bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deficiency analysis of female gametogenesis in maize
Authors: Vollbrecht Erik , Hake Sarah 
Published: May 2005

AbstractPlants produce female gametes through mitotic division in the multicellular, meioticolly reduced (haploid) megagametophyte phase. In flowering plants, the megagametophyte is the embryo sac; female gametogenesis or megagametogenesis comprises the ontogeny of the embryo sac. As a step toward understanding the role of embryo sac‐expressed genes in megagametogenesis, development of normal, haploid embryo sacs in maize was compared with development of embryo sacs deficient for various small, cytologically defined chromosomal regions. This analysis allowed us to screen 18% of the maize genome, including most of chromosome arms 1L and 3L, for phenotypes due specifically to deletion of essential, embryo sac‐expressed genes. Confocal laser scanning microscopy of whole developing embryo sacs confirmed that normal megagameto‐genesis in maize is of the highly stereotyped, bipolar Polygonum type common to most flowering plants examined to date. Deficiency embryo sac phenotypes were grouped into three classes, suggesting each deficient region contained one or more of at least three basic types of haploid‐expressed gene functions. In the first group, three chromosome regions contained genes required for progression beyond early, free‐nuclear stages of embryo sac development. Maintaining synchrony between events at the two poles of the embryo sac required genes located within two deficiencies. Finally, three chromosome regions harbored loci required for generation of normal cellular patterns typical of megagametogenesis. This analysis demonstrates that the embryo sac first requires postmeiotic gene expression at least as early as the first postmeiotic mitosis. Furthermore, our data show that a variety of distinct, genetically separable programs require embryo sac‐expressed gene products during megagametogenesis, and suggest the nature of some of those developmental mechanisms. © 1995 Wiley‐Liss, Inc.
Developmental and genetic mosaic analysis of Drosophila m‐dy mutants: Tissue foci for behavioral and morphogenetic defects
Authors: Newby Laurel M. , Jackson F. Rob 
Published: May 2005

AbstractMutants of the Drosophila miniature‐dusky (m‐dy) gene complex display morphogenetic phenotypes (miniature or dusky) caused by a change in the size and/or shape of the epidermal cells comprising the adult wing. In addition to a dusky phenotype, certain Andante‐type mutants also exhibit lengthened circadian periods for two different behavioral rhythms. If the latter phenotype results from a direct effect on the circadian pacemaker, the Andante function should be required within the brain. In order to define the tissues that require the morphogenetic and behavioral functions, we have carried out a genetic mosaic analysis. This study demonstrates that normal wing morphogenesis is entirely dependent on the genotype of wing cells. Furthermore, temperature‐shift experiments with a temperature‐sensitive dy mutant indicate that the morphogenetic function is required during adult development, and after the cessation of wing epidermal cell proliferation. At this time in development, a columnar epithelium in the developing wing becomes flattened into the mature wing blade, and we postulate that the cell‐size defect of m‐dy mutants results from an alteration of this mor‐phogenetic process. In contrast to the wing mor‐phogenesis phenotype, the characterization of locomotor activity in mosaic adults revealed a strong correlation between the head genotype and the Andante circadian‐period phenotype. This result indicates that neural tissues mediate the rhythm function. Thus, the behavioral and morphogenetic functions require gene expression in distinct tissues. Furthermore, the behavioral results are consistent with a requirement for Andante function within circadian pacemaker neurons. © 1995 Wiley‐Liss, Inc.
Biochemical analysis of programmed cell death during premeiotic stages of spermatogenesis in vivo and in vitro
Authors: Callard Gloria V. , Jorgensen Joan C. , Redding J. Michael 
Published: May 2005

AbstractControl points of regulator action during spermatogenesis are not completely known. Using the shark testis model, which facilitates analysis of spermatogenesis stage‐by‐stage in vivo and in vitro, an early biochemical marker of programmed cell death (PCD) was detected. Nucleosomal oligomers were seen in DNA extracts of testis and isolated spermatocysts (clonal germ cell/ Sertoli cell units) at premeiotic (PrM), but not meiotic (M) or postmeiotic (PoM), stages. Cell nuclei isolated from M stages of development were susceptible to cleavage by micrococcal nuclease, suggesting that developmental control of factors other than a nuclease‐insensitive chromatin structure may account for stage specificity. Cytological features of apoptosis were seen in germ cells, but not Sertoli cells, of a subset of isolated PrM spermatocysts and appeared to be all‐or‐none in affected clones. In culture, DNA fragmentation occurred on schedule with or without various additives, but the phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX) decreased accumulation of DNA breakdown products. Identification of the apoptotic form of PCD as a major, variable component of normal spermatogenesis and the use of PrM spermatocysts as an in vitro test system will allow further definition of mechanisms and developmental and physiological controls. © 1995 Wiley‐Liss, Inc.
Cell interactions in testis development: Overexpression of c‐mos in spermatocytes leads to increased germ cell proliferation
Authors: Higgy Nadia A. , Zackson Saul L. , Van Der Hoorn Frans A. 
Published: May 2005

AbstractPossible functions of the c‐mos proto‐oncogene during spermotogenesis were investigated through perturbations of its expression in transgenic mice. Two promoters, one from the pre‐meiotic male germ cell‐specific mouse phosphoglycerate kinase 2 gene, and the other from the post‐meiotic male germ cell‐specific rat RT7 gene were used to direct expression of c‐mos.Northern blot analysis of testis RNA from transgenic PGK‐c‐mos mice indicated elevated levels of c‐mos RNA in spermatocytes and spermatids compared to controls. No transgene expression was detected in any other tissue examined, suggesting that the mouse PGK2 promoter, like the previously used human PGK2 promoter, confers correct cell‐specific expression onto c‐mos.The promoter from a newly characterized rat gene, RT7, was shown to direct expression specific to post‐meiotic spermatids. Transgenic mice carrying an RT7‐lacZ construct displayed immunoreactive bacterial β‐galactosidase as well as enzyme activity in round spermatids. The cellular specificity for β‐galactosidase expression observed in RT7‐lacZ transgenic animals was in agreement with endogenous RT7 transcript expression. Northern blot analysis of testis RNA of RT7–c‐mos transgenic mice showed elevated levels of c‐mos in spermatids, but not in other cells or tissues examined.Western blot analysis demonstrated elevated levels of p43c‐mos in spermatids of both PGK–c‐mos and RT7–c‐mos transgenic animals, but only PGK–c‐mos transgenics had increased p43cc‐mos levels in spermatocytes. Both RT7–c‐mos and PGK–c‐mos transgenic mice are fertile and show no tendency toward transformation. RT7–c‐mos mice have no discernible phenotype associated with the c‐mos overexpression in spermatids. However, PGK–c‐mos transgenic males exhibited a significant increase in germ cell number, as determined by cell counts using total germ cells and germ cells fractionated by centrifugal elutriation. Because mitotic divisions of germ cells occur prior to PGK–c‐mos transgene expression, our observations suggest that c‐mos overexpression in spermatocytes causes an alteration in cell–cell interactions. © 1995 Wiley‐Liss, Inc.
Identification of two positive transcriptional elements within the 91‐base pair promoter for mouse testis angiotensin converting enzyme (testis ACE)
Authors: Zhou Yudong , Delafontaine Patrick , Martin Brian M. , Bernstein Kenneth E. 
Published: May 2005

AbstractTestis angiotensin‐converting enzyme (testis ACE) is an isozyme of ACE only expressed by male germ cells during spermiogenesis. It is the result of a strong sperm‐specific promoter found within the 12th intron of the somatic ACE gene. Previous studies have localized the boundaries of the mouse testis ACE promoter as being from −91 to −9, relative to the transcriptional start site, and have suggested two important DMA regulatory elements starting at positions −55 and −32. DNA constructs were made in which these motifs were either eliminated or substituted. Each construct was tested for its ability to promote transcription in vitro, using a rat testis nuclear extract. Disruption of either motif reduced in vitro transcription to about 30% of control levels, while mutations of both elements abolished transcription. Two sites were selected inside each motif and altered by point mutation. Each of four constructs, containing a mutation at −51, −48, −30, or −28, transcribed at 29% or less the efficiency of the parent construct. The DNA element at −55, TGAGGTCA, is homologous to a consensus cyclic AMP response element. The motif at −32, TCTTAT, is located at a position analogous to a TATA box. Substitution of the −32 motif with a consensus TATA box sequence, TATAAA, stimulated transcriptional activity about 3‐fold. As measured by gel mobility shift, oligonucleotides encompassing the −32 motif and the consensus TATA box formed different DNA‐protein complexes. However, the −32 motif oligonucleotide was recognized by nuclear proteins prepared from either liver or testis nuclei. In this example of a tissue‐specific promoter that functions only during spermatogenesis, at least two DNA elements act synergistically during in vitro transcription. © 1995 Wiley‐Liss, Inc.
Positive and negative feedback loops affect the transcription of IME1, a positive regulator of meiosis in Saccharomyces cerevisiae
Authors: Shefer‐Vaida Michal , Sherman Amir , Ashkenazi Tamar , Robzyk Kenneth , Kassir Yona 
Published: May 2005

AbstractThe IME1 gene of Saccharomyces cerevisiae encodes a transcription factor that is required for the expression of meiosis‐specific genes. Like many of the genes it regulates, IME1 itself is expressed according to the following complex pattern: barely detectable levels during vegetative growth, and high induced levels under starvation conditions, followed by a subsequent decline in the course of meiosis. This report examines the influence of Ime1 protein on its own expression, demonstrating feedback regulation. Disruption of either IME1 or IME2 leads to constantly increasing levels of Ime1‐lacZ expression, under meiotic conditions. This apparent negative regulation is due to cis elements in the IME1 upstream region, which confer transient meiotic expression to heterologous promoter‐less genes. A specific DNA/protein complex, whose level is transiently increased under meiotic conditions, is detected on this element. In ime1− diploids, the level of this DNA/protein complex increases, without any decline. These results indicate that the transient expression of IME1 is apparently due to transcriptional regulation. This report also presents evidence suggesting that Ime 1p is directly responsible for regulating its own transcription. Positive feedback regulation in mitotic conditions is suggested by the observation that overexpression of Ime 1p leads to increased levels of IME1‐lacZ. Negative autoregulation in meiotic cultures is demonstrated by the observation that a specific point mutation in IME1, ime 1–3, permits expression of meiosis‐specific genes, as well as induction of meiosis, but is defective in negative‐feedback regulation of IME1. © 1995 Wiley‐Liss, Inc.
Serum response element associated transcription factors in mouse embryos: Serum response factor, YY1, and PEA3 factor
Authors: Liu Shu‐Hui , Peng Bi‐Hung , Ma Jing‐Tyan , Liu Yin Chang , Ng Sun‐Yu 
Published: May 2005

AbstractMany mammalian transcription factors, including human and mouse serum response factors (SRFs), are post‐translationally modified with O‐linked N‐acetylglucosamine monosaccharides on multiple serine and/or threonine residues. Nuclear extracts were prepared from 9.5 to 19 days postcoitum mouse embryos and subsequently were fractionated by wheat germ agglutinin (WGA)‐agarose affinity chromatography. SRF binds WGA‐agarose and apparently is O‐glycosylated. On the other hand, the low molecular weight serum response element (SRE)‐binding proteins, including the previously named band I and band II factors, did not bind WGA‐agarose. Furthermore, we showed that the fastest migrating complex contains the Yin‐Yang 1 (YY1) factor. YY1 binds to the c‐fos SRE and skeletal β‐actin muscle regulatory element (MRE), but not the cardiac β‐actin MRE. Nuclear extracts from NIH/3T3 fibroblasts contain similar, if not identical, SRE‐binding complexes. Besides these SRE‐binding factors, mouse PEA3‐binding factor, presumably an ETS domain‐containing protein, was found to bind SRF protein. This physical interaction, between SRF and ETS domain proteins, was shown to involve the DNA‐binding domain‐containing region of SRF and not the carboxyl‐terminal transactivation domain. © 1995 Wiley‐Liss, Inc.
Developmental variability of metallothionein Mtn gene expression in the species of the Drosophila melanogaster subgroup
Authors: Bonneton François , Wegnez Maurice 
Published: May 2005

AbstractDevelopmental expression of the Drosophila melanogaster metallothionein Mtn gene has been analysed. Transcripts of this gene accumulate during the vitellogenic phase of oogenesis in a ring of follicular cells at the oocyte‐nurse cell margin and in the follicular cells surrounding the oocyte. There is also strong expression of the Mtn gene during the second half of embryogenesis in hemocytes, the endoderm midgut, and Malpighian tubules. A banded expression pattern is observed transiently in the midgut at stage 13. The two Mtn alleles, Mtn1 and Mtn.3, show quantitative differences in their expression patterns. Copper intoxication of flies does not induce ectopic expression of the Mtn gene, but rather leads to over‐expression of the gene in the structures where it is normally transcribed. Mtn transcription is not altered in homozygous mutants of four genes (lab, wg, dpp, bap) known to be involved in midgut morphogenesis.Expression of Mtn has been also studied in six other species of the melanogaster subgroup. This analysis demonstrates that regulation of Mtn gene transcription has changed during evolution of the Drosophila lineage. For example, Mtn is expressed specifically in the Malpighian tubules of D. melanogaster while in D. mauritiana and D. sechellia the amnioserosa is a specific location of expression. Nonetheless, expression of Mtn in the midgut is common to the seven species, suggesting a basic role for the MTN protein during embryogenesis in this organ, possibly in the release of metallic ions from vitellogenins. In contrast, two genes also expressed in the embryonic midgut, lab and dFRA display identical patterns in all species of the melanogaster subgroup. The diversity of Mtn patterns in closely related Drosophila species exemplifies the rapid evolution of a gene regulatory system. © 1995 Wiley‐Liss, Inc.
Genetic mosaic analysis of the equatorial‐less mutation in Drosophila mezunogaster
Authors: Fryxell Karl J. , Wood C. Paige 
Published: May 2005

Abstracteql (equatorial‐less) is a recessive lethal mutation on the second chromosome of Drosophila melanogasfer. J. Campos‐Ortega found that eql clones in somatic mosaic flies have reduced numbers of photoreceptor cells, and he suggested that only the R1, R6, and R7 photoreceptor cells were missing in this mutant. These photoreceptor cells help to define the inverted orientation of ommatidial facets along the equatorial midline of the fly eye, hence the mutation was named “equatorial‐less”. We have conducted a detailed analysis of the eql mutation, by serial section reconstruction of eql clones marked with bw or w− in somatic mosaic flies. We found that all photoreceptor cell types (Rl–R8) could be deleted by the eql mutation, and in rare cases the number of photoreceptor cells was increased. The apparent lack of photoreceptor cell type specificity was confirmed by our analysis of genetically mosaic facets, which indicated that no single photoreceptor cell, or subset of photoreceptor cells, was uniquely required to express eql Rather, eql appears to function in all photoreceptor cells, and possibly in all eye precursor cells. The distribution of photoreceptor cell numbers in w eql facets was consistent with the hypothesis that each photoreceptor cell was deleted independently of the others. The eql gene is located on the right arm of chromosome 2 at map location 2 − 104.5 ± 0.7 and lies between the polytene chromosome bands 59D8 and 60A7. © 1995 Wiley‐Liss, Inc.
Evaluation of an antisense RNA transgene for inhibiting growth hormone gene expression in transgenic rats
Authors: Matsumoto Kazuya , Kakidani Hitoshi , Anzai Masayuki , Nakagata Naomi , Takahashi Akio , Takahashi Yumi , Miyata Kenji 
Published: May 2005

AbstractWe compared the levels of growth hormone (GH) mRNA in the pituitary, plasma GH concentration, and altered phenotype in rats heterozygous and homozygous for an antisense RNA transgene targeted to the rat GH gene, with those in nontransgenic rats. We initially investigated whether the transgene promoter, which is connected to four copies of a thyroid hormone response element (TRE) that increases promoter activity, affected in vivo transgene expression in the pituitary of the transgenic rats. Plasma GH concentration correlated negatively with T, injection in surgically thyroidectomized heterozygous transgenic rats. There was a reduction of about ˜35–40% in GH mRNA levels in the pituitary of homozygous animals compared with those in non‐transgenic rats. Plasma GH concentration was significantly ˜25–32 and ˜29–41% lower in heterozygous and homozygous transgenic rats, respectively, compared with that in nontransgenic animals. Furthermore, the growth rates in homozygous transgenic rats were reduced by ˜72–81 and ˜51–70% compared with those of their heterozygous and nontransgenic littermates, respectively. The results of these studies suggested that the biological effect of GH in vivo is modulated dose‐dependently by the antisense RNA transgene. The rat GH gene can therefore be targeted by antisense RNA produced from a transgene, as reflected in the protein and RNA levels. © 1995 Wiley‐Liss, Inc.
Late embryo‐defective mutants of Arabidopsis
Authors: Vernon Daniel M. , Meinke David W. 
Published: May 2005

AbstractThe embryo‐defective (emb) mutants of Arabidopsis constitute a large and diverse group of mutants disrupted in a broad range of embryonic processes, including morphogonesis, cell differentiation, and maturation programs. This report describes a subset of these mutants, the late embryo defectives, which develop beyond the globular stage of embryogenesis but fail to complete normal morphogenesis. A representative sample of 12 late mutants was chosen for this study, patterns of morphogenesis were characterized, the germination potential of mutant seeds was investigated, and additional mutant alleles within the collection were identified. Morphological defects in mutant embryos became apparent during the heart stage of development, when embryos normally begin the rapid cell division and expansion required for the completion of morphogenesis. Despite their morphological abnormalities, mutant embryos often germinated from dry seed, demonstrating that genetic programs required for the establishment of desiccation tolerance remained intact. Mutant seedlings displayed a wide range of developmental abnormalities, including altered morphology, lack of pigmentation, dwarfism, and disorganized vegetative growth. One late mutant was found to be allelic to an early embryo defective that arrests at the globular stage. These results suggest that a number of late EMB genes encode basic cellular and metabolic functions needed for cell division, enlargement, and embryonic growth. The rapid growth and metabolic changes that occur at the heart stage may present a barrier to normal development in the late mutants, resulting in altered embryo morphology and other developmental defects. It is proposed that many Arabidopsis mutants with abnormal embryo and seedling morphology are not defective in the regulation of pattern formation or morphogenesis, but rather in fundamental physiological and cellular processes required for the completion of normal growth and development. © 1995 Wiley‐Liss, Inc.
cyd, a mutant of pea that alters embryo morphology is defective in cytokinesis
Authors: Liu Chun‐Ming , Johnson Sue , Wang Trevor L. 
Published: May 2005

AbstractEmbryogenesis in higher plants requires the precise regulation of cell division, orientation of cell elongation and specification of cell differentiation. The division plane is determined by the position of a new cell plate at cytokinesis. A mutant of pea has been isolated in which both the embryo pattern and surface morphology is altered. The phenotype of the mutant is manifest primarily in the cotyledons where cell plates only partially form, generating cell wall stubs and multinucleate cells. Some cotyledonary cells of the mutant proceed through nine DNA replication cycles, including nuclear division, but not cytokinesis, producing nuclei with a DNA content of ca. 1000C. The cytological phenotype of the mutant could be mimicked by the treatment of wild‐type cells with caffeine. We have termed this mutant cytokinesis‐defective (cyd). © 1995 Wiley‐Liss, Inc.
Transcription of the Zea mays homeobox (ZmHox) genes is activated early in embryogenesis and restricted to meristems of the maize plant
Authors: Klinge Bettina , Werr Wolfgang 
Published: May 2005

AbstractFour Zea mays homeobox (ZmHox) genes have been analyzed in their spatial expression pattern during development of the maize plant. The ZmHox1a or b and ZmHox2a or b gene pairs encode putative plant transcriptin factors; the mRNA transcripts belong to the rare class of mRNA molecules. Expression of the ZmHox1 and 2 genes is activated very early in embryonic development and restricted to the embryo proper in the proembryo stage. After establishment of the root/shoot axis, transcripts are prevalent in the embryonic root and shoot apical meristems but later are also found in provascular tissues and young leaf primordia. In the vegetative plant body the transcription of the ZmHox genes marks several types of meristems of the shoot and root system, the descending proliferating regions and provascular strands. Expression persists in the developing reproductive organs, but results obtained in the male flower indicate that transcription of ZmHox genes here may become confined to specific cell types. The data obtained during this study show that these four ZmHox genes are expressed very specifically in cells where developmental decisions contribute to the ontogeny of the maize plant. The overall expression pattern suggests that the ZmHox class of maize homeobox genes will be involved in transcriptional control during maize development from the embryonic to the reproductive phase. © 1995 Wiley‐Liss, Inc.
Effect of mutations in the PINHEAD gene of Arabidopsis on the formation of shoot apical meristems
Authors: McConnell Jane R. , Barton M. Kathryn 
Published: May 2005

AbstractThe primary shoot apical meristem of angiosperm plants is formed during embryogenesis. Lateral shoot apical meristems arise postembryonically in the axils of leaves. Recessive mutations at the PINHEAD locus of Arabidopsis interfere with the ability of both the primary shoot apical meristem as well as lateral shoot apical meristems to form. However, adventitious shoot apical meristems can form in pinhead mutant seedlings from the axils of the cotyledons and also from cultred root explants. In this report, the phenotype of pinhead mutants is described, and a hypothesis for the role of the wild‐type PINHEAD gene product in shoot meristem initiation is presented. © 1995 Wiley‐Liss, Inc.