scholarly journals R-STIPPLED MAIZE AS A TRANSPOSABLE ELEMENT SYSTEM

Genetics ◽  
1984 ◽  
Vol 107 (3) ◽  
pp. 477-488
Author(s):  
W M Williams ◽  
K V Satyanarayana ◽  
J L Kermicle
Keyword(s):  
Transposable Element ◽  
Pollen Grains ◽  
Linkage Phase ◽  
Element System ◽  
In Trans ◽  
A Site

ABSTRACT The I-R element at the R locus destabilizes kernel pigmentation giving the variegated pattern known as stippled (R-st). In trans linkage phase with R-st the element was shown to act as a modifier of stippled, intensifying seed spotting in parallel with effects of the dominant linked modifier M-st. Presence of I-R in the genome was, therefore, shown to be detectable as a modifier of R-st. When this test was used, new modifiers resembling M-st were often detected following mutations of R-st to the stable allele R-sc. Such mutations evidently occurred by transposition of I-R away from the R locus to a site where it was identifiable as a modifier. M-st may be such a transposed I-R. Analysis of mutations to R-sc during the second (sperm-forming) mitosis in pollen grains showed that some of the transposed I-R elements were linked with R, whereas others assorted independently. Their strengths varied from barely discernible to a level equal to M-st. Overreplication frequently accompanied transposition at the sperm-forming mitosis, leading to transposed I-R elements in both the mutant and nonmutant sperm.

scholarly journals piRNA Clusters Need a Minimum Size to Control Transposable Element Invasions

2020 ◽  
Vol 12 (5) ◽  
pp. 736-749 ◽  
Author(s):  
Robert Kofler
Keyword(s):  
Population Genetics ◽  
Transposable Element ◽  
Minimum Size ◽  
Total Size ◽  
Evolutionary Forces ◽  
A Genome ◽  
In Trans ◽  
Single Insertion

Abstract piRNA clusters are thought to repress transposable element (TE) activity in mammals and invertebrates. Here, we show that a simple population genetics model reveals a constraint on the size of piRNA clusters: The total size of the piRNA clusters of an organism must exceed 0.2% of a genome to repress TE invasions. Moreover, larger piRNA clusters accounting for up to 3% of the genome may be necessary when populations are small, transposition rates are high, and TE insertions are recessive. If piRNA clusters are too small, the load of deleterious TE insertions that accumulate during a TE invasion may drive populations extinct before an effective piRNA-based defense against the TE can be established. Our findings are solely based on three well-supported assumptions: 1) TEs multiply within genomes, 2) TEs are mostly deleterious, and 3) piRNA clusters act as transposon traps, where a single insertion in a cluster silences all TE copies in trans. Interestingly, the piRNA clusters of some species meet our observed minimum size requirements, whereas the clusters of other species do not. Species with small piRNA clusters, such as humans and mice, may experience severe fitness reductions during invasions of novel TEs, which is possibly even threatening the persistence of some populations. This work also raises the important question of how piRNA clusters evolve. We propose that the size of piRNA clusters may be at an equilibrium between evolutionary forces that act to expand and contract piRNA clusters.

Genetic and molecular analysis of the Enhancer (En) transposable element system of Zea mays

1985 ◽  
Vol 4 (1) ◽  
pp. 17-23 ◽  
Author(s):  
Andy Pereira ◽  
Zsuzsanna Schwarz-Sommer ◽  
Alfons Gierl ◽  
Isolde Bertram ◽  
Peter A. Peterson ◽  
...  
Keyword(s):  
Zea Mays ◽  
Transposable Element ◽  
Molecular Analysis ◽  
Element System

Effects of dopamine blockade on renal sodium excretion

1983 ◽  
Vol 245 (2) ◽  
pp. F247-F253 ◽  
Author(s):  
J. C. Pelayo ◽  
R. D. Fildes ◽  
G. M. Eisner ◽  
P. A. Jose
Keyword(s):  
Sodium Excretion ◽  
Dopamine Antagonist ◽  
Single Nephron ◽  
Proximal Tubular ◽  
In Trans ◽  
Series Of Experiments ◽  
Tubular Flow ◽  
Excretion Rates ◽  
A Site ◽  
Renal Responses

The renal responses to a specific dopamine antagonist (cis-flupentixol) and its stereoisomer (trans-flupentixol), a weak dopamine antagonist, were examined during hydropenia and Ringer loading in anesthetized rats. During hydropenia glomerular filtration (GFR), absolute (UNaV), and fractional (FENa) sodium excretion rates were similar as were single-nephron filtration (SNGFR) and proximal tubular flow rate (VTF). After Ringer loading GFR, UNaV, and FENa increased in all groups, but the increments were less in the cis-flupentixol than in the control or trans-flupentixol group. SNGFR and VTF increased similarly in all groups. In another series of experiments Ringer loading was performed prior to drug administration. Perfusion pressure (PP) was decreased in trans-flupentixol rats by aortic constriction to control for cis-flupentixol-induced reduction in PP. UNAV and FENa were lower in the cis-flupentixol- than trans-flupentixol-treated rats at comparable PP and GFR. In conclusion, dopamine blockade attenuated the natriuresis of Ringer loading; the mechanism is uncertain but may be related to a tubular effect at a site beyond the proximal convoluted tubule and/or in deeper nephrons.

scholarly journals The Hermes transposable element from the house fly, Musca domestica, is a short inverted repeat-type element of the hobo, Ac, and Tam3 (hAT) element family

1994 ◽  
Vol 64 (2) ◽  
pp. 87-97 ◽  
Author(s):  
William D. Warren ◽  
Peter W. Atkinson ◽  
David A. O'Brochta
Keyword(s):  
Zea Mays ◽  
Transposable Element ◽  
Musca Domestica ◽  
House Fly ◽  
Inverse Pcr ◽  
Sequence Motif ◽  
Terminal Sequence ◽  
Repeat Type ◽  
Genetic Tool ◽  
Element System

SummaryThe genome of the house fly, Musca domestica, contains an active transposable element system, called Hermes. Using PCR and inverse PCR we amplified and sequenced overlapping segments of several Hermes elements and from these data we have constructed a 2749 bp consensus Hermes DNA sequence. Hermes termini are composed of 17 bp imperfect inverted repeats that are almost identical to the inverted terminal repeats of the hobo element of Drosophila melanogaster. Full length Hermes elements contain a single long ORF capable of encoding a protein of 612 amino acids which is 55% identical to the amino acid sequence of the hobo transposase. Comparison of the ends of the Hermes and hobo elements to those of the Ac element of Zea mays, and the Tam3 element of Antirrhinum majus, as well as several other plant and insect elements, revealed a conserved terminal sequence motif. Thus Hermes is clearly a member of the hobo, Ac and Tam3 (hAT) transposable element family, other members of which include the Tagl element from Arabidopsis thaliana and the Bg element from Zea mays. The evolution of this class of transposable elements and the potential utility of Hermes as a genetic tool in M. domestica and related species are discussed.

scholarly journals Are Reproductive Traits Related to Pollen Limitation in Plants? A Case Study from a Central European Meadow

Plants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 640
Author(s):  
Michael Bartoš ◽  
Štěpán Janeček ◽  
Petra Janečková ◽  
Eliška Chmelová ◽  
Robert Tropek ◽  
...  
Keyword(s):  
Pollen Limitation ◽  
Abiotic Factors ◽  
Pollen Grains ◽  
Reproductive Traits ◽  
Biodiversity Loss ◽  
Plant Reproduction ◽  
Landscape Fragmentation ◽  
Global Changes ◽  
A Site ◽  
Relationship Of

The deficiency of pollen grains for ovule fertilization can be the main factor limiting plant reproduction and fitness. Because of the ongoing global changes, such as biodiversity loss and landscape fragmentation, a better knowledge of the prevalence and predictability of pollen limitation is challenging within current ecological research. In our study we used pollen supplementation to evaluate pollen limitation (at the level of seed number and weight) in 22 plant species growing in a wet semi-natural meadow. We investigated the correlation between the pollen limitation index (PL) and floral traits associated with plant reproduction or pollinator foraging behavior. We recorded significant pollen limitation for approximately 41% of species (9 out of 22 surveyed). Seven species had a significant positive response in seed production and two species increased in seed weight after pollen supplementation. Considering traits, PL significantly decreased with the number of pollinator functional groups. The relationship of PL with other examined traits was not supported by our results. The causes of pollen limitation may vary among species with regard to (1) different reproductive strategies and life history, and/or (2) temporary changes in influence of biotic and abiotic factors at a site.

scholarly journals piRNA clusters need a minimum size to control transposable element invasions

2019 ◽  
Author(s):  
Robert Kofler
Keyword(s):  
Population Genetics ◽  
Transposable Element ◽  
Minimum Size ◽  
Total Size ◽  
Evolutionary Forces ◽  
A Genome ◽  
In Trans ◽  
Element Activity ◽  
Single Insertion

AbstractpiRNA clusters are thought to repress transposable element activity in mammals and invertebrates. Here we show that a simple population genetics model reveals a constraint on the size of piRNA clusters: the total size of the piRNA clusters of an organism ought to exceed 0.2% of a genome. Larger piRNA clusters accounting for up to 3% of the genome may be necessary when populations are small, transposition rates are high and TE insertions recessive. If piRNA clusters are too small the load of deleterious TE insertions accumulating during a TE invasion may drive populations extinct before an effective piRNA based defence against the TE can be established. Our finding is solely based on three well supported assumptions: i) TEs multiply withing genomes, ii) TEs are mostly deleterious and iii) piRNA clusters act as transposons traps, where a single insertion in a cluster silences all TE copies in trans. Interestingly, piRNA clusters of some species meet our minimum size requirements while clusters of other species don’t. Species with small piRNA clusters, such as humans and mice, may experience severe fitness reductions during invasions of novel TEs, possibly even threatening the persistence of some populations. This work also raises the important question of how piRNA clusters evolve. We propose that the size of piRNA clusters may be at an equilibrium between evolutionary forces that act to expand and contract piRNA clusters.

scholarly journals Ac induces homologous recombination at the maize P locus.

Genetics ◽  
1991 ◽  
Vol 128 (1) ◽  
pp. 163-173 ◽  
Author(s):  
P Athma ◽  
T Peterson
Keyword(s):  
Homologous Recombination ◽  
Transposable Element ◽  
Direct Repeat ◽  
Null Alleles ◽  
Direct Repeats ◽  
Ac Element ◽  
Repeat Sequences ◽  
P Gene ◽  
In Trans ◽  
P Locus

Abstract The maize P gene conditions red phlobaphene pigmentation to the pericarp and cob. Starting from two unstable P alleles which carry insertions of the transposable element Ac, we have derived 51 P null alleles; 47 of the 51 null alleles have a 17-kb deletion which removes the 4.5-kb Ac element and 12.5 kb of P sequences flanking both sides of Ac. The deletion endpoints lie within two 5.2-kb homologous direct repeats which flank the P gene. A P allele which contains the direct repeats, but does not have an Ac insertion between the direct repeats, shows very little sporophytic or gametophytic instability. The apparent frequency of sporophytic mutations was not increased when Ac was introduced in trans. Southern analysis of DNA prepared from the pericarp tissue demonstrates that the deletions can occur premeiotically, in the somatic cells during development of the pericarp. Evidence is presented that the deletions occurred by homologous recombination between the two direct repeats, and that the presence of an Ac element at the P locus is associated with the recombination/deletion. These results add another aspect to the spectrum of activities of Ac: the destabilization of flanking direct repeat sequences.

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