Expression of phase-specific haemolymph polypeptides in a laboratory strain and field catches of Schistocerca gregaria

Uvarov's theory of locust phase polymorphism implies a differential phase-s pecific gene expression. It was the goal of the present investigation to pr ovide data on the molecular level for this concept. We used the technique o f 2D gel electrophoresis to generate haemolymph polypeptide maps from matur e locust males. Under the given conditions we identified 238 polypeptide sp ots by their molecular weight and isoelectrical point. Isolated and crowded males from the Mainz strain, all originating from crowded ancesters, diffe red in 20 spots: three were solitary-specific and 17 crowded-specific. Fiel d catches of solitary and gregarious S. gregaria in Mauritania revealed tha t those males showed the phase-specific expression of the same 20 polypepti de spots as the Mainz strain. (It should be mentioned that the field catche s and the Mainz animals differed in nine spots, but none of them was phase- specific.) As a crosscheck we reared originally solitary field catches for two generations under crowded conditions. This resulted in the repression o f one solitary-specific spot and the expression of 14 gregarious/crowded-sp ecific spots. Since JH conceivably plays a decisive role in the manifestati on of the solitary phase we applied the JH analogue fenoxycarb to crowded M ainz males. 15 days after the treatment nine of the 17 gregarious-specific polypeptide spots were repressed. The fact that experimental manipulations- limited by time-cannot alter the expression of all phase-specific polypepti des may reflect the observation that, in nature, some phase characteristics can change within hours whereas others need several generations. The resul ts provide evidence that a number of haemolymph polypeptides are expressed and repressed, respectively, in relation to phase. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.