bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA methylation in vegetative and conjugating cells of a protozoan ciliate: Blepharisma japonicum
Authors: Salvini M. , Barone E. , Ronca S. , Nobili R.
Published: May 2005

We report here the presence of N6‐methyladenine (MeAde) in the macronuclear DNA (maDNA) of Blepharisma japonicum vegetative cells. We have further investigated the relationship between DNA methylation and cell union in cells activated for conjugation. Such activation was induced by treating cells of mating type I with complementary gamone 2. We found a reduction of about 24% of MeAde content in gamone‐treated cells ready for cell union. First indications of the presence and reduction of MeAde content came from electrophoresis of maDNA digested by appropriate restriction endonucleases. Chromatographic determination of the amount of methylated base by HPLC substantiated these observations. In vegetative cells, 1.576 ± 0.02% of total adenine was found to be methylated as opposed to 1.193 ± 0.04% in activated cells. The HPLC analysis of maDNA also revealed a peak with a retention time corresponding to that of 5‐hydroxymethyluracil, already found in some species of dinoflagellates. In that gamone treatment is correlated with a differential gene expression (indicated by a differential RNA and protein synthesis), our results suggest that there is a relationship between macronuclear genome activation and demethylation of maDNA. This is the first report of a correlation between gene activation and adenine demethylation in a eukaryotic organism.
A cytokinin mutant derived from cultured tobacco cells
Authors: Meins Frederick , Foster Rachel
Published: May 2005

Tissues cultured from the leaf lamina of wild‐type Nicotiana tabacum L. cv. “Havana 425” plants require an exogenous source of cytokinin for rapid growth. In contrast, leaf tissues of plants heterozygous or homozygous for the partially dominant, monogenic habituated leaf (H1‐1) trait, exhibit a cytokinin‐autotrophic phenotype in culture. Here we show that the H1 trait can arise in culture. Cytokinin autotrophic variants were obtained by culturing wild‐type tissues of leaf lamina successively on media containing reduced concentrations of the cytokinin, kinetin. Plants regenerated from clones of these variants exhibited the H1 phenotype, which segregated in breeding tests as expected for a dominant, monogenic trait. This trait, designated H1‐2, is inherited at a different locus than the H1‐1 trait described earlier. Our results show that cytokinin mutants can arise in cell culture and that at least two genes regulate the cytokinin requirement of cultured tobacco tissues.
Changes in plant gene expression during stress
Authors: Matters Gail L. , Scandalios John G.
Published: May 2005

Changes in gene expression which occur during periods of environmentally induced stress provide models for the study of gene regulation. Several types of stress have been shown to elicit a specific and reproducible pattern of gene expression in various plant species. These stress factors include heat shock, anaerobiosis, plant pathogens, oxygen free radicals, heavy metals, water stress, and chilling. In some cases, changes in specific genes have been identified, such as increases in the expression of the gene encoding the phyto‐alexin‐synthesizing enzyme in pathogen elicitor‐treated cells. However, in most cases, the functional identity of stress‐induced genes is unknown. The alterations in gene expression during stress usually are rapid and repeatable, making these genetic systems ideal for examination of factors and mechanisms involved in gene regulation.
Sex ratio and testis size in mice carrying Sxr and T(X;16)16H
Authors: McLaren Anne
Published: May 2005

Mice heterozygous for the T(X;16)16H translocation and carrying Sxr on their normal (inactive) X chromosome (ie, T16H/X Sxr individuals) may develop as males, females, or hermaphrodites. The proportion of males varied from 22% to 65% depending on the source of the normal X chromosome. A model is proposed, according to which relatively small variations in the spreading of inactivation from the X chromosome into the attached Sxr fragment produce large changes in the proportion of males. Testis weight in T16H/X Sxr males was found to be significantly smaller than in X/X Sxr males, irrespective of the source of the normal X chromosome.
Description of an embryonic lethal gene, l(5)‐1, linked to Wsh
Authors: Papaioannou Virginia E.
Published: May 2005

A recessive lethal mutant linked to Wsh causes the death of homozygous embryos between 4.5 and 5.5 days postcoitum (pc). Histological examination of implantation sites from intercross and backcross matings indicates that homozygotes are not all evident at 4.5 days pc, when embryos have begun to form trophectoderm giant cells and primitive endoderm, but are degenerating by 5.5 days pc, with only a few primary giant cells remaining after this time. The mutants thus form blastocysts that initiate the implantation process but the inner cell mass and polar trophectoderm fail to develop further. In vitro examination and culture of blastocysts indicated that the mutant homozygotes hatch from the zona pellucida and outgrow, although they do so somewhat more slowly than normal embryos. After 3 days of culture, the inner cell masses of mutant outgrowths may be smaller than normal. Since the gene has no known heterozygous effect and the primary gene function remains unknown, the mutant has been given the provisional symbol l(5)‐1 for the first lethal on chromosome 5.
Influence of mouse trisomy 16 on expression of specific genes
Authors: Fundele Reinald , Winking Heinz , Jägerbauer Eva‐Maria
Published: May 2005

We examined developmental changes in the relative activities of three different isozyme systems: aldolase, enolase and phosphoglycerate mutase, in tissues of fetal mice with trisomy 16 and of fetal euploid littermates. We wanted to determine whether morphological abnormalities such as reduced weight and size, which are generally observed in murine trisomy, are reflected at the molecular level. Following electrophoretic separation and subsequent measurement of relative activities of enolase isozymes in brain and phospho‐glycerate mutase isozymes in heart, we found no significant differences between trisomy 16 fetuses and their euploid littermates. Synthesis of liver‐specific aldolase was, however, delayed in trisomy 16 fetuses.
Differential riboflavin deposition in white and variegated white mutants of Drosophila hydei
Authors: van Breugel Frans M. A.
Published: May 2005

Riboflavin deposition in organs of Drosophila hydei was studied by means of a growth test using a riboflavin‐deficient strain of the fungus Aspergillus nidulans. In wild‐type animals, riboflavin is deposited in Malpighian tubules (MT) and testes but not in adult eyes. Certain white (w) mutants do not contain riboflavin, whereas intermediately colored w mutants contain minor amounts of the substance. Riboflavin‐containing MT cells contain special globules that can be fixed and stained with the redox dye phenazine‐methosulphate. The number and size of these granules is related to growth effect and point to a role of the w locus in the intracellular deposition of riboflavin in special organs. In white‐mottled (wm) position‐effect variegation mutants, a significant correlation was found between the extent of variegation (percentage of yellow cells) and riboflavin content (growth effect) of the MT. However, the individual variation of cell phenotype was extremely large and exaggerated types were observed indicating “overdominance” of the rearranged w+ gene. This contradicts an unsubstantiated dogma of position‐effect variegation that assumes that the affected gene simply switches between the on and off state, as is discussed.
Tumor formation and morphogenesis on different Nicotiana sp and hybrids induced by Agrobacterium tumefaciens T‐DNA mutants
Authors: Nacmias B. , Ugolini S. , Ricci M. D. , Pellegrini M. G. , Bogani P. , Bettini P. , Inzé D. , Buiatti M.
Published: May 2005

A series of experiments are presented that have been performed to observe the interactions between Agrobacterium tumefaciens strains mutated in the T‐DNA genes involved in indoleacetic acid and cytokinin biosynthesis and several Nicotiana species and hybrids. Infections were induced on leaf cuttings of Nicotiana debneyi, N. knightiana, N. clevelandii, N. bigelovii var bigelovii, N. bigelovii var quadrivalvis, N. glauca, N. langsdorffii, the amphidiploid tumorous hybrid N. glauca × N. langsdorffii, and a nontumorous mutant of it. The effect of deletions of the Ti plasmid varied according to plant genotype. Insertion mutants in iaaM and iaaH suppressed tumor formation in N. langsdorffii, reduced it in N. bigeloviivar quadrivalvis, had no effect in N. glauca and the two amphidiploid hybrids, and promoted tumorigenesis when compared to the wild‐type Agrobacterium strain B6S3 in N. bigelovii N. debneyi, and N. knightiana. The same mutations induced shoot formation in N. glauca, increased it in N. debneyi, and suppressed root formation in N. knightiana. On the other hand, an insertion mutation of the isopentenyl transferase gene (ipt‐) had no effect in N. bigelovii var quadrivalvis, N. debneyi, the tumorous hybrid, suppressed tumor formation in N. langsdorffii, and inhibited it in N. glauca, the nontumorous hybrid, N. bigelovii var bigelovii, and N. knightiana. Insertion in ipt suppressed shoot formation in the nontumorous hybrid and inhibited it in the nontumorous amphidiploid and N. debneyi, while promoting root formation in N. glauca and N. debneyi.

The suggestion of the existence of specific hormone equilibria necessary for the shift to each morphogenetic pattern was supported by experiments with exogenous hormone treatments of three genotypes (N. glauca, N. langsdorffii, and the nontumorous N. glauca × N. langsdorffii).
The cellular basis of wing size modification in Drosophila: The effects of the miniature gene, crowding, and temperature
Authors: Kuo Tea , Larsen Ellen
Published: May 2005

To elucidate the mechanisms whereby genes and environment influence wing size, we investigated the effects of various rearing temperatures and larval crowding conditions on the wings of the mutant miniature and wild‐type fruit flies. In adults we monitored wing size, cell number, wing thickness, cell density; in larval imaginal discs we looked for cell death. Cell density was inversely proportional to wing size. Of particular interest was the finding that smaller wings tend to be thicker. Electron microscope studies showed that the miniature wing layers are grossly abnormal. We hypothesize that these abnormalities are due to abnormal cell flattening of the wing epithelial cells, and we conclude that gene and environmental effects on cell flattening may be an important component in determining cell density and hence organ size.
Allelic variation at the frizzled locus of Drosophila
Authors: Adler Paul N. , Charlton Jeannette , Vinson Charles
Published: May 2005

The epidermis of Drosophila has a tissue polarity that is manifested by a parallel array of polarized structures (primarily hairs and bristles). The production of normal tissue polarity requires the function of the frizzled (fz) locus. We have isolated a large number of alleles at this locus and have phenotypically characterized more than 25 of them. We have found extensive allelic variation that a previous study failed to detect. Most of the alleles fall into a hypomorphic to amorphic series. Two alleles, however, have unusual properties. These alleles, which in general are moderately strong alleles, fail to produce a rough eye phenotype that is characteristic of all the other moderate or strong fz alleles. Thus, these two alleles are tissue specific in effect. Furthermore, these two alleles also have a neomorphic or antimorphic effect on hair polarity in one region of the wing.
Post‐transcriptional regulation and DNA undermethylation of intracisternal A particle genes in embryonal carcinoma cell lines
Authors: Morgan Richard A. , Huang Ru Chih C.
Published: May 2005

Northern blot analysis and in vitro nuclear transcription assays were performed in order to clarify conflicting reports on the expression of intracisternal A particle (IAP) genes in embryonal carcinoma (EC) cell lines. Results demonstrate that post‐transcriptional mechanisms control the final steady‐state levels of IAP RNA in EC cells. IAP genes were further found to be undermethylated in IAP‐expressing EC cell lines.
Murine “housekeeping” enzyme (genetic locus:Idh‐1) is regulated in an allele‐specific manner
Authors: Zitnik G. D. , Martin G. M.
Published: May 2005

The murine “housekeeping” enzyme, cytosolic NADP‐isocitrate dehydrogenase (E.C. 1.1.1.42) (genetic locus:Idh‐1), exhibited a complex pattern of allele‐specific expression. Protein electrophoresis on cellulose‐acetate gels and determination of relative enzymatic activity by means of densitometry revealed that in heart tissue (but not liver tissue) of certain hybrid crosses the AA‐homodimer was underrepresented relative to total enzymatic activity, and the degree of underrepresentation changed during development. In mixtures of homozygous tissue extracts of heart tissue (but not liver tissue) the AA‐homodimer was underrepresented relative to the BB‐homodimer. Relative activity of allelic isozymes varied as a function of tissue (heart versus liver), age, and the parental source of the Idh‐1a allele, but did not vary as a function of sex.

Allele‐specific expression was also exhibited in kidney tissue of the same animals. In adult male kidney tissue extracts from heterozygotes, the AA‐hornodimer was underrepresented relative to total enzymatic activity; in adult female kidney tissue extracts from heterozygotes, a more codominant phenotype was observed. Tissue extracts from immature hybrid animals exhibited a phenotype midway between the adult male and adult female phenotypes. Tissue extracts from castrated males exhibited a phenotype equivalent to that seen in females. Relative activity of allelic isozymes in kidney varied as a function of age and sex, but did not vary as a function of the parental source of the Idh‐1a allele.

While cytosolic NADP‐IDH is a “housekeeping” enzyme, expressed in multiple tissues of the mouse, differences in the relative intensities of allelic isozyme bands provide evidence for tissue‐ and stage‐specific regulatory variation.
Action of the cubitus interruptus‐wallace mutant in Drosophila melanogaster: A study of leg morphology on mosaic and haplo‐4 flies
Authors: Benner D. B.
Published: May 2005

The fourth chromosome mutant cubitus interruptus‐Wallace(ciW) produces leg, wing, and body bristle aberrations. The effect on the wing is similar to that produced by cubitus interruptus‐dominant (ciD) which also has an influence on larval segmentation indicating that it has a regulatory function. Leg morphology of haplo‐4, ciW, and mosaic haplo‐4:diplo‐4, ci/ci+ flies was examined in an attempt to distinguish between a structural and a regulatory function by ciW. Aberrations recovered include failure of segment elongation, intersegmental gaps, duplication of bristles, and segments that are shorter than normal and of greater than normal diameter. Many of these effects are localized, suggesting that ciW may act to maintain cell positional reference. Increased local cell proliferation appears to be one manifestation of loss of the normal function.
Gene controlling a differentiation step in the quail melanocyte
Authors: Yamamoto Hiroaki , Ito Kazuo , Ishiguro Sei‐Ichi , Takeuchi Takuji
Published: May 2005

Albino mutation in animals blocks pigmentation owing to a deficiency in tyrosinase, although it does not affect the differentiation of colorless melanocytes from the neural crest. In the albino Japanese quail (al, sex‐linked), it was demonstrated that morphologically normal melanocytes differentiated from neural crest cells in culture and that these cells contained unmelanized melanosomes as expected for the mutant cells. The mutant melanocytes, however, were shown to exhibit tyrosinase activity in the Golgi‐endoplasmic reticulum‐lysosome region and in the Golgi vesicles. Our results seem to indicate that the mutation at the al locus affects the transport of tyrosinase from the Golgi area to melanosomes.
Influence of the major histocompatibility comp(MHC) on the response to and expression of H‐Y in rats
Authors: Desquenne‐Clark Lise , Chen Hong‐Duo , Silvers Willys K.
Published: May 2005

The influence of the major histocompatibility complex (MHC) on the survival of H‐Y‐incompatible skin grafts in rats has been determined by challenging normal and previously sensitized females of various isogenic and congenic strains with male trunk or ear skin isografts. The MHC's influence on the potency of H‐Y has also been evaluated by determining the survival of male parental strain ear skin grafts on sensitized (with F1 hybrid male cells) F1 hybrid females of two different MHC congenic strains. The results indicate that, as in mice, the MHC has a dual affect on H‐Y; it is involved in determining the ability of females to respond to the antigen as well as influencing its potency.
Tissue‐specific and developmental expression of human transthyretin gene in transgenic mice
Authors: Yamamura Ken‐Ichi , Wakasugi Shoji , Maeda Shuichiro , Inomoto Takeaki , Iwanaga Tomohisa , Uehira Masahiro , Araki Kimi , Miyazaki Jun‐Ichi , Shimada Kazunori
Published: May 2005

To analyze the regulation of transthyretin gene expression we have produced transgenic mice by microinjecting cloned human transthyretin genes into fertilized eggs of C57BL/6 mice. The 7.6‐kilobase (kb) human transthyretin gene containing about 500 base pairs (bp) in the upstream region was used for microinjection. Seven out of nine transgenic mice had detectable amounts of human transthyretin in serum when analyzed by enzyme‐linked immunosorbent assay.

Transthyretin mRNA was detected in liver and yolk sac but not in other tissues including brain. The amount of mRNA was variable among transgenic mice and was about one‐tenth of mouse endogenous transthyretin mRNA. Human and mouse transthyretin mRNAs were detected in liver of fetus and yolk sac at 13 days of gestation and unlike yolk sac the level of mRNA in liver increased gradually during development and reached the maximum at around 17 days of gestation. Human transthyretin was associated with mouse transthyretin to form tetramers as judged from the dilution curve of enzyme‐linked immu‐nosorbent assay and the spur formation in Ouchterlony assay.
Testes of XX ↔ XY chimeric mice develop from fetal ovotestes
Authors: Bradbury Michael W.
Published: May 2005

The majority of XX ↔ XY chimeric mice develop into fertile males. The sexual differentiation of the gonads in these animals has been examined on days 12–14 postcoitum to determine if their development parallels that of normal testes. It was found that 50% of chimeric fetuses, the proportion predicted to be XX ↔ XY, had neither normal testes nor ovaries. Instead, ovotestes were present, with varying proportions of presumptive ovarian and testicular tissue. On day 12 the ovotestes were organized with testicular tissue in the central region and ovarian tissue at the craniad and/or caudad poles. In the more advanced fetuses there was evidence of regression of the ovarian portion, which would account for the testes found in adults. These results are discussed in light of current theories of sex determination and differentiation and what was previously known about gonads of sex mosaics.
Restriction enzyme evidence for Alu sequence‐mediated dispersion of microinjected genes in transgenic mice
Authors: Rubinstein Wendy S. , Gordon Jon W.
Published: May 2005

A human bacteriophage clone containing adult β‐globin genes with four Alu sequences was microinjected to produce transgenic mice. Southern blot analysis on the spleen of a transgenic mouse revealed an unusual hybridization pattern that suggested extensive dispersion of human DNA throughout the mouse genome. This pattern was reproducible using several restriction enzymes, including a noncutting enzyme. The hybridization pattern was not observed in other tissues, and sequences were not detected in progeny using the bacteriophage probe. However, hybridization of spleen DNA of offspring against a human Alu probe revealed genetic transmission of human Alu sequences. The results suggest dispersion of microinjected Alu sequences throughout the genome.
Developmental consequences of autosomal aneuploidy in mammals
Authors: Gearhart John D. , Oster‐Granite Mary L. , Reeves Roger H. , Coyle Joseph T.
Published: May 2005

Autosomal aneuploidy in mammals adversely affects developmental processes. In human beings, for example, trisomy 21 is the most frequent aneuploidy detected among newborns and the most common known genetic cause of mental retardation. In this review, several hypotheses are discussed that have been proposed to explain the mechanisms by which aneuploidy (especially trisomy) disrupts development. These mechanisms included specific gene dosage effects, generalized disruption of genetic homeostasis, and the influence of the parental origin of the duplicated chromosome. The availability of specific chromosomal rearrangements in mice, coupled with selective breeding schemes, permits generation of aneuploidy of specific chromosomes or chromosomal segments on controlled genetic backgrounds, thus enabling the systematic study of the causes and consequences of defined aneuploidy. Phenotypic characteristics associated with a number of specific aneuploidies in the mouse are discussed. Emphasis is placed on the effects of trisomy 16. Genetic homology between mouse chromosome 16 and human chromosome 21 has led investigators to suggest that analogous mechanisms will be responsible for the developmental abnormalities produced in these respective aneuploidies. Analysis of trisomy 16 mice from the organismal to the subcellular level has revealed a number of phenotypic characteristics (particularly neurobiologic ones) shared with human trisomy 21. The dosage effects of shared genes (or their products) may contribute to the development of these features.
Cloning and developmental regulation of α1 acid glycoprotein in swine
Authors: Stone R. T. , Maurer R. A.
Published: May 2005

A cDNA clone of porcine alpha1 acid glycoprotein (α1AGP) has been isolated and sequenced. Sequence homologies between porcine, human, and rat indicate that porcine α1AGP is similar in structure to the rat and human proteins. RNA blots from days 40, 60, 80, and 110 fetal, newborn, and adult livers showed that α1AGP mRNA is relatively abundant throughout fetal development, particularly at the later stages and in the newborn; there is a rapid decline in abundance following birth. From birth to 3 days of age, there is a three‐ to four‐fold decline in abundance, and α1AGP mRNA is approximately 100 times less abundant in the adult liver than in that of perinatal pigs. Southern blots showed that α1AGP is probably a single‐copy gene. The isolation of a cloned cDNA for porcine α1AGP provides a tool to investigate the molecular mechanisms involved in the developmental regulation of the gene and to correlate changes in gene expression during development with fetal growth and well being.
Use of nuclear mutants in the analysis of chloroplast development
Authors: Taylor William C. , Barkan Alice , Martienssen Robert A.
Published: May 2005

Although a wide range of mutations in the nuclear genome also affect chloroplast biogenesis, their pleiotropic nature often limits their use in studying nuclear genes that regulate or facilitate chloroplast development. However, many mutations that cause a high‐chlorophyll‐fluorescent (hcf) phenotype exhibit limited pleiotrophy, causing the loss of functionally related sets of chloroplast polypeptides. Several hcf mutations are described that result in the loss of one specific protein complex from the thylakoid membrane. Chlorplast and cytosolic mRNAs coding for component polypeptides of the missing complex are unaffected in the mutants, suggesting that each mutation disrupts some process in the synthesis and assembly of the missing complex. Another hcf mutation causes both the loss of three protein complexes and grossly abnormal thylakoid membrane structures. The primary effect of this mutation might be in the assembly of thylakoid membranes or in the stable accumulation of the three protein complexes. Two other hcf mutations are more pleiotropic. Hcf*−38 causes a quantitative reduction of many chloroplast proteins and a reduction of some chloroplast RNAs, including several splicing intermediates. Hcf*−7 causes a major reduction of all chloroplast‐encoded proteins examined. The range of pleiotropic effects of hcf mutations indicates that the mutations identify nuclear genes whose products are involved in a number of different steps in chloroplast devclopment. Because some of the mutations described have been generated by transposon insertions, they can be cloned using the transposon to identify the mutant allele.
Structure of the chloroplast psbA gene encoding the QB protein from Oryza sativa L.
Authors: Wu Nai‐Hu , Côté Jean‐Charles , Wu Ray
Published: May 2005

The light‐regulated chloroplast psbA gene encoding the QB protein has been cloned from rice (Oryza sativa L.), and the nucleotide sequence has been determined. Comparison of nucleotide sequences and derived amino acid sequences between species indicates a high degree of conservation of the primary structure. Comparison of promoter regions from the light‐inducible chloroplast psbA, rbcL, and psaA genes indicates conservation of the prokaryotic‐like promoter elements in all three genes and of a —21 box common only to psbA and rbcL promoter regions. No other putative regulatory signals were found based on nucleotide sequences.
Auxin (2,4‐dichlorophenoxyacetic acid) starvation and treatment with glucan elicitor isolated from Phytophthora megasperma induces similar responses in soybean‐cultured cell suspensions
Authors: Leguay J. J. , Jouanneau J. P.
Published: May 2005

Auxin (2,4‐dichlorophenoxyacetic acid) starvation of soybean cell suspension leads to the arrest of cell division after about 4 days. Readdition of 4 μM of auxin enables cells to divide again after a lag phase of 1 day. Accumulation of a well‐known isoflavonoid‐derived phytoalexin (glyceollin) and a highly elevated catalytic activity of two of the enzymes associated with glyceollin biosynthesis, phenylalanine ammonia‐lyase and chalcone isomerase, is described. Moreover, stimulation of catalytic activity of the enzymes chitinase and β 1,3‐glucanase, which are involved in plant defense against pathogens, is observed at the same time. By comparing the patterns of in vitro protein synthesis, we have identified groups of polypeptides whose synthesis is either positively or negatively regulated by auxin. Some of these polypeptides are also induced by fungal elicitor treatment. Our results provide evidence of a dual control by auxin and fungal elicitor working in an opposite manner on the inducibility of enzymes and proteins that play a role in the induced defense response of soybean.
Developmental genetics of the soybean urease isozymes
Authors: Holland Mark A. , Griffin Jeffrey D. , Elise Meyer‐Bothling L. , Polacco Joseph C.
Published: May 2005

The soybean (Glycine max [L.] Merr.) contains two urease isozymes whose expression is regulated in a tissue‐specific and temporal manner. The ubiquitous urease is expressed in all tissues examined (leaf, embryo, seed coat, cell culture); the embryo‐specific urease is synthesized exclusively in the developing embryo. The embryo‐specific urease accumulates during seed development while the ubiquitous urease is found in highest levels during early development of both leaves and seeds. We have isolated mutants which fall in three phenotypic classes lacking one or both urease isozyme activities. Genetic analysis has thus far identified three unlinked loci which control the expression of urease(s). Genomic and cDNA clones of urease structural genes have also been recovered and we are working to assign these to genetic loci by sequence and RFLP analyses. That the ubiquitous urease isozyme is expressed in cell culture makes it possible to include cell culture in physiological and developmental studies. Additionally, we have developed direct selections for urease‐negative mutants, and their revertants, in cell culture. These selections will facilitate the study of the expression of cloned urease genes in genetically transformed tissue.
Nuclear genes that alter assembly of the chlorophyll a/b light‐harvesting complex in Zea mays
Authors: Polacco Mary , Vann Carolyn , Rosenkrans Leonard , Harding Scott
Published: May 2005

The major chlorophyll a/b light harvesting complex (LHCII) of mesophyll chloroplasts is normally assembled late during chloroplast morphogenesis. LHCII occurs at greatly reduced levels in bundle sheath chloroplasts of maize. In order to understand the normal regulatory mechanisms we are examining nuclear maize mutants that alter either (1) the assembly timing or (2) the steady state level of LHCII in mature mesophyll thylakoids. We have found a delayed greening mutant, v24 (on chromosome arm 2L), that unmasks a second unlinked locus, Mof*, that can mediate LHCII assembly timing. The polypeptides of LHCII are encoded by the nuclear multigene cab family. We find that two alleles at Mof* regulate the steady state level of cab mRNA in parallel to their effect on LHCII assembly timing: The genotype Mof*‐1 Mof*‐1 v24 v24 corresponds to reduced cab mRNA and late LHCII assembly timing, while Mof*‐2 Mof*‐2 v24 v24 corresponds to reduced cab mRNA and late LHCII assembly timing. A second group of mutations (Oy‐700, pg11 and pg12 reduces LHCII levels in mesophyll thylakoids. This is the first report that pg11 and pg12) reduce the LHCII of mesophyll thylakoids. The basis of pg11 and pg12 is unknown. Mutations at the Oy locus block the chlorophyll biosynthetic enzyme, protopor‐phyrin IX Mg‐chelatase. Heterozygotes of the codominant mutation Oy‐700 with the normal allele (Oy) have reduced LHCII. We have defined genetic backgrounds that suppress and those that do not suppress the Oy‐700 Oy phenotype under certain conditions: (1) reduced light intensities (200 μE cm−2 sec−1) and/or (2) plant maturity.
Histone genes in higher plants: Organization and expression
Authors: Chaubet Nicole , Chaboute Marie‐Edith , Philipps Gabriel , Gigot Claude
Published: May 2005

The general structure of the plant histone genes has been deduced from the comparison of the nucleotide sequences of ten H3 and H4 genes of maize (3 H3 and 3 H4) and Arabidopsis thaliana (2 H3 and 2 H4). The five H3 and five H4 genes encode the same proteins, respectively. The 5′‐flanking regions contain the classical histone gene‐specific consensus sequences. In addition, a conserved octanucleotide CGCGGATC was found in all plant histone genes at 200–250 nucleotides before the initiation codon.

All six maize H3 and H4 genes are transcribed during early germination as shown by nuclease S1 mapping and reverse transcriptase primer extension experiments. The mRNA 5′‐ends are located within the consensus sequence CCAA/CT/C. The 3′‐ends lack the classical T‐hyphenated dGC‐rich palindromic structure and possess long nontranslated sequences.

In both plants the multiple copies of the H3 and H4 genes are organized into multigenic families. The genes of each family show a similar proximal environment, suggesting that they originate from the duplication of a common ancestor.
Expression of selected nuclear genes during leaf development in barley
Authors: Barkardottir R. B. , Jensen B. F. , Kreiberg J. D. , Nielsen P. S. , Gausing K.
Published: May 2005

Groups of cDNA clones encoding abundant leaf proteins or derived from genes (gene families) with other features of interest have been selected from a barley leaf cDNA library. The characteriaztion of nine of the groups is summarized and includes information on the tissue specificity and light dependence of expression of their corresponding genes. Different types of control of gene expression are represented in the collection: leaf‐specific expression, both stimulated and inhibited by light, constitutive expression, and expression that is maximal in one case in coleoptiles and in two cases in meristematic tissue. For the light‐stimulated genes (gene families) encoding chloroplast proteins (Cab, RbcS, and plastocyanin), relative and absolute levels of messengers were determined as a function of cell age in sections of 7‐day‐old barley leaves grown under diurnal conditions. Key parameters of cell growth (protein, RNA, and DNA accumulation) were determined in the same leaf sections. The main conclusions of the expression studies are as follows: (1) Light is in no case a requirement for gene expression although it has significant stimulatory effect on some genes; (2) weak expression of some genes coding for chloroplast proteins was detected in the leaf‐like, white coleoptiles, whereas expression in roots could not be detected; (3) The cab, rbcS, and plastocyanin genes are expressed very early during leaf cell differentiation, when the plastids morphologically are still in their amyloplast‐amoeboid stages; (4) The expression of the cab, rbcS, and plastocyanin genes is not coordinated during leaf cell development.
Age‐dependent variation for inducibility of metallothionein genes in mouse liver by cadmium
Authors: Thomas David J. , Morris Sheldon , Huang P. C.
Published: May 2005

Cadmium is a toxic metal that induces the expression of metallothionein genes in many tissues and that binds avidly to metallothionein, a soluble transition metal binding protein. The present study examined the temporal pattern and magnitude of accumulation of metallothionein mRNA in liver of C57BL/6J mice of various ages treated with cadmium. In adult female mice, accumulation was dependent on the dosage level of cadmium and related to the concentration of this metal in liver. The accumulation of metallothionein mRNA in liver depended on age at exposure to cadmium. Intraperitoneal administration of 2 mg of cadmium per kg provoked small increases (two‐ to threefold) in levels of metallothionein mRNA in livers of 7‐ and 14‐day‐old mice. In contrast, cadmium treatment of 28‐ and 56‐day‐old mice resulted in 12‐ to 19‐fold increases in levels of metallothionein mRNA in liver with maximum increases occurring 3 to 4 hr after treatment. Because similar patterns for the accumulation of cadmium of liver were found in 7‐, 28‐, and 56‐day‐old mice, observed age‐dependent differences in induction of metallothionein mRNA in liver were probably not due to differences in the accumulation of cadmium in this organ. Taken together, these data suggest that tissue‐specific factors controlling the expression of metallothionein genes may account for developmental variation in the inducibility of these genes by cadmium. Ontogenic variation in accumulation of metallothionein mRNA after cadmium treatment may be a factor in developmental variation in the acute lethality of cadmium in C57BL/6J mice.
Drosophila genes encoding maternal‐specific and maternal‐differential RNAs
Authors: Underwood Eileen M. , Lengyel Judith A.
Published: May 2005

The unique cellular and genetic events which occur during the first few hours of Drosophila embryogenesis suggest that there are genes whose function is entirely or largely limited to this stage; this is supported by both genetic and molecular evidence. To identify some of these genes and characterize the relative contribution of specifically maternal and specifically zygotic transcription to early embryogenesis, we used competition and differential screening of a Drosophila genomic DNA library to obtain blastoderm‐ and maternal‐differential sequences [Roark et al.: Dev Biol 109:476–488, 1985]. We describe here the Eco RI restriction fragments, chromosomal location, and size and developmental pattern of expression of the RNAs transcribed from 19 maternal‐differential sequences. Five sequences encode maternal‐specific transcripts (50‐150‐fold more abundant in maternal RNA than at any other stage). The maternal‐specific and maternal‐differential sequences are located at single sites on all major chromosome arms. Comparison of these sites with the sites of presently mapped maternal‐effect genes shows several possible correlations, including one region containing three maternal‐effect lethal mutations and two maternalspecific sequences.
Genetic analysis of somatic embryogenesis in carrot cell culture: Initial characterization of six classes of temperature‐sensitive variants
Authors: Schnall Jennifer A. , Cooke Todd J. , Cress Dean E.
Published: May 2005

Cell cultures of the carrot Daucus carota are a useful experimental system for studying the genetic regulation of plant embryogenesis. A modified filtration‐enrichment procedure was used to isolate 21 temperature‐sensitive variants in somatic embryogenesis; the variants display normal embryo development at the permissive temperature (24°C) and altered development at the restrictive temperature (33°C). Temperature‐shift experiments were performed on these variants to determine the timing of gene action for the putative temperature‐sensitive alleles. According to their phenotypes at the restrictive temperature, these variants can be divided into six classes: No Growth, Callus Proliferation, Globularstage Block, Oblong‐stage Block, Lateral Growth, and Root Formation. Although many variants exhibit lengthy temperature‐sensitive periods, the temperature sensitivity of some variants is restricted to one or two embryonic stages. These results plus those in the literature are incorporated into a preliminary model concerning the genetic regulation of carrot embryogenesis.
Quantitative evaluation of coat‐color patterns in artificially produced chimeras of the mouse by means of a microcomputer‐based video‐image analysis system
Authors: Tachi Chikashi
Published: May 2005

The possible application of microcomputer‐based video‐image analysis systems for the quantitative description of coat‐color patterns in artificially produced chimeras and genetic mosaics of mice was investigated using a program developed by theauthor. This system is capable of extracting, from sampled images of pelts, the morphometric image features as defined by Pratt [1978] that are essential to the quantitative description of coat‐color patterns in these animals. It does so with reasonable accuracy and speed and at low cost. No description of any similar system has been published in the literature. Performance of our system is described using C3H/HeJ ↔BALB/c chimeras as examples.

The complex phenotypic expression of hair pigmentation in mice makes the use of a video‐image analysis system like this one essential to evaluate the morphometric parameters of the patterns (e.g., the mixing ratios between the two components, the number of different‐colored stripes, etc.) more precisely and reproducibly than has been done yet in the literature.

The results indicate that the number of melanoblast clones in mice, as estimated from the number of minimal recognizable stripes (MRS), might be considerably largerthan previously indicated; the figure presently obtained, i.e., 22.3 ± 2.16 unilaterally in terms of the hypothetical maximum number of stripes (HMNS) (28.73 ± 1.55, after correction for the random clumping) in the thoracicolumbar region of the mouse closely approximates the number of the somites in that region. Concerning the degree of mixing between the two components, it was proposed that the unmixed portion of the components derived from one strain increases in proportion to the second power of the increase in the relative total content of the same components. Work is in progress in our laboratory to analyze a large number of the chimeric pelts using the system described in this paper.
Investigation of the tissue specificity of the lethal yellow (Ay) gene in mouse embryos
Authors: Papaioannou Virginia E.
Published: May 2005

The tissue specificity of the lethal yellow mutant was investigated by separation of blastocyst tissues. Embryos from experimental (Ay/ae × Ay/ae) and control (ae/ae × Ay/ae) crosses of the AG/CamPa inbred strain were recovered at 3.5 days post coitum, cultured for 24 hours, and then mechanically dissected into the component tissues of the blastocyst, the inner cell mass (ICM), and trophectoderm. These fragments were then cultured separately, with or without a feeder layer of inactivated fibroblasts, for an additional 3–5 days. Comparisons between experimental and control crosses indicated that the lethal Ay/Ay embryos were among the blastocysts successfully dissected but that both the ICM and trophectoderm from lethal embryos failed to develop further in vitro, eithal with or without feeders.

With retrospective identification of the lethal embryos, it was found that at 4.5 days, after 1 day of culture, they had formed morphologically normal blastocysts but were frequently more fragile upon dissection and had smaller ICMs. Although none had hatched from the zona pellucida, some had ruptured it and were halfway out. With culture, lethal ICMs showed no development, and lethal trophectoderm usually attached but showed very limited outgrowth. Thus, no rescue of lethal tissue was shown with dissection and in vitro culture, and results are consistent with the gene affecting both tissues of the late blastocyst.
Minute mutations of Drosophila melanogaster change aldehyde oxidase and pyridoxal oxidase distribution patterns in imaginal wing discs
Authors: Van Zijll Langhout Bart W. , Sprey Thomas E.
Published: May 2005

Aldehyde oxidase (AO) and pyridoxal oxidase (PO) distribution patterns were determined in the imaginal wing discs for a series of strains of Drosophila melanogaster heterozygous for different Minute mutations. The mutant severity ranged from very weak to strong. The results show an inverse response of AO and PO to the expressivity of the Minute mutation: in weaker Minutes the extent of the AO positive area increases, whereas PO activity disappears. The results are discussed with reference to an impaired protein synthesis in Minutes.
An autosomal dominant mutation of facial development in a transgenic mouse
Authors: Wakasugi Shoji , Iwanaga Tomohisa , Inomoto Takeaki , Tengan Toshimoto , Maeda Shuichiro , Uehira Masahiro , Araki Kimi , Miyazaki Junichi , Eto Kazuhiro , Shimada Kazunori , Yamamura Ken‐Ichi
Published: May 2005

We have created a transgenic mouse which showed an autosomal dominant mutation of facial development. This facial malformation was characterized by a short snout and a twisted upper jaw. All offspring showing the dysmorphic phenotype carried the injected gene. In order to analyze the primary cause of this mutation, newborn mice and embryos were examined. The outcome was that the malformation of nasal and premaxillary bone was not the primary defect but was a secondary event. The primary cause of this dysmorphism was a developmental defect in the first branchial arch. Genomic DNA fragments flanking the insertion site of this mutant mouse were cloned. Using these fragments, we have assigned the integration site to chromosome 13. The gene responsible for a previously reported mutant mouse, one which also has a short snout, is also reported to be on chromosome 13. In the fragments flanking the insertion site of the transgenic mouse, at least one fragment was highly conserved in mammals. These results indicate that this malformation is due to the insertional disruption of a host gene. However, the possibility that this mutation is caused by an inappropriate expression of the injected gene still remains to be investigated.
cAMP‐dependent protein kinase from Dictyostelium discoideum
Authors: Veron Michel , Mutzel Rupert , Lacombe Marie‐Lise , Simon Marie‐Noëlle , Wallet Valérie
Published: May 2005

The cAMP‐dependent protein kinase (cAK) from Dictyostelium discoideum is an enzyme composed of one catalytic and one regulatory subunit. Upon binding of cAMP, the holoenzyme dissociates to liberate free active catalytic subunits. The cAK is developmentally regulated, ranging from very little activity in vegetative cells to maximal expression in postaggregative cells. Although there is no immunological cross‐reaction between the subunits of cAKs from Dictyostelium and from other organisms, they share several biochemical properties. A complete cDNA for the regulatory subunit has been cloned and sequenced. Only one copy of the gene for the regulatory subunit is present per haploid genome. On the basis of the comparison of the structure of the cAK from Dictyostelium with its counterparts in yeast and higher eukaryotes, we propose a model for the evolution of cyclic‐nucleotide‐binding proteins.
Genes encoding novel GTP‐binding proteins in Dictyostelium
Authors: Saxe Stephen A. , Kimmel Alan R.
Published: May 2005

We have identified a two‐member gene family in the Dictyostelium genome and have isolated corresponding cDNA or genomic DNA recombinant clones. Analyses of these DNA sequences predicted encoded proteins of ∼︁200 amino acids with ∼︁90% sequence identity to each other. These Dictyostelium proteins also share amino acids identity within the GTP‐binding domains in the family of G‐regulatory proteins involved in cellular regulation and transmembrane signalling. Additional structural similarities are seen with members of the ras supergene family, such as ras, ral, and rho. They are similar in size (usually ∼︁200 amino acids), possess four conserved domains involved in GTP interaction and are believed to be anchored in the membrane by fatty acid modification of a cysteine residue near the carboxy terminus. More extensive identity is observed with YPT1 and SEC4, two other members of this family of genes that are essential in yeast. The amino‐terminal half of both Dictyostelium proteins is 70% identical in amino acid sequence to the YPT1 and SEC4 yeast proteins with less identity continuing through the remainder of the proteins. In addition these proteins terminate in two cysteine residues that are thought to be required for membrane anchorage.

The two genes within this Dictyostelium family are organized differently in the genome and are differentially regulated during development. One gene is colinear in sequence with its mRNA in the protein coding region, whereas the other gene encodes a spliced mRNA. The intron‐containing gene is associated with a developmentally regulated (AAC)‐repeat sequence. Finally, we have shown that the expression of one of the genes is induced during development with kinetics similar to that of other (AAC)n‐associated genes; conversely, the expression of the second gene is repressed at a similar developmental stage.