HATLE, John D.; DING , Xiang; BARRY, Thomas O.; BORST, David W.; Univ. of North Florida; Illinois State Univ.; Illinois State Univ.; Illinois State Univ.: Storage protein levels in lubber grasshoppers are not regulated by juvenile hormone

Hemolymph storage proteins (SPs), especially methionine-rich SPs, are negatively regulated by juvenile hormone (JH) in several insects. In the lubber grasshopper (Romalea microptera), three proteins that compose >80% of total hemolymph protein appear to be SPs. Sequence analysis (by LC-MS) showed that all three proteins have the DYDTFYK consensus sequence common among insect SPs. Furthermore, the amino acid composition of these proteins suggests that SP 522 (i.e., MW = 522) is similar to the persistent SP of Locusta migratoria, SP 275 is a methionine-rich SP, and SP 92 is an arylphorin. Finally, during oocyte development the maximum level of JH is followed by a ~50% decline in total hemolymph protein. Therefore, we hypothesized that JH negatively regulates SPs in adult female lubbers. To test this hypothesis, the corpora allata (the source of JH) were surgically removed from 5-d female grasshoppers. After ~14 d, these animals were injected every ~6 d with 500 �g methoprene (JH analog) or the vehicle (mineral oil) alone. Hemolymph samples were collected before each injection. We quantified SPs by densitometric analysis of Coomassie-stained native PAGE gels and vitellogenin (Vg) by ELISA (detection range = 0.2 � 29 mg/ml). Grasshoppers treated with vehicle had < 0.2 mg/ml Vg throughout the experiment. In grasshoppers treated with methoprene, Vg levels rose to high levels (> 17 mg/ml) after 26 days and remained high until the end of the experiment. In contrast, all three SPs were present throughout the experiment in vehicle- and methoprene-treated animals and their levels were similar, ranging from 16 � 55 mg/ml. We conclude that JH does not negatively regulate SPs in adult female lubbers. (Supported by NSF grant DBI – 9978810 to DWB)