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The ability of parasites to modify the behaviour of their hosts is a wide spread phenomenon, but the effects of microsporidian parasites on locust behaviour remain unexplored. Here the frequencies of directional changes (ND) and jumping (NJ) per minute of gregarious locusts infected with 2000 spores of the microsporidian parasite Paranosema locustae were significantly different from those of untreated locusts 10 and 16 days after infection, being similar to values for solitary nymphs. In contrast, the behaviour of locusts inoculated with the lower doses of 200 spores/locust was sometimes like that of solitary nymphs. At other times, behaviour was intermediate between solitary and gregarious, i.e. transitional. The rearing density did not affect the turning and jumping behaviour of infected locusts, and their behaviours were similar to those of solitary locusts at 10–16 days after infection. Our study demonstrates that infection with P. locustae may lead gregarious locusts to change some of their behaviour...

Transforming growth factor-beta (TGF-beta) is a multifunctional growth and differentiation factor that affects almost all cells. Although equipotent in many cases, the three isoforms of TGF-beta (-beta1, -beta2, -beta3) have several important isoform specific activities. For example, TGF-beta2 binds with higher affinity to a 60 kDa cell-surface glycosyl phosphatidylinositol (GPI)-linked protein, expressed on vascular endothelial cells. We used chimeric TGF-beta proteins, in which selected regions of TGF-beta1 had been exchanged for the corresponding region of TGF-beta2, to demonstrate that amino acids 67 and 68 regulate binding of TGF-beta to this protein. Exchange of amino acids 67 and 68 of TGF-beta1 into TGF-beta2 resulted in a protein similar in affinity to TGF-beta1 for binding to the GPI-linked protein. In contrast, exchange of only amino acid 67 of TGF-beta1 into TGF-beta2, or exchange of only amino acid 68 of TGF-beta1 into TGF-beta2, resulted in a protein with affinity similar to that of TGF-beta2. This suggests that the coordinated change of Gln and His of TGF-beta1 to Thr and Ile at positions 67 and 68 alters the specificity of TGF-beta. Amino acids 67 and 68 are part of a surface-exposed alpha-helix that forms a projection away from the center of the TGF-beta molecule and is accessible for receptor binding.