Four-way regulation of mosquito yolk protein precursor genes by juvenile hormone-, ecdysone-, nutrient-, and insulin-like peptide signaling pathways

Abstract

Anautogenous mosquito females require a meal of vertebrate blood in order to initiate the production of yolk protein precursors by the fat body. Yolk protein precursor gene expression is tightly repressed in a state-of-arrest before blood meal-related signals activate it and expression levels rise rapidly. The best understood example of yolk protein precursor gene regulation is the vitellogenin-A gene (vg) of the yellow fever mosquito Aedes aegypti. Vg-A is regulated by (1) juvenile hormone signaling, (2) the ecdysone-signaling cascade, (3) the nutrient sensitive target-of-rapamycin signaling pathway, and (4) the insulin-like peptide (ILP) signaling pathway. A plethora of new studies have refined our understanding of the regulation of yolk protein precursor genes since the last review on this topic in 2005 (Attardo et al., 2005). This review summarizes the role of these four signaling pathways in the regulation of vg-A and focuses upon new findings regarding the interplay between them on an organismal level.

Sex Differences: A Resultant of an Evolutionary Pressure?

“…In these organisms, vitellogenin synthesis is under the strict, dual control of gonadal secretion (sperm production) and nutrient levels (through the insulin/IGF-1 signaling (IIS)/daf-2 pathway). In insects (Drosophila or Aedes aegypti), vitellogenin production in the fat body is synergistically regulated by the steroid ecdysone synthesized by the ovarian follicles in response to meal-derived signals and insulin-like peptides via the nutrient sensing protein TOR produced by the fat body (analog of vertebrate liver) (Hansen et al, 2014;Roy et al, 2007). Also in arthropodes the synthesis of vitellogenin occurs in the hepatopancreas under the control of steroid receptors (Girish et al, 2014;Srinivasa Reddy Buchi, 2016;Swetha, 2016).…”

Broadly expressed repressors integrate patterning across orthogonal axes in embryos

“…5H). A role for broadly expressed repressors in the regulation of enhancer timing is likely a conserved mechanism of action and may extend beyond patterning to temporal regulation of gene expression in general (25).…”

Microbiota-Dependent Priming of Antiviral Intestinal Immunity in Drosophila

“…Arthropod-borne viruses (arboviruses) are another group of viruses of global importance. Infection of the insect vector occurs orally during the blood meal, while infection of vertebrate hosts is through an insect bite (Attardo et al, 2005; Hansen et al, 2014; Raikhel and Dhadialla, 1992). Viruses within this blood meal infect intestinal epithelial cells to establish infection, as is the case for many enteric infections in mammals (Davis and Engstrom, 2012; Steinert and Levashina, 2011; Weaver and Barrett, 2004).…”