Biomedical subjects

F M van der Lee

Publications and source records attributed to F M van der Lee.

8 recordsLinked to original sources

PubMed2000

The HIC signalling pathway links CO2 perception to stomatal development.

Stomatal pores on the leaf surface control both the uptake of CO2 for photosynthesis and the loss of water during transpiration. Since the industrial revolution, decreases in stomatal numbers in parallel with increases in atmospheric CO2 concentration have provided evidence of plant responses to changes in CO2 levels caused by human activity. This inverse correlation between stomatal density and CO2 concentration also holds for fossil material from the past 400 million years and has provided clues to the causes of global extinction events. Here we report the identification of the Arabidopsis gene HIC (for high carbon dioxide), which encodes a negative regulator of stomatal development that responds to CO2 concentration. This gene encodes a putative 3-keto acyl coenzyme A synthase--an enzyme involved in the synthesis of very-long-chain fatty acids. Mutant hic plants exhibit up to a 42% increase in stomatal density in response to a doubling of CO2. Our results identify a gene involved in the signal transduction pathway responsible for controlling stomatal numbers at elevated CO2.

Algal Proteins↗

PubMed1997

Regulatory sequences of Arabidopsis drive reporter gene expression in nematode feeding structures.

In the quest for plant regulatory sequences capable of driving nematode-triggered effector gene expression in feeding structures, we show that promoter tagging is a valuable tool. A large collection of transgenic Arabidopsis plants was generated. They were transformed with a beta-glucuronidase gene functioning as a promoter tag. Three T-DNA constructs, pGV1047, p delta gusBin19, and pMOG553, were used. Early responses to nematode invasion were of primary interest. Six lines exhibiting beta-glucuronidase activity in syncytia induced by the beet cyst nematode were studied. Reporter gene activation was also identified in galls induced by root knot and ectoparasitic nematodes. Time-course studies revealed that all six tags were differentially activated during the development of the feeding structure. T-DNA-flanking regions responsible for the observed responses after nematode infection were isolated and characterized for promoter activity.

Animals↗

PubMed1993

Differential expression of the human, mouse and rat IGF-II genes.

The IGF-II gene is a complex transcription unit. Multiple transcripts are synthesized as a result of alternate promoter usage and the splicing of unique 5' untranslated regions to common coding exons. In order to characterize the mechanisms of IGF-II gene regulation we performed comparative studies to define essential features of IGF-II expression in human, rat and mouse. Homologous promoter regions of the human, mouse and rat IGF-II genes were fused to the luciferase reporter gene and expression was measured in various cell lines that have an endogenously active or inactive IGF-II gene expression pattern, respectively. The transient promoter activity of the human, mouse and rat IGF-II constructs was further compared with the endogenous activity of the IGF-II gene in various tissues and cell lines of human, mouse and rat origin. The results indicate that in transient expression assays employing heterologous systems (e.g., mouse promoter in human cells), most IGF-II promoter constructs are active, albeit at low levels. Maximal promoter activity is only observed, however, in homologous systems (e.g., human promoter constructs tested in human cells). This suggests that each promoter, despite the strong sequence conservation of the homologous human, rat and mouse promoters, is adapted to the levels of the transcription factors present in its natural environment. Finally, IGF-II gene expression is not only regulated at the level of transcription but also depends on mRNA stability. We show that human, rat and also mouse IGF-II mRNAs are subjected to specific endonucleolytic cleavage, suggesting that specific cleavage of IGF-II mRNAs must be of general physiological importance.

Aging↗

PubMed1993

Differential gene expression in nematode-induced feeding structures of transgenic plants harbouring promoter-gusA fusion constructs.

Sedentary plant-parasitic nematodes are able to induce specialized feeding structures in the root system of their host plants by triggering a series of dramatic cellular responses. These changes presumably are accompanied by a reprogramming of gene expression. To monitor such changes, a variety of promoter-gusA fusion constructs were introduced into Arabidopsis and tobacco. Transgenic plants were analysed histochemically for GUS activity in the nematode feeding structures after infection with either Heterodera schachtii or Meloidogyne incognita. Promoters of the Cauliflower Mosaic Virus 35S gene, the bacterial nopaline synthase, rooting loci (rol) and T-cyt genes and the plant-derived phenylalanine ammonia-lyase I gene, which are highly active in non-infected roots, were all downregulated in the feeding structures as indicated by the strong decrease of GUS activity inside these structures. Less stringent downregulation was observed with chimeric gusA fusion constructs harbouring truncated rolB and rolC promoter sequences. Similar observations were made with transgenic Arabidopsis lines that carried randomly integrated promoterless gusA constructs to identify regulatory sequences in the plant genome. Most of the lines that were selected for expression in the root vascular cylinder demonstrated local downregulation in feeding structures after infection with H. schachtii. The reverse pattern of GUS activity, a blue feeding structure amidst unstained root cells, was also found in several lines. However, GUS activity that was entirely specific for the feeding structures was not observed. Our data show that the expression of a large number of genes is influenced during the development of the nematode feeding structures.

Animals↗

PubMed1993

Analysis of the adenovirus type 5 terminal protein precursor and DNA polymerase by linker insertion mutagenesis.

A series of adenovirus type 5 precursor terminal protein (pTP) and DNA polymerase (Ad pol) genes with linker insertion mutations were separately introduced into the vaccinia virus genome under the control of a late vaccinia virus promoter. The recombinant viruses were used for overexpression of the mutant genes in HeLa cells. In total, 22 different mutant pTP and 10 different Ad pol vaccinia virus recombinants were constructed, including some that expressed carboxyl-terminus-truncated forms of both proteins and one that produced the mutant H5ts149 Ad pol. To investigate the structure-function relationships of both proteins, extracts from cells infected with the recombinant viruses were tested for in vitro complementation of the initiation and elongation steps in adenovirus DNA replication. The results were in accordance with those of earlier in vivo experiments with these insertion mutants and indicate that multiple regions of both proteins are essential for adenovirus DNA replication. The carboxyl termini of both pTP and Ad pol were shown to be essential for proper functioning of these proteins during initiation of adenovirus DNA replication. Three different DNA replication-negative pTP mutants were shown to have residual activity in the initiation assay, suggesting not only that pTP is required for initiation but also that it may play a role in DNA replication after the deoxycytidylation step.

Adenoviridae↗

PubMed1990

Identification and initial characterization of a fourth leader exon and promoter of the human IGF-II gene.

Transcription of the human insulin-like growth factor II (IGF-II) gene is regulated by activation of multiple promoters which act in a tissue-specific and development-dependent manner. Previously, we have identified three different promoters, one of which is active in adult liver tissue only, whereas the other two are active in many fetal tissues and adult non-hepatic tissues. Here we report the identification of a fourth leader exon of the human IGF-II gene indicating the presence of a fourth promoter. Transcription from this promoter yields a 5.0 kb IGF-II mRNA species, which is detected in fetal liver and leiomyosarcoma tissue.

Animals↗

PubMed1988

The binding of in vitro synthesized adenovirus DNA binding protein to single-stranded DNA is stimulated by zinc ions.

We have synthesized wild type DNA binding protein (DBP) of adenovirus type 5 (Ad5) and several truncated forms of this protein by a combination of in vitro transcription and translation. The proteins obtained were tested for binding to a single-stranded DNA-cellulose column. It could be shown that for binding of in vitro synthesized wild type DBP, it is necessary to add zinc ions to the in vitro translation system. Binding studies with the truncated proteins revealed that deletion of the carboxyl-terminal 46 amino acids abolishes DNA binding.

Adenoviruses, Human↗

PubMed1988

The genes encoding the DNA binding protein and the 23K protease of adenovirus types 40 and 41.

The adenovirus (Ad) single-stranded DNA binding protein (DBP) is a multifunctional protein. It is thought to consist of two domains, the amino-terminal domain involved in host-range determination and the carboxyl-terminal domain functioning in DNA replication and DNA binding. We have determined the nucleotide sequences of the DBP genes of Ad40 and Ad41, two human adenoviral serotypes that differ significantly from other adenoviruses. Regions of structural and functional importance in the corresponding proteins could be identified by comparison of the amino acid sequences with those of other known DBPs. In addition, the nucleotide sequences of the DBP early promoters, of the 23K protease genes, and of parts of the hexon and 100K protein genes have been determined. It can be deduced from the nucleotide sequences, that the Ad40 and Ad41 DBPs are relatively small (473 and 474 amino acids (a.a.), respectively, versus 529 a.a. for the Ad5 DBP). This is caused by the presence of very small amino-terminal domains of 119 a.a. (Ad40) and 120 a.a. (Ad41), as compared to 173 a.a. for the corresponding Ad5 domain. Only a few amino acids in this domain have been conserved in all known DBPs. The carboxyl-terminal domains show a higher degree of sequence conservation. In this domain, four strongly conserved regions can be identified, one of which might form a metal-binding site. The 23K proteases of both Ad40 and Ad41 show a strong homology to the Ad2 and Ad5 proteins, with the exception of the carboxyl-terminal end of the proteins. The 23K protease gene of Ad41 has an open reading frame that extends beyond the polyadenylation signal, in contrast to the Ad40 gene that ends well in front of the signal.

Adenoviruses, Human↗