9,10] In nature, it is the morphological features such as body size, age and diet which serve as an important indicator for male fitness, and other factors such as temperature, swarm size and time of swarming have an impact on the reproductive physiology, sperm quality, and seminal fluid d iversity[11,12,13,14]. Insects/mosquitoes have convincingly evidenced that Male accessory gland (MAG) originating seminal fluid, influences the reproductive physiology of the mated female right from sperm deposition in the reproductive tract to egg laying[15,16]
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