Biochemical and cytoimmunological evidence for the control of Aedes aegypti larval trypsin with Aea‐TMOF

Abstract

Trypsin and chymotrypsin-like enzymes were detected in the gut of Aedes aegypti in the four larval instar and pupal developmental stages. Although overall the amount of trypsin synthesized in the larval gut was 2-fold higher than chymotrypsin, both enzymes are important in food digestion. Feeding Aea-Trypsin Modulating Oostatic Factor (TMOF) to Ae. aegypti and Culex quinquefasciatus larvae inhibited trypsin biosynthesis in the larval gut, stunted larval growth and development, and caused mortality. Aea-TMOF induced mortality in Ae. aegypti, Cx. quinquefasciatus, Culex nigripalpus, Anopheles quadrimaculatus, and Aedes taeniorhynchus larvae, indicating that many mosquito species have a TMOF-like hormone. The differences in potency of TMOF on different mosquito species suggest that analogues in other species are similar but may differ in amino acid sequence or are transported differently through the gut. Feeding of 29 different Aea-TMOF analogues to mosquito larvae indicated that full biological activity of the hormone is achieved with the tetrapeptide YDPA. Using cytoimmunochemical analysis, intrinsic TMOF was localized to ganglia of the central nervous system in larvae and male and female Ae. aegypti adults. The subesophageal, thoracic, and abdominal ganglia of both larval and adult mosquitoes contained immunoreactive cells. Immunoreactive cells were absent in the corpus cardiacum of newly molted 4th instar larvae but were found in late 4th instar larvae. In both males and females, the intrinsic neurosecretory cells of the corpus cardiacum were filled with densely stained immunoreactive material. These results indicate that TMOF-immunoreactive material is synthesized in sugar-fed male and female adults and larvae by the central nervous system cells.

A viral chitinase enhances oral activity of TMOF

“…The same studies also clearly showed a strong increase of the permeability to molecules of the PMs treated in vitro with ChiA. These results stimulated the idea of using ChiA in combination with Aea-TMOF, which targets receptors expressed in the basolateral membrane of epithelial midgut cells and causes the inhibition of trypsin synthesis, thus impairing the insect digestive processes (Borovsky et al, 1994;Nauen et al, 2001;Borovsky and Meola, 2004). Aea-TMOF exerts mild insecticide activity on Heliothis virescens larvae when expressed in transgenic tobacco plants (Tortiglione et al, 2002;2003), and negatively interferes with larval growth of the tobacco budworm (Heliothis virescens), when fused to Tobacco…”

Synergy Between Aedes aegypti Trypsin Modulating Oostatic Factor and δ-Endotoxins

“…aegypti larvae are 6-35 fold more sensitive to Bti toxins than well-fed larvae ( Table 1), and starved 1 st instar larvae are 10-fold more sensitive than 3 rd instars. Since TMOF is more effective against 1 st and 2 nd instar larvae [9], the use of both toxins in early developmental stages is expected to enhance the effect of low toxin doses and reduce the amount of Bti required in sewage treatment ponds in which it is not effective alone.…”

“…TMOF expressed on the coat protein of Tobacco Mosaic Virus that was fed to mosquito larvae caused anorexia and death at a low dose (1 ng per larva) [4]. Thus, orally fed TMOF can be used as an effective larvicide against many mosquito species [4,9]. Using a synthetic TMOF to control mosquito larvae is, however, expensive and inefficient because it is readily soluble in water, whereas mosquito larvae are filter feeders [10].…”

Expression of Aedes trypsin-modulating oostatic factor on the virion of TMV: A potential larvicide

“…Mosquito ovaries synthesize and release TMOF into the hemolymph after a blood meal (11), and the hormone modulates the synthesis of trypsin in the mosquito gut by binding a TMOF receptor (12). Cytoimmunochemical studies showed that TMOF is also found in the brain and the neuroendocrine organs of adult and larval Aedes aegypti (13). Thus, the hormone has a dual role in terminating serine-proteases biosynthesis not only in adult female mosquitoes but also in larvae (13).…”

“…Cytoimmunochemical studies showed that TMOF is also found in the brain and the neuroendocrine organs of adult and larval Aedes aegypti (13). Thus, the hormone has a dual role in terminating serine-proteases biosynthesis not only in adult female mosquitoes but also in larvae (13). Mosquito TMOF or its analogues stop trypsin biosynthesis in the cat flea Ctenocephalides felis, in the stable fly Stomoxys calcitrans, in the house fly Musca domestica, in the midge Culicoides variipenis, and in H. virescens (8)(9)(10).…”