Vitellins and vitellogenins of Dysdercus koenigii (Heteroptera: Pyrrhocoridae)--identification, purification and temporal pattern

Molecular characterization of vitellin from the ovaries of the white shrimp Penaeus (Litopenaeus) vannamei

Vitellin (Vt) was purified from ovary extracts of mature females of the white shrimp Penaeus vannamei using Sepharose CL-4B and Q-Sepharose columns. Native Vt had an apparent molecular weight of 388 kDa as detected in Native-PAGE, bound the lipophilic dye Oil Red O and had a total lipid content of approximately 43.8%. Under reducing and denaturing conditions (SDS-PAGE), Vt is composed of three major subunits of 87, 78 and 46 kDa, although minor bands of 65, 61 and 31 kDa are also detected. The 87- and 78-kDa polypeptides were strongly recognized by Penaeus semisulcatus anti-Vt polyclonal and Penaeus monodon anti-Vt monoclonal antibodies. Furthermore, the N-terminal amino acid sequence of the 78-kDa polypeptide is very similar to Penaeus japonicus vitellogenin (Vg) and P. semisulcatus Vt, with an identity of 76%. Circular dichroism indicates that the beta-helix content of Vt is 25% while beta-sheets correspond to 37 and 14% of unordered secondary structure. These values are similar to insect microvitellogenin. Vt has an emission fluorescence maximum at 329 nm, comparable to the shrimp high-density lipoprotein/beta-glucan binding protein (HDL/BGBP).

Molecular characterization of the bifunctional VHDL-CP from the hemolymph of white shrimp Penaeus vannamei

A very high-density lipoprotein (VHDL) purified from the hemolymph of the white shrimp Penaeus vannamei is shown to be identical to the clotting protein (CP) previously reported from the same organism based on size, subunits and N-terminal amino acid sequence. The approximately 440-kDa protein, a homodimer of approximately 200-kDa subunits, was present in KBr gradient fractions ranging in density from 1.155 to 1.212 g/ml. Samples of VHDL after purification by strong cation exchange chromatography were subjected to electrophoresis on native polyacrylamide gels. Lipids associated with the VHDL were detected by Sudan Black and Oil Red O staining and comprise 9-15% of the purified protein. Circular dichroism of VHDL-CP indicates that the alpha-helix content of the VHDL-CP is 32%, while beta-sheets correspond to 33%, closely resembling the secondary structure of CP from the shrimp Penaeus monodon and, remarkably, the secondary structure of very high-density lipophorin E (VHDLpE) from the tobacco hornworm, Manduca sexta.

Purification and characterization of the common yolk protein, vitellin, from the estuarine amphipod Leptocheirus plumulosus

Vitellin is a major yolk protein that plays a significant role in the embryonic development of crustacean embryos. This protein was rapidly purified from embryos of the estuarine amphipod, Leptocheirus plumulosus, by subjecting the crude protein homogenate to high affinity column chromatography. SDS-PAGE revealed a single band with an approximate molecular weight of 200,000 daltons. Vitellin was characterized by SDS-PAGE techniques and amino acid composition analysis. L. plumulosus vitellin is a lipoglycophosphoprotein with serine, glutamic acid/glutamine, alanine, and aspartic acid/asparagine accounting for almost 66% of all amino acid residues. Polyclonal antibodies were raised against L. plumulosus vitellin and antibody reactivity was verified by dot-blotting and immuno-fluorescence confocal microscopy. These antibodies are specific for purified vitellin and show little cross-reactivity with other embryonic proteins.

Effect of age, diet, diapause and juvenile hormone on oogenesis and the amount of vitellogenin and vitellin in the twospotted stink bug, Perillus bioculatus (Heteroptera: pentatomidae)

Vitellogenic oocytes from Perillus bioculatus have two native vitellins, Vt1 and Vt2, with molecular masses of 553 and 228 kDa, respectively. The hemolymph contains a major vitellogenin, Vg, with a molecular mass of 528 kDa that consists of three apoproteins with masses of 177, 84 and 59 kDa, respectively. Antibodies to purified Vt2 reacted with ovary extracts, egg extracts and female hemolymph, but not with male hemolymph in immunodiffusion tests. Western blots showed that anti Vt2 reacted with both Vt1, Vt2 and with Vg. Vitellogenesis starts at an ovarian score of 12 at 2.4 days after emergence. The first cycle of egg development is completed in ovaries with a score of 112 at 7.7 days. During this 5.3 day period, the ovaries of a single female incorporated 1833 &mgr;g of protein to form vitellin. Vitellogenin levels start to increase in females 2.5 days after emergence and reached 17.8 &mgr;g/&mgr;l by 5.5 days. After 5.5 days vitellogenin levels fluctuated between 9.7 and 19.9 &mgr;g/&mgr;l. Most diapausing females contained no ovarian follicles in the vitellarium and their hemolymph contained less than 1 &mgr;g/&mgr;l of vitellogenin. Treating diapausing females with 1 &mgr;g of JH III increased vitellogenin levels over 120-fold. Insects maintained on a liver-based artificial diet had lower vitellogenin levels than the controls at all sample times and did not show an increase in vitellogenin concentration until 11.5 days. Treating insects on the artificial diet with 10 &mgr;g of JH III elevated vitellogenin levels to about a fourth of that found in prey-fed insects of a comparable age. This suggests that females fed the artificial diet have low levels of essential materials needed for vitellogenin production.

Role of juvenile hormone in the synthesis and sequestration of vitellogenins in the red cotton stainer, Dysdercus koenigii (Heteroptera: Pyrrhocoridae)

Investigations were carried out to determine the role of juvenile hormone (JH) and 20-hydroxy ecdysone in the synthesis and uptake of vitellogenins, which were earlier identified, purified and characterised, in Dysdercus koenigii. The concentration(s) of vitellogenin(s) in fat body, haemolymph and that of vitellin(s) in ovary were significantly lower after chemical allatectomy at eclosion. In addition, at 70 h after emergence, chemical allatectomy reduced ovarian vitellin concentration, but vitellogenin levels remained normal in the fat body and haemolymph. The haemolymph vitellogenins were not incorporated into oocytes in such insects. Administration of JH-III at 20 h after allatectomy restored vitellogenin levels in the fat body and haemolymph, but the ovary failed to incorporate the available vitellogenins from haemolymph in such insects. However, when JH-III was administered twice, one at 20 h and then at 70 h after allatectomy, vitellogenin concentrations in fat body and haemolymph and also vitellin concentrations in ovary approached control levels. It is suggested that JH has two separate roles, one in vitellogenin synthesis and the other in uptake. 20-hydroxy ecdysone had no apparent role in either vitellogenin synthesis or uptake in D. koenigii.

Vitellin and vitellogenin in the soldier bug, Podisus maculiventris: identification with monoclonal antibodies and reproductive response to diet

A 171,000 M(r )polypeptide of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) that constituted 16% of the protein in eggs also constituted up to 25% of the protein in hemolymph of fed females. It was identified as the major or sole apoprotein of vitellogenin. Eggs contained major polypeptides of 171, 106, and 51 kDa. The hemolymph polypeptide was identified with a polypeptide (vitellin) in egg extracts by comparing molecular weights, specificity of occurrence in fed females, and immunological reactivities. Females, starved for 5 days after eclosion to assure complete previtellogenic development, produced vitellogenin within a day after feeding on larval Galleria mellonella, and within 4 days after feeding on an artificial diet. Appearance of vitellogenin preceded ovarian growth by 2-3 days. Two monoclonal antibodies raised against egg proteins of P. maculiventris were selected for their strong reaction against egg extract and female hemolymph and null reaction against male hemolymph. Only one 170-kDa band in egg and hemolymph reacted with the antibodies on denaturing Western blots. These monoclonal antibodies are being used to develop an enzyme-linked immunosorbent assay (ELISA) to quantitate reproductive response of females to diets of differing quality.