The DNA sequnce of the transposable element Ac of Zea mays L.

Summary The sequence of the Ac element isolated from the wx-m7 allele has been determined. The Ac element is 4563 bp long. A central portion of roughly 3.1 kb is occupied by three open reading frames, two of which point in one direction and the third in the opposite direction. One of the reading frames potentially encodes a protein with a ten-fold repeat of pro gluN and pro glu dipeptides near its N-terminus. The sequences outside the open reading frames are characterized by the presence of a number of direct and inverted repeats. The Ac element may thus have evolved from a simpler progenitor structure. The sequence we have determined for the Ac from the wx-m7 allele differs in a few key positions from that reported for the Ac element from the wx-m9 allele (Pohlman et al. 1984). We have resequenced these positions in both Ac elements and find them to be identical. We conclude that the phenotypic differences between the two waxy alleles are not caused by structural differences in the Ac elements but rather may be attributable to the differences in their insertion sites.     

Cross-linking a maturation-dependent ram sperm plasma membrane antigen induces the acrosome reaction

ESA152 is a highly hydrophobic 18 kDa sialoglycoprotein, which becomes expressed on ram sperm in the proximal cauda epididymis. ESA 152 is expressed on all regions of the sperm surface, most strongly on the posterior region of the head, most weakly on the anterior region of the head. In this paper, we show that induction of the acrosome reaction with Ca2+ ionophore causes ESA152 to be redistributed from the posterior to the anterior region of the head plasma membrane. Cross-linking ESA152 with bivalent antibody causes similar redistribution and induces the acrosome reaction. Induction of the acrosome reaction with ESA152 antibody requires Ca2+ but is insensitive to (10 ng/ml) pertussis toxin.     

Immunochemical analysis of parasporal crystal digests of Bacillus thuringiensis as an index of insecticidal activity

An immunoelectrophoretic method is described for analyzing alkali parasporal crystal digests of Bacillus thuringiensis preparations (Dipel^TM). There were two distinct immunoprecipitate peaks (A and B) in the direction of the anode. The higher A peak had no correlation with the bioactivity of B. thuringiensis samples, whereas, the height of the B peak was directly proportional to the bioactivity. There was excellent agreement between the immunoassay and the bioassay of insecticidal potency in terms of international units.     

Unbiased analyses of ITS folding motifs in a taxonomically confusing lineage: Anagnostidinema visiae sp. nov. (cyanobacteria)

Cyanobacteria are diverse prokaryotic, photosynthetic organisms present in nearly every known ecosystem. Recent investigations around the world have recovered vast amounts of novel biodiversity in seldom sampled habitats. One phylogenetically significant character, the secondary folding structures of the 16S–23S ITS rDNA region, has allowed an unprecedented capacity to erect new species. However, two questions arise: Is this feature as informative as is proposed, and how do we best employ these features? Submerged sinkholes with oxygen-poor, sulfur-rich ground water in Lake Huron (USA) contain microbial mats dominated by both oxygenic and anoxygenic cyanobacteria. We sought to document some of this unique cyanobacterial diversity. Using culture-based investigations, we recovered 45 strains, of which 23 were analyzed employing 16S–23S rDNA sequences, ITS folding patterns, ecology, and morphology. With scant morphological discontinuities and nebulous 16S rDNA gene sequence divergence, ITS folding patterns were effective at articulating cryptic biodiversity. However, we would have missed these features had we not folded all the available motifs from the strains, including those with highly similar 16S rDNA gene sequences. If we had relied solely on morphological or 16S rDNA gene data, then we might well have missed the diversity of Anagnostidinema. Thus, in order to avoid conformation basis, which is potentially common when employing ITS structures, we advocate clustering strains based on ITS rDNA region patterns independently and comparing them back to 16S rDNA gene phylogenies. Using a total evidence approach, we erected a new taxon according to the International Code of Nomenclature for Algae, Fungi, and Plants: Anagnostidinema visiae.     

Conformational study of linear alternating and mixed D- and L-proline oligomers using electronic and vibrational CD and fourier transform IR

Vibrational CD (VCD) spectra of a series of blocked linear, alternating D - and L -proline containing oligopeptides, dissolved in D₂O and in CDCl₃. are reported. For the Boc-LDL -Pro₃ to Boc-DLDLDLDL-Pro₈ oligomers. The VCD spectra in the amide I band is a positive couplet, opposite in sense to that obtained for (L -Pro)_n oligomers. While this admits the possibility of their favoring a right-handed helical chain conformation, the amide I ir spectra for these dl oligomers in D₂O indicate a mixed, apparently alternate, cis-trans conformation that prevents a simple conclusion. Their VCD in D₂O evidence no narrowing and has a progressive loss in intensity (measured as Δ /A,) with an increase in chain length. In CDCl₃a similar pattern of positive VCD couplets decreasing in intensity with length was seen, but their spectra are narrower. Their electronic CD (ECD) in the uv, also indicates a loss in intensity with increasing length. Oligomers with odd or even numbers of Pro residues have different ECD patterns, indicating that those spectra are strongly influenced by local contributions arising in the N-terminal groups. The VCD arises from dipolar and vibrational coupling of the amides in the helical structure. All the spectra are consistent with the chiral end groups leading to formation of an excess of one helical handedness. With an increase in length, the influence of this selectiveness is less and the overall CD measured decreases. © 1995 John Wiley & Sons, Inc.     

Ac-Induced Instability at the Xanthophyllic Locus of Tomato

To detect genomic instability caused by Ac elements in transgenic tomatoes, we used the incompletely dominant mutation Xanthophyllic-1 (Xa-1) as a whole plant marker gene. Xa-1 is located on chromosome 10 and in the heterozygote state causes leaves to be yellow. Transgenic Ac-containing tomato plants which differed in the location and number of their Ac elements were crossed to Xa-1 tester lines and F(1) progeny were scored for aberrant somatic sectoring. Of 800 test and control F(1) progeny screened, only four plants had aberrantly high levels of somatic sectors. Three of the plants had twin sectors consisting of green tissue adjacent to white tissue, and the other had twin sectors comprised of green tissue adjacent to tissue more yellow than the heterozygote background. Sectoring was inherited and the two sectoring phenotypes mapped to opposite homologs of chromosome 10; the green/yellow sectoring phenotype mapped in coupling to Xa-1 while the green/white sectoring phenotype mapped in repulsion. The two sectoring phenotypes cosegregated with different single, non-rearranged Acs, and loss of these Acs from the genome corresponded to the loss of sectoring. Sectoring was still observed after transposition of the Ac to a new site which indicated that sectoring was not limited to a single locus. In both sectored lines, meiotic recombination of the sectoring Ac to the opposite homolog caused the phenotype to switch between the green/yellow and the green/white phenotypes. Thus the two different sectoring phenotypes arose from the same Ac-induced mechanism; the phenotype depended on which chromosome 10 homolog the Ac was on. We believe that the twin sectors resulted from chromosome breakage mediated by a single intact, transposition-competent Ac element.     

Relative position of the cheirogaleidae in strepsirhine phylogeny: A comparison of morphological and molecular methods and results

An examination of previous morphological and molecular studies of strepsirhine systematics suggests a conflict between the two types of data. Cladistic analyses of morphological data have indicated that the Malagasy primate family Cheirogaleidae is the sister taxon of the Afro-Asian lorisiforms and that together, cheirogaleids and lorisiforms comprise a monophyletic clade that excludes the Malagasy lemuriforms. Molecular studies, on the other hand, have consistently found that cheirogaleids and lemuriforms together are monophyletic to the exclusion of lorisiforms. Both types of studies, however, have suffered from methodological weaknesses: the morphological studies looked at too few characters and the molecular studies looked at too few taxa. This study examines a large and diverse morphological data set as well as molecular data from a comprehensive sample of strepsirhine taxa. The data sets are considered independently and jointly. When they are analyzed independently, the morphological data give weak support, and the molecular data strong support, to the hypothesis of Malagasy primate monophyly. When the two data sets are combined in a single analysis, the results are decisive. The “total evidence” approach yields compelling support to the hypothesis that cheirogaleids and remaining Malagasy lemuriforms comprise a monophyletic assemblage that excludes lorisiforms. © 1994 Wiley-Liss, Inc.     

Differences in water relations among the citrus leafminer and two different populations of its parasitoid inhabiting the same apparent microhabitat

The water balance relationships of adult females and pupae of two populations (Australian and Taiwan) of the parasitic wasp Ageniaspis citricola, a biological control agent of the citrus leafminer Phyllocnistis citrella, were compared to determine whether habitat preferences might differ between them. No differences were detected between Australian and Taiwan strains of the wasp during the pupal stage, but adult females from the Australian strain had lower net water loss rates than the parasitoid adults from Taiwan. This implies a greater moisture requirement by adults of the Taiwan strain, which should be considered before they are released into a new environment in classical biological control programs.