Genetic and morphological divergence between populations of the flatfish Platichthys flesus (L.) (Pleuronectidae)

Populations of the flounder, Platichthys flesus , were screened for electrophoretically detectable protein variation at up to 37 loci. Atlantic and North Sea populations (subspecies flesus ) were genetically very similar to one another ( I >0.99) but different from Adriatic (subspecies italicus ) and Black Sea (subspecies luscus ) populations. The values for genetic identity between subspecies were around 0.9. Diagnostic loci enabled specimens of flesus, italicus and luscus to be differentiated from one another. Samples of flesus showed two to three times the heterozygosity levels of italicus or luscus , consistent with the greater population size of flesus . Morphological comparisons enabled populations to be categorized to subspecies. Platichthys flesus italicus and luscus are valid subspecies: the terms are not synonyms. The genetic distance data provide an estimate of divergence time of the three subspecies at about 2 My ago, an estimate that seems reasonable in the light of present knowledge concerning the recent geological histories of the Mediterranean and Black Sea basins.     

Early stomatal closure in waterlogged pea plants is mediated by abscisic acid in the absence of foliar water deficits

Abstract Soil waterlogging decreased leaf conductance (interpreted as stomatal closure) of vegetative pea plants (Pisuin sativum L. cv. ‘Sprite’) approximately 24 h after the start of flooding, i.e. from the beginning of the second 16 h-long photo-period. Both adaxial and abaxial surfaces of leaves of various ages and the stipules were affected. Stomatal closure was sustained for at least 3 d with no decrease in foliar hydration measured as water content per unit area, leaf water potential or leaf water saturation deficit. Instead, leaves became increasingly hydrated in association with slower transpiration. These changes in the waterlogged plants over 3 d were accompanied by up to 10-fold increases in the concentration of endogenous abscisic acid (ABA). Waterlogging also increased foliar hydration and ABA concentrations in the dark. Leaves detached from non-waterlogged plants and maintained in vials of water for up to 3 d behaved in a similar way to leaves on flooded plants, i.e. stomata closed in the absence of a water deficit but in association with increased ABA content. Applying ABA through the transpiration stream to freshly detached leaflets partially closed stomata within 15 min. The extractable concentrations of ABA associated with this closure were similar to those found in flooded plants. When an ABA-deficient ‘wilty’ mutant of pea was waterlogged, the extent of stomatal closure was less pronounced than that in ordinary non-mutant plants, and the associated increase in foliar ABA was correspondingly smaller. Similarly, waterlogging closed stomata of tomato plants within 24 h, but no such closure was seen in ‘flacca’, a corresponding ABA-deficient mutant. The results provide an example of stomatal closure brought about by stress in the root environment in the absence of water deficiency. The correlative factor operating between the roots and shoots appeared to be an inhibition of ABA transport out of the shoots of flooded plants, causing the hormone to accumulate in the leaves.     

Hormone directed sucrose transport during fruit set induced by gibberellins in Pisum sativum

A new system has been developed to study hormone-directed transport in intact plants during parthenocarpic fruit set induced by gibberellins. Gibberellic acid (GA₃) and gibberellin A₁ (GA₁) applied to unpollinated ovaries of pea ( Pisum sativum L. cv. Alaska) promoted sucrose transport from the leaf to the site of hormone application. In vivo experiments showed an early (30 min) accumulation of [¹⁴C]-sucrose in ovaries of pea stimulated by gibberellins. This activation of sucrose transport appears to be mediated by gibberellins (GA₁, GA₃), increasing both loading of phloem with sucrose in the leaf (source) and sucrose unloading in the ovary (sink). The ability of pea tissue segments to take up sucrose in vitro was not affected by the hormonal treatment.     

The genetic relationships between the kringle domains of human plasminogen,prothrombin, tissue plasminogen activator,urokinase, and coagulation factor XII

Summary A computer-based statistical evaluation of the optimal alignments of the kringle domains of human plasminogen, human prothrombin, human tissue plasminogen activator, human urokinase, and human coagulation Factor XIIa, as well as the putative kringle of human haptoglobin, has been performed. A variety of different alignments has been examined and scores calculated in terms of the number of standard deviations (SD) of a given match from randomness. With the exception of human haptoglobin, it was found that very high alignment scores (8.9–23.0 SD from randomness) were obtained between each of the kringles, with the kringle 1 and kringle 5 regions of human plasminogen displaying the highest similarity, and the S kringle of human prothrombin and the human Factor XII kringle showing the least similarity. The relationships obtained were employed to construct an evolutionary tree for the kringles. The predicted alignments have also allowed nucleotide mutations in these regions to be evaluated more accurately. For those regions for which nucleotide sequences are known, we have employed the maximal alignments from the protein sequences to assess nucleotide sequence similarities. It was found that a range of approximately 40–55% of the nucleotide bases were placed at identical positions in the kringles, with the highest number found in the alignment of the two kringles of human tissue plasminogen activator and the lowest number in the alignment of the S kringle of prothrombin with the second kringle of tissue plasminogen activator. From both protein and nucleotide alignments, we conclude that haptoglobin is not statistically homologous to any other kringle.Secondary structural comparisons of the kringle regions have been predicted by a combination of the Burgess and Chou-Fasman methods. In general, the kringles display a very high number of -turns, and very low -helical contents. From analysis of the predicted structures in relationship to the functional properties of these domains, it appears as though many of their functional differences can be related to possible conformational alterations resulting from amino acid substitutions in the kringles.     

Experimental evidence on the affinities ofPapaver somniferum (Papaveraceae)

Results obtained from crossing experiments betweenP. somniferum subsp.somniferum (2n = 22) and subsp.setigerum (2n = 44),P. glaucum (2n = 14) andP. gracile (2n = 14) and from the observation of meiotic chromosome pairing in the various hybrids obtained do not provide straightforward evidence for the hypothesis thatP. somniferum originated as a triploid hybrid between taxa similar toP. glaucum andP. gracile (Kadereit 1986a, b).—On the one hand, the pattern of crossability found reflects the closer similarity of subsp.somniferum toP. glaucum and of subsp.setigerum toP. gracile, which was interpreted as segregation of parental characters, and the high frequency of 2n = 28 chromosomes among F₂-progeny from the hybrid subsp.somniferum × subsp.setigerum (2n = 33) might reveal n = 7 as the base number also ofP. somniferum. On the other hand, however, the general difficulty of obtaining hybrids, and the low incidence of bivalent formation in their meiosis, probably indicating a lack of chromosome homology between the different species, do not fit the above hypothesis.—These results are in marked contrast to the morphological similarity between the three species involved.     

Age,growth and reproductive biology of the silky shark,Carcharhinus falciformis,and the scalloped hammerhead,Sphyrna lewini,from the northwestern Gulf of Mexico

Synopsis The silky shark, Carcharhinus falciformis, and scalloped hammerhead, Sphyrna lewini, represent >80% of the shark by-catch of the winter swordfish/tuna longline fishery of the northwestern Gulf of Mexico. This catch represents a potential supplemental fishery, yet little is known of the life histories of the two species. This report relates reproductive biology data to age and growth estimates for 135 C. falciformis and 78 S. lewini. Unlike other regional populations, C. falciformis in the Gulf of Mexico may have a seasonal 12 month gestation period. Males mature at 210–220 cm TL (6–7 yr); females at >225 cm TL (7–9 yr). Application of age at length data for combined sexes produced von Bertalanffy growth model parameter estimates of L_∞ = 291 cm TL, K = 0.153, t₀ = −2.2 yr. Adult male S. lewini outnumbered adult females in catches because of differences in the distributions of the sexually segregated population. Males mature at 180 cm TL (10 yr); females at 250 cm TL (15 yr). von Bertalanffy parameter estimates for combined sexes of this species were L_∞ = 329 cm TL, K = 0.073, t_o = −2.2 yr.     

Phylogenetic systematics of the nymphaeales

A cladistic analysis was applied to reveal the phylogenetic relationships among the Nymphaeales. Seventeen out of twenty three characters in gross morphology, anatomy and palynology were analyzed, for their evolutionary polarities. From the results of the present analysis, the phylogenetic status of each genus and their relationships were clarified: 1)Nelumbo is a distinct taxon and is presumed to have originated from an ancestral stock of the Nymphaeales; 2)Ceratophyllum has a close phylogenetic relationship withCabomba; and 3) in the Nymphaeaceaesensu stricto, Nuphar and the remaining genral constitute a monophyletic group. A conclusion obtained from the present analysis was that the following three families should be recognized in the Nymphaeales; Nelumbonaceae Nymphaeaceae, and Ceratophyllaceae. The generaBrasenia andCabomba are traditionally classified in the Nymphaeaceae or in the independent family Cabombaceae. However, they should be included in the family Ceratophyllaceae.     

Evolutionary relationship between Enterobacteriaceae: comparison of the ATP synthases (F1F0) of Escherichia coli and Klebsiella pneumoniae

The ATP synthase complex of Klebsiella pneumoniae (KF₁F₀) has been purified and characterized. SDS-gel electrophoresis of the purified F₁F₀ complexes revealed an identical subunit pattern for E. coli (EF₁F₀) and K. pneumoniae. Antibodies raised against EF₁ complex and purified EF₀ subunits recognized the corresponding polypeptides of EF₁F₀ and KF₁F₀ in immunoblot analysis. Protease digestion of the individual subunits generated an identical cleavage pattern for subunits , , , , a, and c of both enzymes. Only for subunit different cleavage products were obtained. The isolated subunit c of both organisms showed only a slight deviation in the amino acid composition. These data suggest that extensive homologies exist in primary and secondary structure of both ATP synthase complexes reflecting a close phylogenetic relationship between the two enterobacteric tribes.Abbreviations ACMA 9-amino-6-chloro-2-methoxyacridine - DCCD N,N-dicyclohexylcarbodiimide - FITC fluorescein isothiocyanate - SDS sodium dodecyl sulfate - TTFB 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole     

Genetic variation and distances of five Italian native sheep breeds

Genetic distances among five of the most important Italian native sheep breeds were estimated by using gene frequencies of four blood group and seven blood protein loci and by three different computing methods. The values of the three distance matrices were highly correlated. Genetic distances were found within the range values reported in the literature for local breeds. Shorter distances fitted the historical evidence of migrations.