title: Calcium-regulated fusion of yolk granules is important for yolk degradation during early embryogenesis of Rhodnius prolixus Stahl.
abstract: This study examined the process of membrane fusion of yolk granules (YGs) during early embryogenesis of Rhodnius prolixus. We show that eggs collected at days 0 and 3 after oviposition contain different populations of YGs, for example day-3 eggs are enriched in large YGs (LYGs). Day-3 eggs also contain the highest free [Ca(2+)] during early embryogenesis of this insect. In vitro incubations of day-0 YGs with [Ca(2+)] similar to those found in day-3 eggs resulted in the formation of LYGs, as observed in vivo. Fractionation of LYGs and small YGs (SYGs) and their subsequent incubation with the fluorescent membrane marker PKH67 showed a calcium-dependent transference of fluorescence from SYGs to LYGs, possibly as the result of membrane fusion. Acid phosphatase and H(+)-PPase activities were remarkably increased in day-3 LYGs and in calcium-treated day-0 LYGs. Both fractions were found to contain vitellins as major components, and incubation of YGs with calcium induced yolk proteolysis in vitro. Altogether, our results suggest that calcium-induced membrane fusion events take part in yolk degradation, leading to the assembly of the yolk mobilization machinery.
authors.affiliation: Laboratório de Entomologia Médica, Instituto de Biofísica Carlos Chagas Filho (IBCCF), Universidade Federal do Rio de Janeiro (UFRJ), Cidade Universitária--Ilha do Fundão, 21941-590 Rio de Janeiro, RJ, Brasil.
authors.forename: I B
authors.initials: IB
authors.lastname: Ramos
authors.forename: K
authors.initials: K
authors.lastname: Miranda
authors.forename: W
authors.initials: W
authors.lastname: de Souza
authors.forename: D M P
authors.initials: DM
authors.lastname: Oliveira
authors.forename: A P C A
authors.initials: AP
authors.lastname: Lima
authors.forename: M H F
authors.initials: MH
authors.lastname: Sorgine
authors.forename: E A
authors.initials: EA
authors.lastname: Machado
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004527:Egg Proteins / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D047108:Embryonic Development; D006867:Hydrolases / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D010063:Ovum / Q000166:cytology*; D017494:Proton Pumps / Q000378:metabolism; D012239:Rhodnius / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D047048:Vitellins / Q000378:metabolism
chemical_list: D004527:Egg Proteins; D017494:Proton Pumps; D047048:Vitellins; D006867:Hydrolases; D002118:Calcium