Genetic Variation in Fundulus heteroclitus: Geographic Distribution

Studies of 16 polymorphic loci in the fish Fundulus heteroclitushave uncovered significant directional changes in gene frequencieswith latitude (i.e., clines). These spatial patterns could havearisen by primary and/or secondary intergradation. While wecannot presently distinguish between these two models, mitochondrialDNA analyses indicate that if previous isolation occurred asrequired for secondary intergradation, it must have been relativelyrecent and of short duration. Herein we discuss the roles ofgenetic drift, random migration, nonrandom migration, selectionand others as potential driving forces for both modes of clineformation. In addition, we address the potential role of thelast glacial period in (1) creating isolating barriers, (2)the opening of unoccupied habitats for range extension, and(3) as a mechanism for thermal selection. While some evidenceexists that at least one of the driving forces is selection,the extent to which it and other deterministic forces participateas opposed to various stochastic processes must await furtheranalysis     

Involvement of Hormonal Balance in the Control of the 'Bullhead' Malformation in Baccara Rose Flowers

Gibberellin activity is much lower and cytokinin activity ishigher in the flowers of roses grown at a relatively low temperatureand in ‘pbullhead’ malformed flowers which appearin such conditions, compared to ‘normal’ flowersgrown at higher temperatures. Injection of gibberellin intothe receptacle of flowers grown at low temperature preventsthe symptoms of malformation. Injection with cytokinin of thoseflowers had no effect, but addition of BA¹ to GA injection abolishesthe malformation-preventing effect of the gibberellin. Cytokinintreatment of plants grown at higher temperatures causes proliferationof the nectary and promotes appearance of adventitious floretswhich are characteristic symptoms of malformed flowers. The level of auxin is higher in higher temperatures, but therewas no effect on the development of flowers at the various temperaturesby applying auxin. The involvement of hormonal balance in theabnormal development of rose flowers is discussed.     

The Anther Smut of Sea Campion: A Study of the Role of Growth Regulators in the Dwarfing Symptom

The sympton of dwarfing in the sea campion, Silene vulgaris(Moench) Garcke sub sp. maritima(With.) A. & D. Löveinfected with the anther smut fungus Ustilago violacea (Pers.)Fuckel, a systemic, perennial parasite, has been investigated. Extracts of both healthy and diseased plants contain IAA andGA₃, but diseased plants contain less gibberellins than healthyplants. Neither IAA nor gibberellins were detected in significantquantities in the medium when U. violacea was grown in pureculture, but IAN was present. IAN was also found m extractsof diseased plants and it is tentatively suggested that it isformed by the fungus and may accumulate in the host owing tothe inability of the plant to convert IAN to IAA The exogenousapplication of IAN to healthy plants does not produce any diseasesymptoms. The dwarfing symptom of the diseased plant may be due to thelower levels of gibberellins which it contains compared withhealthy plants since the exogenous application of GA₃, restoresthe diseased plant to normal growth     

Biologic,Immunocytochemical, and Cytogenetic Characterization of Two New Human Melanoma Cell Lines: IIB-MEL-LES and IIB-MEL-IAN

Two human melanoma cell lines, derived from metastases of two patients with epithelioid malignant amelanotic melanomas, and designated IIB-MEL-LES and IIB-MEL-IAN, have been established. Both cell lines have been in continuous culture over 2 years and were propagated continuously for 85 and 75 serial passages, respectively. Morphologically, IIB-MEL-LES is composed predominantly of spindle shaped cells, whereas IIB-MEL-IAN grows as a monolayer of cuboid and stellate shaped cells with many rounded cells in suspension. Immunocytochemical studies revealed that both cell lines express S-100 protein, vimentin, and GD₃ and GD₂ gangliosides but are negative for keratin and collagen. Both cell lines express HLA class I and HLA-DR antigens in variable proportions. The MAGE-1 gene is expressed only by the IIB-MEL-IAN cell line, as revealed by PCR analysis. Cytogenetic analysis of both cell lines revealed abnormal karyotypes; the modal chromosome numbers of IIB-MEL-LES and IIB-MEL-IAN were 48 and 81, respectively. IIB-MEL-LES cells presented rearrangements in chromosomes 1, 14 and X, gains in chromosomes 10,20, and 21 losses in chromosomes 15 and Y. The most frequent markers observed in IIB-MEL-IAN cells were 7q+, 10p+, 2p+, i(6p), 2q+, and 10q-. Clonal gains were observed in chromosomes 12 and 21, whereas losses were seen in chromosomes 1, 2, 3, 4, 6, 7, 11, and 17. Both cell lines were capable of forming colonies in soft agar and developed tumors when transplanted into nude mice, reproducing and maintaining the characteristics of the original tumors. These cell lines and their xenografts appear to provide useful systems for studying the biology, genetics and histogenesis of human malignant melanoma and could be utilized for the development of melanoma vaccines.     

Cytology of Encephalartos hildebrandtii A. Br. & Bouche

The chromosomes of Encephalartos hildebrandtii A. Br. &Bouche were studied from root tip cells (2n–27), and theplant was found to be a triploid on the basic chromosome number9. Karyotype analysis has shown that the somatic complementconsists of two sets of chromosomes, a diploid set of 18 chromosomesin nine paris, and a haploid set of 9, and therefore it is suggestedthat this is an allotriploid. This is the first report of a polyploid species in the genusEncephalartos, and also in the whole of the Cycadales.     

Changing land use reduces soil CH4 uptake by altering biomass and activity but not composition of high-affinity methanotrophs

Forest ecosystems assimilate more CO₂ from the atmosphere and store more carbon in woody biomass than most nonforest ecosystems, indicating strong potential for afforestation to serve as a carbon management tool. However, converting grasslands to forests could affect ecosystem–atmosphere exchanges of other greenhouse gases, such as nitrous oxide and methane (CH₄), effects that are rarely considered. Here, we show that afforestation on a well-aerated grassland in Siberia reduces soil CH₄ uptake by a factor of 3 after 35 years of tree growth. The decline in CH₄ oxidation was observed both in the field and in laboratory incubation studies under controlled environmental conditions, suggesting that not only physical but also biological factors are responsible for the observed effect. Using incubation experiments with ¹³CH₄ and tracking ¹³C incorporation into bacterial phospholipid fatty acid (PLFA), we found that, at low CH₄ concentrations, most of the ¹³C was incorporated into only two PLFAs, 18 : 1ω7 and 16 : 0. High CH₄ concentration increased total ¹³C incorporation and the number of PLFA peaks that became labeled, suggesting that the microbial assemblage oxidizing CH₄ shifts with ambient CH₄ concentration. Forests and grasslands exhibited similar labeling profiles for the high-affinity methanotrophs, suggesting that largely the same general groups of methanotrophs were active in both ecosystems. Both PLFA concentration and labeling patterns indicate a threefold decline in the biomass of active methanotrophs due to afforestation, but little change in the methanotroph community. Because the grassland consumed CH₄ at a rate five times higher than forest soils under laboratory conditions, we concluded that not only biomass but also cell-specific activity was higher in grassland than in afforested plots. While the decline in biomass of active methanotrophs can be explained by site preparation (plowing), inorganic N (especially NH₄⁺) could be responsible for the change in cell-specific activity. Overall, the negative effect of afforestation of upland grassland on soil CH₄ uptake can be largely explained by the reduction in biomass and to a lesser extent by reduced cell-specific activity of CH₄-oxidizing bacteria.