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PubMed2000

Ontogeny of a photic response in the retina and suprachiasmatic nucleus in the mouse.

The ontogeny of photic responsiveness in the retina and the suprachiasmatic nucleus (SCN) of C57BL/6J mouse was studied using the enhanced expression of the immediate early gene c-fos as a marker of neuronal activation. c-fos expression was assessed by immunocytochemical localisation of its protein product. Light induction of Fos-like protein in the retina and SCN occurred first at postnatal day four (PD 4). At this stage of development, some cells in the inner part of the neuroblastic layer and in the ganglion cell layer showed positive immunoreaction; the number of Fos-like positive cells increased with age until it reached adult levels by PD 15. Induction of Fos-like expression at PD 4 in the SCN mainly occurred in the ventrolateral region, the region that receives the greatest density of retinal innervation. These results indicate that retinal input can activate cells in the SCN even before eyelids open, and the SCN can be stimulated by photic inputs as early as day 4 after birth.

Adaptation, Ocular↗
PubMed2000

The fungal GATA factors.

The DNA-binding domains of eucaryotic GATA factors comprise a four-cysteine Zn finger and an adjacent basic region. Fungal GATA factors regulate nitrogen metabolism, light induction, siderophore biosynthesis and mating-type switching. Hydrophobic interactions determine binding-site specificity. Interactions with other factors may determine promoter specificity. One GATA factor has recently been shown to determine a drastic chromatin rearrangement.

Amino Acid Sequence↗
PubMed1974

The sites of transcription and translation for Euglena chloroplastic aminoacyl-tRNA synthetases.

We find that cycloheximide completely blocks the light-induced apearance of Euglena chloroplastic aminoacyl-tRNA synthetases in dark-grown cells of Euglena gracilis var. bacillaris. Streptomycin, on the other hand, has no effect on the light-induction of these organellar enzymes. These observations, together with the finding that an aplastidic mutant (strain W(3)BUL, which has neither significant plastid structure nor detectable chloroplast DNA) contains low levels of the chloroplastic synthetases, indicate that the chloroplastic synthetases are transcriptional products of nuclear genes and are translated on cytoplasmic ribosomes prior to compartmentalization within the chloroplasts.

Amino Acyl-tRNA Synthetases↗
PubMed2003

Construction of gene expression system in hop (Humulus lupulus) lupulin gland using valerophenone synthase promoter.

The promoter region of the valerophenone synthase (VPS) gene was isolated from hop (Humulus lupulus). VPS, a member of the chalcone synthase (CHS) super-family, catalyzes the biosynthesis reaction of the hop resin that significantly accumulates in the cone's secretory gland called the "lupulin gland". The typical H-box and G-box sequences, which exist in many plants' CHS promoters and act as cis-elements for tissue specificity, UV-light induction, etc., were not found in the isolated VPS promoter, although the H-box-like sequence (CCTTACC, CCTAACC) and the core sequence (ACGT) of the G-box were observed. The transformation experiment using the VPS promoter-UIDA gene fusion revealed that the promoter acts not only in the lupulin gland but also in the glands of leaf and stem. On the other hand, the VPS promoter activity was not induced by UV-irradiation.

Acyltransferases↗
PubMed1996

Proton pump and auxin effect in Arabidopsis thaliana leaves during the development.

The plasma membrane from Arabidopsis thaliana leaves (wild-type and F mutant) has been purified by two-phase partitioning and the H(+)-transport activity was tested in vitro in the presence of different concentrations of IAA. While 1 microM of IAA had no effect, higher concentrations (10 microM and 100 microM) were inhibitory in 25 short days grown wild-type plants. However, the activity was increased by about 16% after 10 supplementary short days of growth (from 25 to 35 SD) in the represence of 10 microM of IAA. No significant sensitivity to the tested concentrations of auxin was observed during the development in short days (30, 38, 42 SD) or even the plants were induced by a 24 h of continuous light. The variability was not observed for a given developmental stage, from one experiment to another, but it was also observed after light induction of F mutant plants.

Arabidopsis↗
PubMed1998

Circadian expression of the maize catalase Cat3 gene is highly conserved among diverse maize genotypes with structurally different promoters.

The Cat3 gene of maize exhibits a transcriptionally regulated circadian rhythm. In the present study we examined the following: (1) the extent of the circadian Cat3 expression between maize genotypes of diverse origin; (2) the functional significance of a Tourist transposable element located in the Cat3 promoter of the inbred line W64A, which harbors putative regulatory elements (GATA repeat, CCAAT boxes) shown to be involved in the light induction and circadian regulation of the Arabidopsis CAB2, as well as other plant genes; and (3) aspects of the physiological role of CAT-3 in maize metabolism. Results confirm that the circadian Cat3 expression is a general phenomenon in maize. Regulation of Cat3 gene expression is not dependent on the presence of the Tourist element in the promoter of the gene nor on the presence of motifs similar to those found significant in the circadian expression of the Arabidopsis CAB2 gene. Structural diversity was revealed in the Cat3 promoters of maize genotypes of diverse origins. However, highly conserved regions with putative regulatory motifs were identified. Relevance of the conserved regions to the circadian regulation of the gene is discussed. Possible physiological roles of CAT-3 are suggested.

Arabidopsis Proteins↗
PubMed1991

In vivo UV cross-linking of U snRNAs that participate in trypanosome trans-splicing.

The maturation of mRNAs in Trypanosoma brucei involves a trans-splicing reaction whereby the 5' 39 nucleotides of a small RNA, called the spliced leader (SL) RNA, are joined with a pre-mRNA transcript. The trans-splicing reaction appears mechanistically similar to cis-splicing of nuclear pre-mRNAs, and homologs of the U2, U4, and U6 snRNAs are required for the process. In the work presented here, potential RNA-RNA interactions between the SL RNA and the U snRNAs of trypanosomes were examined by UV light induction of RNA-RNA cross-links in vivo. We detected cross-linkage between U2 and U6 RNAs and, as might be expected, between the trypanosome U4 and U6 RNAs. The latter contain extensive sequence complementarity and are thought to exist predominantly in a single RNP. We also detected an SL RNA species following in vivo UV treatment, which may represent either an intramolecular cross-link in the SL RNA or a cross-link formed between the SL RNA and an as yet unidentified small RNA. Mapping of the cross-link position between U2 and U6 RNAs is consistent with base-pairing between the 5' domain of U2 and the 3' end of U6 RNA. These results reveal the existence, in vivo, of cognate RNA-RNA interactions in the RNA homologs that participate in trans-splicing in trypanosomes and cis-splicing in other eukaryotes.

Animals↗
PubMed1993

Structure and expression of chloroplast-localized porphobilinogen deaminase from pea (Pisum sativum L.) isolated by redundant polymerase chain reaction.

Porphobilinogen (PBG) deaminase catalyzes the polymerization of four PBG monopyrrole units into the linear tetrapyrrole hydroxymethylbilane necessary for the formation of chlorophyll and heme in plant cells. Degenerate oligonucleotide primers were designed based on amino acid sequence data (generated by mass spectrometry) for purified PBG deaminase from pea (Pisum sativum L.) chloroplasts. These primers were used in TaqI polymerase-catalyzed polymerase chain reaction (PCR) amplification to produce partial cDNA and nuclear genomic fragments encoding the enzyme. Subsequently, a 1.6-kb cDNA was isolated by screening a cDNA library constructed in lambda gt11 from leaf poly(A)+ RNA with the PCR products. The cDNA encodes an approximately 40-kD polypeptide containing a 46-amino acid NH2-terminal transit peptide and a mature protein of 323 amino acids. The deduced amino acid sequence of the mature pea enzyme is similar to PBG deaminases from other species and contains the conserved arginine and cysteine residues previously implicated in catalysis. Northern blot analysis indicates that the pea gene encoding PBG deaminase is expressed to varying levels in chlorophyll-containing tissues and is subject to light induction.

Amino Acid Sequence↗
PubMed1994

Phytochrome A and Phytochrome B Have Overlapping but Distinct Functions in Arabidopsis Development.

Plant responses to red and far-red light are mediated by a family of photoreceptors called phytochromes. In Arabidopsis thaliana, there are genes encoding at least five phytochromes, and it is of interest to learn if the different phytochromes have overlapping or distinct functions. To address this question for two of the phytochromes in Arabidopsis, we have compared light responses of the wild type with those of a phyA null mutant, a phyB null mutant, and a phyA phyB double mutant. We have found that both phyA and phyB mutants have a deficiency in germination, the phyA mutant in far-red light and the phyB mutant in the dark. Furthermore, the germination defect caused by the phyA mutation in far- red light could be suppressed by a phyB mutation, suggesting that phytochrome B (PHYB) can have an inhibitory as well as a stimulatory effect on germination. In red light, the phyA phyB double mutant, but neither single mutant, had poorly developed cotyledons, as well as reduced red-light induction of CAB gene expression and potentiation of chlorophyll induction. The phyA mutant was deficient in sensing a flowering response inductive photoperiod, suggesting that PHYA participates in sensing daylength. In contrast, the phyB mutant flowered earlier than the wild type (and the phyA mutant) under all photoperiods tested, but responded to an inductive photoperiod. Thus, PHYA and PHYB appear to have complementary functions in controlling germination, seedling development, and flowering. We discuss the implications of these results for possible mechanisms of PHYA and PHYB signal transduction.

Journal Article↗
PubMed1995

Nucleotide sequence and expression of the genes for the alpha and beta subunits of phycocyanin in Cyanidium caldarium.

The nucleotide sequence of the plastid-encoded operon containing genes for the alpha (cpcA) and beta (cpcB) subunits of phycocyanin in the unicellular red alga Cyanidium caldarium is described. cpcB is located 5' to cpcA and the two genes are separated by a 102-bp spacer region. The transcription start site of cpcBA was mapped to 80 bp upstream of the ATG initiation codon of cpcB. Promoter-like elements similar to the -10 (TATAAT) and -35 (TTGACA) consensus promoters in bacteria were found 6 and 31 bp upstream of the transcription initiation site. Northern blotting revealed an abundant 1.3-kb cpcBA transcript in illuminated cells, but this transcript was undetectable in dark-grown cells. Expression levels of cpcBA in cells incubated with 10(-6) M heme in the dark were similar to those in cells illuminated for 24 h. Cells illuminated with 150 microM gabaculine (an inhibitor of delta-aminolevulinate synthesis) or 10 mM levulinic acid (an inhibitor of delta-aminolevulinate dehydrase) lacked detectable cpcBA transcripts. In cells illuminated with 200 microM N-methyl-mesoporphyrin IX (an inhibitor of ferrocheletase), inhibition of cpcBA expression and phycocyanin synthesis was similar. These results provide strong evidence that light induction of the cpcBA operon is dependent on synthesis of heme.

Amino Acid Sequence↗
PubMed1996

Regulation of the Expression of the Glycine Decarboxylase Complex during Pea Leaf Development.

The expression of the genes encoding the four proteins (P, H, T, and L) of glycine decarboxylase, a multienzymatic complex involved in the mitochondrial step of the photorespiration pathway, was examined during pea (Pisum sativum) leaf development in comparison with ribulose-1,5-bisphosphate carboxylase/oxygenase. Mitochondria from the primary leaf were isolated at several well-defined stages of development. Their capacity to oxidize glycine was negligible during the earlier stages but increased dramatically once the leaflet opened. This was correlated with the accumulation of the glycine decarboxylase complex (GDC) proteins, which was shown to occur in preexisting mitochondria, producing an increase in their density. The transcription of the GDC genes was coordinated and occurred early, with a peak at 7 d, a stage at which mitochondria are unable to oxidize glycine. This implies the existence of posttranscriptional control of gene expression. The comparison of the expression patterns of the genes encoding specific proteins of GDC with that of rbcS genes suggests a common regulation scheme that is related to light induction. However, ribulose-1,5-bisphosphate carboxylase/oxygenase is present in the chloroplast well before GDC fills the mitochondria, suggesting that the setup of photorespiration occurs in cells already engaged in active photosynthesis.

Journal Article↗
PubMed1997

Isolation of a cDNA and a genomic clone encoding cinnamate 4-hydroxylase from Arabidopsis and its expression manner in planta.

We have isolated a cDNA for a cytochrome P450, cinnamate 4-hydroxylase (C4H), of Arabidopsis thaliana using a C4H cDNA from mung been as a hybridization probe. The deduced amino acid sequence is 84.7% identical to that of mung bean C4H and therefore was designated CYP73A5. The CYP73A5 protein was expressed in insect cells using the baculovirus expression system and when reconstituted with lipid and NADPH-cytochrome P450 reductase resulted in C4H activity with a specific activity of 68 nmol min-1 nmol-1 P450. Southern blot analysis revealed that CYP73A5 is a single-copy gene in Arabidopsis. C4H (CYP73A5) expression was apparently coordinated in Arabidopsis with both PAL1 and 4CL in response to light and wounding. Although the light induction of CHS followed a time course similar to that observed with C4H, no induction of CHS was detected upon wounding. On the other hand, the C4H expression patterns exhibited no significant coordination with those of PAL2 and PAL3. A C4H promoter region of 907 bp contained all of the three cis-acting elements (boxes P, A, and L) conserved among the PAL and 4CL genes so far reported as controlling expression.

Amino Acid Sequence↗
PubMed1998

A model for signal transduction during gamete release in the fucoid alga pelvetia compressa

Fucoid algae release gametes into seawater following an inductive light period (potentiation), and gamete expulsion from potentiated receptacles of Pelvetia compressa began about 2 min after a light-to-dark transition. Agitation of the medium reversed potentiation, with an exponential time course completed in about 3 h. Light regulated two signaling pathways during potentiation and gamete expulsion: a photosynthetic pathway and a photosynthesis-independent pathway in which red light was active but blue light was not. Uptake of K+ appears to have an important role in potentiation, because a 50% inhibition of potentiation occurred in the presence of the tetraethylammonium ion, a K+-channel blocker. A central role of anion channels in the maintenance of potentiation is suggested by the premature release of gametes in the light when receptacles were incubated with inhibitors of slow-type anion channels. An inhibitor of tyrosine kinases, tyrphostin A63, also inhibited potentiation. A model for gamete release from P. compressa is presented that proposes that illumination results in the accumulation of ions (e.g. K+) throughout the cells of the receptacle during potentiation, which then move into the extracellular matrix during gamete expulsion to generate osmomechanical force, resulting in gamete release.

Journal Article↗
PubMed1967

Chlorophyll Formation and Photosynthetic Competence in Euglena During Light-Induced Chloroplast Development in the Presence of 3, (3,4-dichlorophenyl) 1,1-Dimethyl Urea (DCMU).

The possibility that photosynthetic competence is gratuitous for light-induced chloroplast development in Euglena gracilis var. bacillaris was examined by incubating dark-grown resting cells in the light with DCMU, an inhibitor of photosynthesis. Under these conditions photosynthetic carbon dioxide fixation was inhibited essentially completely at all times during chloroplast development, but about 70% of the chlorophyll was formed with essentially the same pattern of accumulation found for cells incubated in the absence of the inhibitor. Electron microscopy of cells incubated with DCMU in the light revealed the formation of morphologically recognizable chloroplasts having comparable overall dimensions and structural elements to those found in normally developed chloroplasts, but frequently lacking a readily detectable pyrenoid with paramylum sheaths, and often containing increased numbers of discs per lamella. Such abnormalities are considered minor since upon removal of DCMU by centrifugation, the cells usually regained almost full photosynthetic competence on a chlorophyll basis.It is concluded that photosynthetic competence is not necessary for chloroplast development in Euglena and supports the hypothesis, already suggested from other evidence, that light induction results in activation of synthetic machinery external to the developing chloroplast.

Journal Article↗
PubMed1971

An Analysis of Phytochrome-mediated Anthocyanin Synthesis.

Phytochrome (far red form) alone can mediate anthocyanin synthesis in the mustard seedling (Sinapis alba L.). Complete photoreversibility and reciprocity, for both red and far red light exposures over a period of at least 5 minutes, demonstrate this phytochrome involvement.The duration of the initial lag-phase is constant (about 3 hours at 25 C) for seedlings more than 30 hours old and is specific for the system, being independent of the dose or quality of light. Since a complete reversal by far red of a red light induction is possible only during a 5 minute period, phytochrome (far red form) obviously mediates anthocyanin synthesis during the lag-phase although the actual synthesis of pigment can proceed only after the lag-phase is overcome. We suggest that phytochrome (far red form) exerts a double function during the initial lag-phase. It mediates both the build up of a biosynthetic potential ("capacity") and anthocyanin synthesis. However, the sequence of events leading to anthocyanin is arrested at some intermediate stage until this "capacity" is built up after 3 hours. Once "capacity" is achieved it does not decay readily. Therefore, no significant "secondary lag-phase" occurs if the seedling, under appropriate conditions, is reirradiated after an intervening dark period. The rate or extent of synthesis for both anthocyanin and lipoxygenase, previously reported (32), are functions of the amount of phytochrome (far red form). No "phytochrome paradoxes," i.e., nonrational relationships between the amount of phytochrome (far red form) and rate or extent of response, were detected. This fact suggests that the mustard seedling is especially well suited for investigating the biophysical and molecular mechanisms of phytochrome action.

Journal Article↗
PubMed1981

Photoregulation of the Carotenoid Biosynthetic Pathway in Albino and White Collar Mutants of Neurospora crassa.

The conversion of isopentenyl pyrophosphate to phytoene in Neurospora crassa requires both a soluble and a particulate fraction. Soluble and particulate enzyme fractions obtained from light-treated and dark-grown wild type, albino-1, albino-2, albino-3, and white collar-1 strains were mixed in various combinations, and the activity for conversion of [1-(14)C]isopentenyl pyrophosphate to phytoene was assayed. From such experiments it can be concluded that: (a) albino-3 is defective in the soluble fraction; (b) albino-2 is defective in the particulate fraction; (c) the in vivo light treatment increases the enzyme activity in the particulate fraction; (d) this light effect occurs in wild type, albino-1, and albino-3 strains; and (e) enzyme activity is present in the particulate fraction obtained from the white collar-1 mutant, but the in vivo light treatment does not cause an increase in this activity. To measure directly the level of particulate enzyme activity, [(14)C]geranylgeranyl pyrophosphate was used as a substrate. This compound, which is not available commercially, was synthesized enzymically using extracts of pea cotyledons. Particulate enzyme fractions obtained from wild type, albino-1, and albino-3 strains incorporate [(14)C]geranylgeranyl pyrophosphate into phytoene, and this activity is higher in extracts obtained from light-treated cultures. The particulate fraction obtained from the white collar-1 mutant also incorporates [(14)C]geranylgeranyl pyrophosphate into phytoene, but the in vivo light treatment does not cause an increase in this activity. No incorporation occurs when particulate fractions obtained from either dark-grown or light-treated albino-2 cultures are assayed. The soluble enzyme fraction obtained from the albino-3 mutant was shown to be almost totally defective in enzyme activity required for the biosynthesis of [(14)C]geranylgeranyl pyrophosphate from [1-(14)C]isopentenyl pyrophosphate. An in vivo light treatment increases the level of this activity in wild type, albino-1, albino-2, and albino-3 strains, but not in the white collar-1 mutant. A model is presented to account for all of the results obtained in this investigation. It is proposed that the white collar-1 strain is a regulatory mutant blocked in the light induction process, whereas the albino-1, albino-2, and albino-3 strains are each defective for a different enzyme in the carotenoid biosynthetic pathway.

Journal Article↗
PubMed1988

Nuclear-Cytoplasmic Partitioning of Phytochrome-Regulated Transcripts in Pisum sativum.

Nuclear and cytoplasmic mRNAs for several phytochrome-regulated genes were examined in Pisum seedlings in order to investigate possible light effects on mRNA partitioning between the nucleus and cytoplasm. Transcripts from each of five light-regulated genes exhibited different responses to a variety of light treatments, but for each transcript we observed a characteristic linear relationship between nuclear and cytoplasmic levels over a wide range of total transcript abundance. Different mRNAs are characterized by different nuclear-cytoplasmic ;partitioning coefficients', indicating that post-transcriptional events play a significant role in regulating the accumulation of these mRNAs during light induction.

Journal Article↗