Pollination, breeding system, and genetic structure in two sympatric Delphinium (Ranunculaceae) species.

Two sympatric Delphinium species, D. barbeyi and D. nuttallianum, are ecologically and morphologically similar. However, D. barbeyi has multiple, large inflorescences while D. nuttallianum has a single, small inflorescence. These differences in floral display should result in greater intraplant pollen transfer in D. barbeyi, leading to higher rates of self-pollination through geitonogamy. Reduced gene flow by pollen should in turn produce greater population differentiation among populations of D. barbeyi relative to D. nuttallianum. We tested these predictions by comparing pollinator behavior, breeding systems, outcrossing rates, and population genetic structure of sympatric populations of the two species in Colorado. Bumble bee and hummingbird pollinators visit more flowers and inflorescences per foraging bout in D. barbeyi than in D. nuttallianum. The species differed in breeding system; D. barbeyi produced more seeds by autogamy (9 vs. 2%) than D. nuttallianum and suffered no reduction in seed set in hand-self vs. outcross pollinations, in contrast to a 41% decline in D. nuttallianum. The outcrossing rate in one D. barbeyi population was 55%, but ranged from 87 to 97% in four D. nuttallianum populations. Genetic differentiation among population subdivisions estimated by hierarchical F statistics was >10 times greater in D. barbeyi ( = 0.055-0.126) than D. nuttallianum ( = 0.004-0.009) at spatial scales ranging from metres to 3.5 km. Spatial autocorrelation analysis also indicated more pronounced local genetic structure in D. barbeyi than D. nuttallianum populations. Fixation indices (F(IS)) of D. barbeyi adults were much lower than expected based on mating system equilibrium and suggest that differences in the degree of self-compatibility and/or the timing of postpollination selection/inbreeding depression between the two species further contribute to the genetic differences between them.

Effects of thrombospondin purified by heparin affinity or ion-exchange chromatography on the alternative complement pathway.

Thrombospondin (TSP), a platelet glycoprotein, was purified from platelet supernatants applied sequentially to Sepharose 4B and heparin-agarose affinity columns. This TSP inhibited alternative pathway activity in serum as assessed by lysis of rabbit erythrocytes and contained bound heparin, a substance which is known to inhibit the alternative pathway. TSP purified by anion exchange chromatography did not contain heparin and was not inhibitory. Chromatography of this TSP over a heparin-agarose affinity column resulted in TSP which contained heparin and inhibited the alternative pathway. Purification of TSP by the standard technique of heparin affinity chromatography results in preparations which are contaminated with heparin.

Early changes in the synthesis of proteins with affinity for single-stranded DNA during the onset of transformation in NRK cells.

Early alterations in the synthesis of proteins which bind to single-stranded DNA have been examined following the onset of transformation in NRK cells transformed by a heat-sensitive mutant (ts339) of Rous sarcoma virus. Transformation was initiated by shifting quiescent cultures from nonpermissive to permissive temperatures. Cultures were prelabelled with [3H]leucine for several generations at the non-permissive temperature, and with [35S]methionine at times after shift to the permissive temperature. Cytosol extracts were passed through sequential columns of double-stranded and single-stranded DNA bound to cellulose. Within the first hour of transformation there was an increase in the synthetic rate of proteins binding tightly to single-stranded DNA, but not to double-stranded DNA. More loosely bound protein fractions showed no such early synthetic increase. Electrophoresis of the fraction eluted from single stranded DNA-cellulose with 2 M NaCl demonstrated the presence of a major protein of 93 000 daltons, which comprised more than 0.1% of the cytosol protein. The synthesis of the 93 000 dalton protein increased continuously over the first 4 h interval after the onset of transformation. The synthetic rate of a 35 000 dalton protein, a major DNA-binding polypeptide found in mammalian cells, began to increase after a 1-h lag, following the onset of transformation. The protein fraction containing the 93 000 dalton protein had considerable unwinding activity, depressing the melting temperature of poly(dA-dT) by 39 degrees C. The protein fraction containing the bulk of the 35 000 dalton protein did not have unwinding activity. Transformation-induced DNA synthesis was measured in cells made permeable to deoxyribonucleoside triphosphates at times after shift to the permissive temperature. It was determined that synthesis of DNA began within the first 1--2 h after the onset of transformation. We conclude that the early transformation-associated synthesis of SS93 and perhaps other proteins binding to single-stranded DNA may be related to early transformation-associated changes preparatory to DNA replication and subsequent growth.