VPS38/UVRAG and ATG14, the variant regulatory subunits of the ATG6/Beclin1-PI3K complexes, are crucial for the biogenesis of the yolk organelles and are transcriptionally regulated in the oocytes of the vector Rhodnius prolixus

In insects the reserve proteins are stored in the oocytes into endocytic-originated vesicles named yolk organelles. VPS38/UVRAG and ATG14 are the variant regulatory subunits of two class-III ATG6/Beclin1 PI3K complexes that regulate the recruitment of the endocytic (complex II) and autophagic (complex I) machineries. In a previous work from our group, we found that the silencing of ATG6/Beclin1 resulted in the formation of yolk-deficient oocytes due to defects in the endocytosis of the yolk proteins. Because ATG6/Beclin1 is present in the two above-described PI3K complexes, we could not identify the contributions of each complex to the yolk defective phenotypes. To address this, here we investigated the role of the variant subunits VPS38/UVRAG (complex II, endocytosis) and ATG14 (complex I, autophagy) in the biogenesis of the yolk organelles in the insect vector of Chagas Disease Rhodnius prolixus. Interestingly, the silencing of both genes phenocopied the silencing of ATG6/Beclin1, generating 1) accumulation of yolk proteins in the hemolymph; 2) white, smaller, and yolk-deficient oocytes; 3) abnormal yolk organelles in the oocyte cortex; and 4) unviable F1 embryos. However, we found that the similar phenotypes were the result of a specific cross-silencing effect among the PI3K subunits where the silencing of VPS38/UVRAG and ATG6/Beclin1 resulted in the specific silencing of each other, whereas the silencing of ATG14 triggered the silencing of all three PI3K components. Because the silencing of VPS38/UVRAG and ATG6/Beclin1 reproduced the yolk-deficiency phenotypes without the cross silencing of ATG14, we concluded that the VPS38/UVRAG PI3K complex II was the major contributor to the previously observed phenotypes in silenced insects. Altogether, we found that class-III ATG6/Beclin1 PI3K complex II (VPS38/UVRAG) is essential for the yolk endocytosis and that the subunits of both complexes are under an unknown transcriptional regulatory system.

Roles of Estrogens in the Healthy and Diseased Oviparous Vertebrate Liver

The liver is a vital organ that sustains multiple functions beneficial for the whole organism. It is sexually dimorphic, presenting sex-biased gene expression with implications for the phenotypic differences between males and females. Estrogens are involved in this sex dimorphism and their actions in the liver of several reptiles, fishes, amphibians, and birds are discussed. The liver participates in reproduction by producing vitellogenins (yolk proteins) and eggshell proteins under the control of estrogens that act via two types of receptors active either mainly in the cell nucleus (ESR) or the cell membrane (GPER1). Estrogens also control hepatic lipid and lipoprotein metabolisms, with a triglyceride carrier role for VLDL from the liver to the ovaries during oogenesis. Moreover, the activation of the vitellogenin genes is used as a robust biomarker for exposure to xenoestrogens. In the context of liver diseases, high plasma estrogen levels are observed in fatty liver hemorrhagic syndrome (FLHS) in chicken implicating estrogens in the disease progression. Fishes are also used to investigate liver diseases, including models generated by mutation and transgenesis. In conclusion, studies on the roles of estrogens in the non-mammalian oviparous vertebrate liver have contributed enormously to unveil hormone-dependent physiological and physiopathological processes.

Autogenous and anautogenous Culex pipiens bioforms exhibit insulin-like peptide signaling pathway gene expression differences that are not dependent upon larval nutrition

Culex pipiens form pipiens and Cx. pipiens form molestus differ in their ability to produce eggs without a bloodmeal. Autogenous mosquitoes, such as the molestus bioform of Cx. pipiens, depend on nutrition acquired as larvae instead of a bloodmeal to fuel the energy intensive process of vitellogenesis, which requires abundant production of yolk proteins. In anautogenous mosquito systems, ovary ecdysteroidogenic hormone (OEH) and insulin-like peptides (ILPs) transduce nutritional signals and trigger egg maturation in response to a bloodmeal. It is unclear to what extent the process is conserved in autogenous mosquitoes and how the bloodmeal trigger has been replaced by teneral reserves. Here, we measured the effects of a series of nutritional regimens on autogeny, time to pupation, and survival in Cx. pipiens form molestus and form pipiens. We find that abundant nutrients never result in autogenous form pipiens and extremely poor food availability rarely eliminates autogeny from form molestus. However, the number of autogenous eggs generated increases with nutrient availability. Similarly, using qPCR to quantify gene expression, we find several differences in the expression levels of ilps between bioforms that are reduced and delayed by poor nutrition, but not extinguished. Changes in OEH expression do not explain bioform-specific differences in autogeny. Surprisingly, the source of most of the gene expression differences correlated with autogeny is the abdomen, not the brain. Overall, our results suggest that autogeny is modulated by nutritional availability, but the trait is encoded by genetic differences between forms and these impact the expression of ILPs.

Receptor-mediated yolk uptake is required for oskar mRNA localization and cortical anchorage of germ plasm components in the Drosophila oocyte

TheDrosophilagerm plasm is responsible for germ cell formation. Its assembly begins with localization ofoskarmRNA to the posterior pole of the oocyte. Theoskartranslation produces 2 isoforms with distinct functions: short Oskar recruits germ plasm components, whereas long Oskar remodels actin to anchor the components to the cortex. The mechanism by which long Oskar anchors them remains elusive. Here, we report that Yolkless, which facilitates uptake of nutrient yolk proteins into the oocyte, is a key cofactor for long Oskar. Loss of Yolkless or depletion of yolk proteins disrupts the microtubule alignment andoskarmRNA localization at the posterior pole of the oocyte, whereas microtubule-dependent localization ofbicoidmRNA to the anterior andgurkenmRNA to the anterior-dorsal corner remains intact. Furthermore, these mutant oocytes do not properly respond to long Oskar, causing defects in the actin remodeling and germ plasm anchoring. Thus, the yolk uptake is not merely the process for nutrient incorporation, but also crucial foroskarmRNA localization and cortical anchorage of germ plasm components in the oocyte.

Nutritional status and fecundity are synchronised by muscular exopheresis

Organismal functionality and reproduction depend on metabolic rewiring and balanced energy resources. However, the crosstalk between organismal homeostasis and fecundity, and the associated paracrine signaling mechanisms are still poorly understood. Using the Caenorhabditis elegans we discovered that large extracellular vesicles termed exophers, attributed in neurons and cardiomyocytes to the removal of damaged subcellular components, are released by body wall muscles to support embryonic growth. We found that exopher formation (exopheresis) is a non-cell autonomous process regulated by egg formation in the uterus. Our data suggest that exophers serve as transporters for muscle-generated yolk proteins used for nourishing and improving the growth rate of the next generation. We propose that the primary role of muscular exopheresis is to stimulate the reproductive capacity, thereby influencing the adaptation of worm populations to the current environmental conditions.