Hexamerin a Novel Protein Associated with Bacillus sphaericus Resistance in Culex quinquefasciatus

Abstract

Bacterial insecticides like, Bacillus sphaericus and Bacillus thuringiensis serovar israelensis, have been used for the control of nuisance and vector mosquitoes for more than two decades. For many years, it was assumed that the use of microbial larvicides based on B. sphaericus would not lead to resistance in mosquitoes. However, recent reports have shown that B. sphaericus toxins are not free from this problem. Therefore, the resistance of mosquito populations to be will seriously threaten the sustainability of current mosquito control programme using these microbial insecticides. In the present study, we have characterised a novel protein responsible for resistance development in the filariasis vector of Culex quinquefasciatus. Laboratory selection experiments with B. sphaericus against the larvae were carried out up to 17 generations, and the occurrence of resistance was reported (resistance ratio (RR) at lethal concentration (LC)50 and LC90 = 1,987 and 2,051 folds, respectively). The protein profiles of B. sphaericus-resistant and susceptible population have confirmed with the expression of a new polypeptide (80 kDa) in the resistant strain only. Sequence result revealed that the newly expressed protein was 'hexamerin', and this factor might conceivably be responsible for the inheritance of resistance. This study is therefore valuable for comprehending the underlining factor and management of B. sphaericus resistance problem in mosquito population.

Bombyx mori and Aedes aegypti form multi-functional immune complexes that integrate pattern recognition, melanization, coagulants, and hemocyte recruitment

“…Three different storage proteins were also identified. We tentatively classified these as coagulants given their propensity to form hexamers and larger order multi-hexamers, and their numerous reported immune functions [ 26 – 30 ]. Pattern recognition proteins with likely immune functions were also found, including two lectins, C-type 19 and C-type 21, and multiple members of the large 30 kD lipoprotein family (Bm Lp2, Lp4, Lp5, Lp6, and Lp15), none of which have been previously recognized as forming high mass aggregates.…”

Alkaline phosphatases are involved in the response of Aedes aegypti larvae to intoxication with Bacillus thuringiensis subsp. israelensis Cry toxins

“…An increased production of hexamerins was observed in Helicoverpa armigera larvae exposed to sublethal doses of Cry1Ac, resulting in an aggregation reaction with the toxin supposedly to inactivate it (Ma et al ., ). In the mosquito C. quinquefasciatus , hexamerins have been associated with resistance to Bacillus sphaericus , but their role in response to Bti toxins is yet to be understood (Poopathi et al ., ). Genes located in lipid rafts were over‐transcribed after Bti exposure.…”

A novel hexamerin with an unexpected contribution to the prophenoloxidase activation system of the Chinese oak silkworm, Antheraea pernyi

“…To date, accumulating evidence has shown the involvement of hexamerin in insect immune responses, for instance, the hexamerins in Culex quinquefasciatus (Poopathi et al, 2014) and Anopheles gambiae (Lombardo & Christophides, 2016). It is of interest to note that hexamerin in C. haematoceps was involved in PPO activation (Eliautout et al, 2016), but the molecular mechanism by which hexamerin upregulated PO activity remains to be elucidated.…”

“…Most of the storage proteins are identified as hexamerins, a group of respiratory hemocyaninderived proteins that lost the ability to transport oxygen (Burmester, 2002;Telfer & Kunkel, 1991). A number of hexamerins have been identified in arthropods (Burmester, 2015;Cristino et al, 2010;Cunha, Nascimento, Guidugli, Simoes, & Bitondi, 2005;Liang, Xie, & Luan, 2019;Martins & Bitondi, 2012;Pick, Hagner-Holler, & Burmester, 2008;Tsai, Chen, & Tsai, 2014), but research in recent decades has demonstrated that in addition to providing energy as storage proteins in the nonfeeding stage, hexamerins also take part in many other physiological processes, including egg production (Wheeler, Tuchinskaya, Buck, & Tabashnik, 2000), hormone transport (Ashfaq, Sonoda, & Tsumuki, 2007;Rao, Ningshen, Chaitanya, Senthilkumaran, & Dutta-Gupta, 2016), caste regulation (Hawkings, Calkins, Pietrantonio, & Tamborindeguy, 2019;Zhou, Tarver, Bennett, Oi, & Scharf, 2006), diapause (Spiliotopoulos, Gkouvitsas, Fantinou, & Kourti, 2007), and even immune responses (Fallon, Troy, & Kavanagh, 2011;Poopathi et al, 2014;Tang, Wang, & Zhang, 2010).…”