Fat body stimulation of ecdysone synthesis in Heliothis zea |
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| Institution: | 1. Department of Entomology, Texas A&M University College Station, TX 77843 U.S.A.;2. Veterinary Toxicology and Entomology Research Laboratory, Agricultural Research Service, USDA College Station, TX 77840, U.S.A.;1. Institute of Applied Chemistry, College of Chemistry, Xin Jiang University, Urumqi 830046, Xin Jiang, PR China;2. Key Laboratory of Advanced Functional Materials, Autonomous Region, Urumqi 830046, Xin Jiang, PR China;3. State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xin Jiang University, Urumqi 830046, Xin Jiang, PR China;4. Key Laboratory of Petroleum and Gas Fine Chemicals, Educational Ministry of China, College of Chemical Engineering, Xin Jiang University, Urumqi 830046, Xin Jiang, PR China;5. State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, Educational Ministry of China, College of Chemical Engineering, Xin Jiang University, Urumqi 830046, Xin Jiang, PR China;1. Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China;2. Department of Crop Protection, Ghent University, B-9000 Ghent, Belgium |
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| Abstract: | Prothoracic glands of Heliothis zea pupae require both a humoral factor and prothoracicotropic hormone (PTTH) to synthesize ecdysone. The humoral factor is absent when pupae are maintained at diapause-sustaining temperatures. Thus, pupae remain in diapause despite the release of PTTH at or before larval-pupal ecdysis.Tissue implantation experiments revealed that a diapause-terminating factor is present in the fat body of non-diapausing pupae. Other tissue implantation experiments showed that, when diapausing pupae were transferred from 19 to 27°C, diapause-terminating activity appeared first in the fat body and then the fat body into the haemolymph. HPLC separation of the haemolymph and fat body fractions followed by bioassay demonstrated that fractions containing diapause-terminating activity eluted from both tissues within 28–30 min. These results suggest that the factors found in the fat body and haemolymph may be the same compound.Evidence from ecdysone radioimmunoassay experiments ruled out the possibility that the diapauseterminating activity was due to either free or conjugated ecdysteroids. Corresponding in vitro experiments in which the prothoracic glands were cultured with brain extracts versus fat body and haemolymph fractions also indicated that the haemolymph/fat body factor was not PTTH. |
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