No abstract

Within the complex network of chemical signals used by termites, trail pheromones and sex pheromones are among the best known. Numerous recent papers map the chemical identity and glandular origin of these pheromones in nearly all major isopteran taxa. In this study, we aimed to describe the sex pheromone and the trail pheromone of a poorly known sand termite, Psammotermes hybostoma. We identified (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (dodecatrienol) as the sex pheromone released by tergal and sternal glands of female imagos and, at the same time, as the trail pheromone secreted from the sternal gland of workers. We conclude that chemical communication in Psammotermes does not differ from that of most other Rhinotermitidae, such as Reticulitermes, despite the presence of a diterpene as a major component of the trail pheromone of Prorhinotermes to which Psammotermes is presumed to be phylogenetically close. Our findings underline once again the conservative nature of chemical communication in termites, with dodecatrienol being a frequent component of pheromonal signals in trail following and sex attraction and, at the same time, a tight evolutionary relationship between the trail following of working castes and the sex attraction of imagos.

Serine protease inhibitors (PIs) have been described in many plant species and are universal throughout the plant kingdom, where trypsin inhibitors is the most common type. In the present study, trypsin and chymotrypsin inhibitory activity was detected in the seed flour extracts of 13 selected cultivars/accessions of cowpea. Two cowpea cultivars, Cream7 and Buff, were found to have higher trypsin and chymotrypsin inhibitory potential compared to other tested cultivars for which they have been selected for further purification studies using ammonium sulfate fractionation and DEAE-Sephadex A-25 column. Cream7-purified proteins showed two bands on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) corresponding to molecular mass of 17.10 and 14.90 kDa, while the purified protein from Buff cultivar showed a single band corresponding mass of 16.50 kDa. The purified inhibitors were stable at temperature below 60°C and were active at wide range of pH from 2 to 12. The kinetic analysis revealed noncompetitive type of inhibition for both inhibitors against both enzymes. The inhibitor constant (Ki ) values suggested high affinity between inhibitors and enzymes. Purified inhibitors were found to have deep and negative effects on the mean larval weight, larval mortality, pupation, and mean pupal weight of Spodoptera littoralis, where Buff PI was more effective than Cream7 PI. It may be concluded that cowpea PI gene(s) could be potential insect control protein for future studies in developing insect-resistant transgenic plants.

No abstract

The local entomopathogenic bacterium, Bacillus thuringiensis (Bt) was isolated and characterized from 16 soil samples collected from different governorates in Egypt. Among 56 bacterial colonies obtained, only 16 colonies were characterized by traits of Bacillus. All the 16 isolates were toxic to the neonates of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). Damietta and El-Sharkyia bacterial isolates showed appreciable mortality rates (100 and 96.6%), respectively, which were higher than that caused by the standard isolates of Bt entomocidus (that produce Cry1 C toxin) for which they were selected for further characterization. Scanning electron microscope of Damietta bacterial isolate showed the presence of a bipyramidal crystal protein; consistent with the presence of Cry1 toxin class, however, El-Sharkyia bacterial isolate produced spherical-shaped crystals consistent of Cry2 toxin class. Electrophoretic patterns of different isolates and standards revealed different molecular weight bands, ranged from 195 to 8KDa. Damietta and El-Sharkyia bacterial isolates produced major protein bands with molecular weights of 130 KDa, which was also present in Bt entomocidus. Both isolates also shared protein bands with Bt entomocidus with molecular weights of 80, 70, 65, 51, and 22 KDa. The 16S rRNA sequences of both isolates were submitted to the NCBI Gene Bank database, with accession numbers of LC070660 for Damietta isolate and LC070661 for El-Sharkiya isolate. The existence of different Cry genes in the 2 isolates was studied by PCR, using general primers of 5 Cry genes. Cry1 gene was detected in both isolates; however, Cry 2 gene was detected only in Damietta isolate.