Silencing of RpATG6 impaired the yolk accumulation and the biogenesis of the yolk organelles in the insect vector R. prolixus. 2018

Priscila H Vieira, and Larissa Bomfim, and Georgia C Atella, and Hatisaburo Masuda, and Isabela Ramos
Laboratório de Bioquímica de Insetos, Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.

In oviparous animals, the egg yolk is synthesized by the mother in a major metabolic challenge, where the different yolk components are secreted to the hemolymph and delivered to the oocytes mostly by endocytosis. The yolk macromolecules are then stored in a wide range of endocytic-originated vesicles which are collectively referred to as yolk organelles and occupy most of the mature oocytes cytoplasm. After fertilization, the contents of these organelles are degraded in a regulated manner to supply the embryo cells with fundamental molecules for de novo synthesis. Yolk accumulation and its regulated degradation are therefore crucial for successful development, however, most of the molecular mechanisms involved in the biogenesis, sorting and degradation of targeted yolk organelles are still poorly understood. ATG6 is part of two PI3P-kinase complexes that can regulate the recruitment of the endocytic or the autophagy machineries. Here, we investigate the role of RpATG6 in the endocytosis of the yolk macromolecules and in the biogenesis of the yolk organelles in the insect vector Rhodnius prolixus. We found that vitellogenic females express high levels of RpATG6 in the ovaries, when compared to the levels detected in the midgut and fat body. RNAi silencing of RpATG6 resulted in yolk proteins accumulated in the vitellogenic hemolymph, as a consequence of poor uptake by the oocytes. Accordingly, the silenced oocytes are unviable, white (contrasting to the control pink oocytes), smaller (62% of the control oocyte volume) and accumulate only 40% of the yolk proteins, 80% of the TAG and 50% of the polymer polyphosphate quantified in control oocytes. The cortex of silenced oocytes present atypical smaller vesicles indicating that the yolk organelles were not properly formed and/or sorted, which was supported by the lack of endocytic vesicles near the plasma membrane of silenced oocytes as seen by TEM. Altogether, we found that RpATG6 is central for the mechanisms of yolk accumulation, emerging as an important target for further investigations on oogenesis and, therefore, reproduction of this vector.

UI MeSH Term Description Entries
D007303 Insect Vectors Insects that transmit infective organisms from one host to another or from an inanimate reservoir to an animate host. Insect Vector,Vector, Insect,Vectors, Insect
D004530 Egg Yolk Cytoplasm stored in an egg that contains nutritional reserves for the developing embryo. It is rich in polysaccharides, lipids, and proteins. Egg Yolks,Yolk, Egg,Yolks, Egg
D005260 Female Females
D000071186 Beclin-1 An autophagy related protein which functions as a core subunit of PHOSPHATIDYLINOSITOL 3-KINASE MULTIPROTEIN COMPLEXES. It mediates the formation of phosphatidylinositol 3-phosphate and functions in AUTOPHAGY, where it is required for maturation of the AUTOPHAGOSOME. It also functions in ENDOCYTOSIS and CYTOKINESIS as part of a separate complex. Beclin-1 associates with INTRACELLULAR MEMBRANES and interacts with the PROTO-ONCOGENE PROTEINS C-BCL-2 and BCL-X PROTEIN. ATG-6 Protein,ATG6 Protein,Beclin-1 Protein,Beclin1,Coiled-coil Myosin-like Bcl2-interacting Protein,GT197 Protein,ATG 6 Protein,Beclin 1,Beclin 1 Protein,Coiled coil Myosin like Bcl2 interacting Protein
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012239 Rhodnius A genus of the subfamily TRIATOMINAE. Rhodnius prolixus is a vector for TRYPANOSOMA CRUZI.
D015388 Organelles Specific particles of membrane-bound organized living substances present in eukaryotic cells, such as the MITOCHONDRIA; the GOLGI APPARATUS; ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES. Organelle
D019476 Insect Proteins Proteins found in any species of insect. Insect Protein,Protein, Insect,Proteins, Insect
D020868 Gene Silencing Interruption or suppression of the expression of a gene at transcriptional or translational levels. Gene Inactivation,Inactivation, Gene,Silencing, Gene

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