Ground-based studies with Super-Dwarf wheat in preparation for space flight.

Several experiments were carried out to test responses of a Super-Dwarf cultivar of wheat (Triticum aestivum L.) to various environmental parameters that were anticipated to be present in our attempts to grow the wheat in a small growth chamber on the Russian Space Station, Mir, or that proved to be present in a 1995 trial space experiment. Under low photosynthetic photon flux (40-400 micromoles m-2 s-1 PPF), development (e.g. anthesis) was retarded, but heads (often sterile) always formed, even if light was so low that plants died before the heads could mature. Longer photoperiods promoted flowering, but night interruptions combined with short days did not provoke a long-day response as occurs with true long-day plants. The long-day effect could prove to be a summation of photosynthetic products. Heat stress (40 degrees C for 1-24 h) did not influence flowering but killed plants that were 13-16-day-old (no effect on younger plants). Concentrations of iodine or silver-fluoride disinfectants present in the water used for plants on Mir (1.0-4.0 mg L-1) did not affect plant growth although higher concentrations (8.0-1.6 mg L-1) were inhibitory. GA3 or indoleacetic acid applied every other day at concentrations from 1.0 x 10(-6) mg L-1 to 3.162 x 10(-4) mg L-1 did not change the height of Super-Dwarf wheat, suggesting that this cultivar is not a gibberellin mutant.

Expression of biologically active human antithrombin III by recombinant baculovirus in Spodoptera frugiperda cells.

Antithrombin III (ATIII) is a plasma-borne serine protease inhibitor that plays a pivotal role in the regulation of hemostasis. The cDNA for ATIII has been available, but genetic studies on the functional domains of ATIII have not progressed because of the absence of an expression system that will yield sufficient quantities of biologically active protein for biochemical analyses. In the present studies the cDNA of the human antithrombin III gene was inserted into the vector pVL 1393, which is suitable for cotransfection of Spodoptera frugiperda (Sf9) insect cells with Baculovirus wild-type DNA. Recombinant virus particles were selected by the presence of occlusion-negative plaques. Upon infection with purified recombinant virus, Sf9 cells secreted 10-35 micrograms of ATIII/1 x 10(6) cells. Southern analysis of DNA from infected cells demonstrated incorporation of the full-length cDNA into the Baculovirus recombinant, and RNase protection experiments verified the presence of full-length transcript. This recombinant ATIII protein was immunologically reactive with antisera raised against native human ATIII, formed stable complexes with thrombin, and was heparin-accelerated at the same concentration as native human ATIII. In addition, the recombinant ATIII retained specificity for the same molecular species of heparin that activates authentic human ATIII. This is the first successful production of active, recombinant ATIII in quantities that will allow purification on the milligram scale and permit a biochemical analysis of genetically engineered variants.