Genome organization in dicots. II. Arabidopsis as a ’bridging species’ to resolve genome evolution events among legumes

Analysis of molecular linkage groups within the soybean (Glycine max L. Merr.) genome reveals many homologous regions, reflecting the ancient polyploidy of soybean. The fragmented arrangement of the duplicated regions suggests that extensive rearrangements, as well as additional duplications, have occurred since the initial polyploidization event. In this study we used comparisons between homoeologous regions in soybean, and the homologous regions in the related diploids Phaseolus vulgaris and Vigna radiata, to elucidate the evolutionary history of the three legume genomes. Our results show that there is not only conservation of large regions of the genomes but that these conserved linkage blocks are also represented twice in the soybean genome. To gain a better understanding of the process of genome evolution in dicots, molecular comparisons have been extended to another well-studied species, Arabidopsis thaliana. Interestingly, the conserved regions we identified in the legume species are also relatively conserved in Arabidopsis. Our results suggest that there is conservation of blocks of DNA between species as distantly related as legumes and brassicas, representing 90 million years of divergence. We also present evidence for an additional, presumably earlier, genome duplication in soybean. These duplicated regions were only recognized by using Arabidopsis as a ’bridging’ species in the genome comparisons. Received: 10 October 2000 / Accepted: 13 January 2001     

Semifree-ranging Tufted Capuchins (Cebus apella) Spontaneously Use Tools to Crack Open Nuts

Naturalistic studies on tool use by nonhuman primates have focused almost exclusively on Old World monkeys or hominoids. We studied the cracking of Syagrus nuts with the aid of stones by a group of semifree-ranging capuchins living in a reforested area (Tietê Ecological Park, São Paulo, Brazil). Our data are from direct observation and from mapping nut-cracking site utilization. All adults, subadults and juveniles (plus one infant) crack nuts, but individual differences in frequency and proficiency are marked. Juveniles do most of the nut-cracking, but adults are, on average, more efficient; the frequency of inept stone manipulation decreases with age. About 10% of the nut-cracking episodes were watched by other individuals—mostly infants and juveniles, suggesting a role for observational learning, even if restricted to stimulus enhancement.     

The onset of starch degradation during banana ripening is concomitant to changes in the content of free and conjugated forms of indole-3-acetic acid

Banana (Musa acuminata AAA cv. Nanicão) slices were infiltrated with mannitol (control) and mannitol plus indole-3-acetic acid (IAA); then, some important ripening parameters like starch degradation, synthesis of ethylene and respiration were monitored. The contents of free-IAA and conjugated forms of IAA (ester and amide) were analyzed, by GC-MS-SIM, throughout the ripening in both banana slices and whole bananas. The starch degradation of IAA-treated slices was delayed for several days, but there was no difference between control and IAA-treated slices in the ethylene and respiration profiles. On day zero after infiltration, free-IAA levels were 500-fold higher in IAA-treated slices than in the control slices, but within 72 hours they declined to values 15-fold higher than those in the control group, with concomitant increase in IAA-ester. Similar to the banana slices, the onset of starch degradation occurred in whole bananas only when the free-IAA concentration was about 4 ng/g FW. The results herein suggest that IAA levels play a role during banana ripening in events like starch degradation with the consequence of banana sweetening.     

Effect of preservatives on IgG aggregation, complement-activating effect and hypotensive activity of horse polyvalent antivenom used in snakebite envenomation.

Intravenous administration of antivenoms is associated with early adverse reactions in a number of cases, but the causes of this phenomenon are still unclear. The effect of preservatives (phenol and thimerosal) on IgG aggregate and dimer formation, in vitro complement-activating effect and hypotensive activity of a whole IgG horse liquid polyvalent antivenom, produced by caprylic acid fractionation, was assessed. These parameters were studied since they have been associated with the development of early adverse reactions to the administration of antivenoms and human immunoglobulins. After a three-year storage period at 4 degrees C, antivenoms with preservatives had an increased content of IgG aggregates and dimers when compared with antivenom devoid of phenol and thimerosal. These observations correlate with a slight increment in the turbidity of preservative-containing antivenoms. The three antivenoms studied (formulation: no preservatives; with phenol and thimerosal; with thimerosal alone) activated human complement in vitro, with only minor quantitative differences among them. When antivenoms were administered as a bolus intravenous injection in rats, a rapid and prominent hypotension of short duration was observed after injection of phenol-containing antivenom, whereas such an effect was absent in antivenom free of preservative and in the one containing only thimerosal. Bolus injection of saline solution with phenol resulted in a similar hypotension, indicating that the effect is due to phenol. However, when phenol-containing antivenom was diluted 1:5 with saline solution before infusion, as occurs in the clinical use of this product, no hypotension was observed. Our results stress the need to evaluate the effects of preservatives on the physicochemical and pharmacological characteristics of antivenoms.     

Climatic stress, food availability and human activity as determinants of endemism patterns in the Mediterranean region: the case of dung beetles (Coleoptera, Scarabaeoidea) in the Iberian Peninsula

Abstract. A study to assess the influence of abiotic (climatic conditions) and biotic factors (food resources, habitat preference and human activity) on endemism patterns of dung beetles in the Mediterranean region was conducted in the Iberian Peninsula and the Balearic Islands. The Thermicity Index (It), the Mediterraneity Index (Im3) and the Aridity Index (Ia) were used to assess the influence of abiotic factors. Relative rabbit density (DR), the proportion of landscape used historically for grazing by sheep and goats and the nature of the food resource were used to assess the influence of biotic factors. Relative endemism (EN) of dung beetle assemblages was positively and significantly related with all of the factors considered. However, the Aridity and Mediterraneity Indices are the best predictors of EN. The predicted endemism (EN = 0.017 Ia + 0.004 Im3 + 0.422) was highly positively and significantly related with the observed endemism. Dung beetle assemblages with the highest relative endemism were observed in the south-eastern part of the Iberian Peninsula. This distribution corresponded to the highest Aridity and Mediterraneity. In contrast, dung beetle assemblages with lower endemism were located in more humid and temperate areas. Assemblages of dung beetles with the highest endemism comprise many species adapted to aridity and the exploitation of dry dung pellets. Conservation of traditional grazing activity by pellet-dropping sheep and goats might benefit the maintenance of dung beetle biodiversity in Mediterranean ecosystems.     

Asymmetry of Leg Use During Prey Handling in the Spider Scytodes globula (Scytodidae)

In spitting spiders Scytodes globula collected in the field, anterior leg loss was more frequent on the left than on the right side, possibly as an outcome of predatory episodes. A laboratory study was performed in which intact adult females of S. globula were placed with individuals from three species of recluse spiders, Loxosceles intermedia, L. gaucho, and L. laeta. The frequency of probing touches by spitting spiders to their prey was significantly higher with left leg I than with right leg I. Left leg II and right leg II also differed in touching frequency, but in a less marked way. The results, which may represent the first evidence of behavioral laterality in a spider species, suggest that behavioral asymmetry may be an ancient evolutionary trait.     

Functional characterization of an ammonium transporter gene from Lotus japonicus

NH₄⁺ is the main product of symbiotic nitrogen fixation and the external concentration of combined nitrogen plays a key regulatory role in all the different step of plant-rhizobia interaction. We report the cloning and characterization of the first member of the ammonium transporter family, LjAMT1;1 from a leguminous plant, Lotus japonicus. Sequence analysis reveals a close relationship to plant transporters of the AMT1 family. The wild type and two mutated versions of LjAMT1;1 were expressed and functionally characterized in yeast. LjAMT1;1 is transcribed in roots, leaves and nodules of L. japonicus plants grown under low nitrogen conditions, consistent with a role in uptake of NH₄⁺ by the plant cells.