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Front. Physiol. | doi: 10.3389/fphys.2019.00122

Biochemical and functional characterization of Glycoside Hydrolase Family 16 genes in Aedes aegypti larvae: identification of the major digestive Beta-1,3-glucanase

 Raquel S. Souza1,  Maiara D. Faria Gama1, Renata Schama1, José B. Pereira Lima1,  Hector M. Diaz-Albiter2 and  Fernando A. Genta1*
  • 1Fundação Oswaldo Cruz (Fiocruz), Brazil
  • 2University of Glasgow, United Kingdom

Insect β-1,3-glucanases belong to Glycoside Hydrolase Family 16 (GHF16) and are involved in digestion of detritus and plant hemicellulose. In this work, we investigated the role of GHF16 genes in Aedes aegypti larvae, due to their detritivore diet. The genome of Ae. aegypti contains six genes coding for GHF16 proteins (Aae GH16.1 - Aae GH16.6), containing 2-6 exons. Phylogenetic analysis suggests that Aae GH16.1, 2, 3, 5 and 6, which contain the GHF16 conserved catalytic residues, are related to other insect glucanases. These genes suffered duplications in the genomes of Nematocera. Aae GH16.4 is related to β-1,3-glucan binding proteins, which have no catalytic activity and are involved in the activation of innate immune responses.
Additionally, Ae. aegypti larvae contain significant β-1,3-glucanase activities in the head, gut and rest of body. These activities have optimum pH about 5-6 and molecular masses between 41 and 150 kDa. All GHF16 genes above showed different levels of expression in the larval head, gut or rest of the body. Knock-down of AeGH16.5 resulted in survival and pupation rates lower than controls (dsGFP and water treated). However, under stress conditions, severe mortalities were observed in AeGH16.1 and AeGH16.6 knocked-down larvae. Enzymatic assays of β-1,3-glucanase in AeGH16.5 silenced larvae exhibited lower activity in the gut and no change in the rest of the body. Chromatographic activity profiles from gut samples after GH16.5 silencing showed suppression of enzymatic activity, suggesting that this gene codes for the digestive larval β-1,3-glucanase of Ae. aegypti. This gene and enzyme are attractive targets for new control strategies, based on the impairment of normal gut physiology.

Keywords: Aedes aegypti, Beta-1,3-glucanase, Knock-down, Digestion, Immunity, Glycoside hydrolase family 16, GHF16

Received: 03 Jul 2018; Accepted: 31 Jan 2019.

Edited by:

Senthil-Nathan Sengottayan, Manonmaniam Sundaranar University, India

Reviewed by:

Muthugounder S. Shivakumar, Periyar University, India
Najmeh Sahebzadeh, Zabol University, Iran
Marcela B. Figueiredo, Swansea University, United Kingdom  

Copyright: © 2019 Souza, Faria Gama, Schama, Pereira Lima, Diaz-Albiter and Genta. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: PhD. Fernando A. Genta, Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil, gentafernando@gmail.com