Receptor-like protein kinase genes of Arabidopsis thaliana

The isolation of a maize cDNA clone that encodes a membrane spanning protein kinase related to the self-incompatibility glycoproteins (SLG) of Brassica and structurally similar to the growth factor receptor tyrosine kinases has recently been reported. Three distinct receptor-like protein kinase (RLK) cDNA clones from Arabidopsis thaliana have now been identified. Two of the Arabidopsis RLK genes encode SLG-related protein kinases but have different patterns of expression: one is expressed predominantly in rosettes while the other is expressed primarily in roots. The third RLK gene contains an extracellular domain that consists of 21 leucine-rich repeats that are analogous to the leucine-rich repeats found in proteins from humans, flies and yeast. The Arabidopsis leucine-rich gene is expressed at equivalent levels in roots and rosettes. These results show that there are several genes in higher plants that encode members of the receptor protein kinase superfamily. The structural diversity and differential expression of these genes suggest that each plays a distinct and possibly important role in cellular signaling in plants.     

A probarley lectin processing enzyme purified from Arabidopsis thaliana seeds

An aspartic proteinase was purified from the seeds of Arabidopsis thaliana (ecotype RLD) using affinity chromatography on pepstatin-agarose and ion exchange chromatography. The purified enzyme is optimally active at pH 3.5 and completely inhibited by pepstatin A. The purified Arabidopsis aspartic proteinase contains four subunits (apparent molecular weights 31, 28.5, 15 and 6 kDa), two of which are probably linked by disulfide bridges. These properties are similar to the aspartic proteinase previously isolated from barley seeds. The amino acid sequence of the peptide subunits corresponds exactly with the sequence of the previously isolated cDNA for the Arabidopsis aspartic proteinase. The Arabidopsis enzyme processed probarley lectin in vitro at the carboxy-terminus between phenylalanine and alanine, the same place where the barley enzyme cleaves the lectin in vitro. The aspartic proteinase appears to be the major enzyme processing the lectin in seeds as pepstatin A inhibited this activity in a crude seed extract.     

Inflorescence-specific genes from Arabidopsis thaliana encoding glycine-rich proteins

Genomic and cDNA clones for three inflorescence-specific genes from Arabidopsis thaliana were isolated and characterized. The genes are tandemly organized in the genome on a 10 kb fragment. The expression of these genes is coordinately regulated in a developmental and organ-specific pattern. They are expressed predominantly in anthers at the later stage of flower development. The primary structure of the encoded gene products exhibits comparable features consisting of a hydrophobic domain at the N-terminal region followed by repeated glycine-rich motifs. Little homology is observed either between the glycine-rich domain of the three genes or with previously described glycine-rich proteins from other plant species.     

Chromosomal mapping of genes in the RBCS family in Arabidopsis thaliana

We evaluated the usefulness of magnetic resonance angiography (MRA) for showing the topography of paraclinoid carotid artery aneurysms in 27 patients with 30 paraclinoid aneurysms undergoing conventional angiography, three-dimensional time-of-flight MRA and surgery. The anatomy shown on the axial MRA source images was consistent with that found at surgery. The neck of the aneurysm could always be identified on the source images, while it could not be analysed exactly on conventional angiography in 3 cases (10%). The optic nerves, including those displaced by the aneurysm, were recognised in all patients. The anterior clinoid process was shown as a low-intensity rim or area contiguous with the cortical bone. The source images were of great value in understanding the topography of paraclinoid carotid artery aneurysms.     

Genetic effects of lead nitrate on seeds of chronically irradiated populations of Arabidopsis thaliana

The genetic effects of simultaneous treatment of Arabidopsis seeds by the sodium lead and low doses of chronic irradiation was studied. It was found that the sodium lead is not strongly mutagen and has more toxic effect on biological systems. The high lead toxicity is a possible reason of synergetic effects of combined treatment with irradiation rays.     

Multiple phytochromes are involved in red-light-induced enhancement of first-positive phototropism in Arabidopsis thaliana

Microsatellite instability (MSI), a symptom of defect in DNA mismatch repair function, represents a type of genomic instability frequently detected in many types of cancers. However, the involvement of MSI in non-Hodgkin's lymphomas (NHL) has not been conclusively investigated. In this study, we have tested the presence of MSI in 69 cases of B-cell NHL (B-NHL) representative of the various histologic categories of the disease and including 17 cases of acquired immunodeficiency syndrome (AIDS)-related B-NHL (AIDS-NHL). In addition, for selected B-NHL cases, consecutive samples obtained before and after clinical progression (with and without concomitant histologic transformation) were also investigated. Five distinct microsatellite repeats (2 dinucleotide, 2 trinucleotide, and 1 tetranucleotide repeats) were analyzed by polymerase chain reaction in all cases. MSI, defined by the presence of microsatellite alterations in two or more of the five microsatellite loci tested, was not found in NHL. In contrast to a previous study reporting the frequent association between MSI and AIDS-NHL, we found this abnormality in only 1 of 17 cases of AIDS-NHL representative of the major subtypes. Overall, these data indicate that defects in DNA mismatch repair do not contribute significantly to the molecular pathogenesis of B-NHL.     

Ethylene responses are negatively regulated by a receptor gene family in Arabidopsis thaliana

Disseminated neuroblastoma frequently show a very poor prognosis. N-myc gene amplification, 1p deletion and lack of CD44 gene expression, are all genetic factors associated with the disease's dissemination. Human neuroblastoma xenografts in nude mice has permitted to characterize, in disseminated neuroblasts, oncogenes overexpression, inactivation of tumor suppressor genes as well as detoxifying genes activation which contributes to increase cellular resistance to chemotherapy. These genetic abnormalities permit to propose a nosology of this very aggressive pediatric solid tumor. Hopefully, this genetic classification could be of great value for new therapeutic approaches.     

The prostaglandin E2 and F2 alpha receptor genes are expressed in human myometrium and are down-regulated during pregnancy

Prostaglandin (PG) E2 and PGF2 alpha are believed to play important roles in the myometrial contraction and the initiation of labor. Myometrial contraction by these prostanoids is mediated mainly through EP3 and FP, which are specific receptors to PGE2 and PGF2 alpha, respectively. During normal pregnancy, uterine myometrium are relaxed until term. To explore the involvement of EP3 and FP in the myometrial relaxation during pregnancy, we examined the EP3 and FP gene expressions in nonpregnant and pregnant myometrium obtained by hysterectomy for gynecological diseases. In all samples examined, expressions of EP3 and FP genes were detected. During pregnancy, the expression of EP3 gene in human myometrium was significantly reduced, to 60% of that in nonpregnant myometrium. The expression of FP gene in human myometrium also decreased during pregnancy to 55% of that in nonpregnant myometrium. In the myometrium from the nonpregnant women taking combined oral contraceptives, the gene expressions of EP3 and FP were not significantly changed as compared to those in nonpregnant controls. The down-regulation of EP3 and FP during pregnancy may play a role in the relaxation of myometrium and thus in the maintenance of normal pregnancy in humans.     

Two Arabidopsis thaliana carotene desaturases, phytoene desaturase and zeta-carotene desaturase, expressed in Escherichia coli, catalyze a poly-cis pathway to yield pro-lycopene

We have expressed in Escerichia coli the enzymes geranylgeranyl diphosphate synthase and phytoene synthase, from the soil bacterium Erwinia stewartii, and the two carotene desaturases phytoene desaturase and carotene zeta-carotene desaturase from Arabidopsis thaliana. We show that pro-lycopene (7,9,7',9'-tetra-cis)-lycopene is the main end product of the plant desaturation pathway in these cells. In addition, light is required in this system. Whereas in the dark mainly zeta-carotene, the phytoene desaturase product, accumulates, illumination leads to activation of this intermediate caused by its photoisomerization. zeta-Carotene then meets the stereospecific requirements of zeta-carotene desaturase and pro-lycopene is formed. In contrast, a strain of E. coli carrying geranylgeranyl diphosphate synthase, phytoene desaturase and the bacterial carotene desaturase CrtI, which mediates lycopene formation from phytoene, does not require light, nor is a poly-cis-lycopene species formed. The stereoselectivity of the plant-type desaturation pathway expressed in E. coli is the same as previously shown with chromoplast membranes. As the phytoene desaturase and zeta-carotene desaturase used originate from a system not capable of developing chromoplasts, this indicates that the poly-cis pathway of carotene desaturation may have a wider occurrence than initially believed.     

Two different genes encode ferrochelatase in Arabidopsis: mapping, expression and subcellular targeting of the precursor proteins

Six adolescents, five males with prolactin-secreting pituitary macroadenomas and one female with idiopathic hyperprolactinaemia, are described. Their ages at presentation ranged from 13 years 7 months to 16 years 6 months. Presenting symptoms included headache, visual field defect, arrested growth and puberty. Only two cases had galactorrhoea. Every case had an elevated serum prolactin level. Three had surgery before the results of serum prolactin were to hand. Each patient was treated with bromocriptine. Bromocriptine suppressed serum prolactin level to normal in four cases, but in the girl with idiopathic hyperprolactinaemia, bromocriptine was not useful. In two boys, serum prolactin was not suppressed with bromocriptine therapy alone, and they were subsequently treated with cabergoline, surgery and irradiation. Nevertheless, in children and adolescents with prolactin-secreting pituitary adenoma, bromocriptine should be the first line of treatment.     

Fertilization-independent seed development in Arabidopsis thaliana

We report mutants in Arabidopsis thaliana (fertilization-independent seed:fis) in which certain processes of seed development are uncoupled from the double fertilization event that occurs after pollination. These mutants were isolated as ethyl methanesulfonate-induced pseudo-revertants of the pistillata phenotype. Although the pistillata (pi) mutant has short siliques devoid of seed, the fis mutants in the pi background have long siliques containing developing seeds, even though the flowers remain free of pollen. The three fis mutations map to loci on three different chromosomes. In fis1 and fis2 seeds, the autonomous endosperm nuclei are diploid and the endosperm develops to the point of cellularization; the partially developed seeds then atrophy. In these two mutants, proembryos are formed in a low proportion of seeds and do not develop beyond the globular stage. When FIS/fis plants are pollinated by pollen from FIS/FIS plants, approximately 50% of the resulting seeds contain fully developed embryos; these seeds germinate and form viable seedlings (FIS/FIS). The other 50% of seeds shrivel and do not germinate; they contain embryos arrested at the torpedo stage (FIS/fis). In normal sexual reproduction, the products of the FIS genes are likely to play important regulatory roles in the development of seed after fertilization.     

GATA-1 and erythropoietin receptor genes are highly expressed in erythroleukemia

BACKGROUND: The differential diagnosis of eosinophilic gastroenteritis (EG) includes, among other diseases, parasitic infections such as anisakiasis, which has acquired worldwide importance. METHODS: We reviewed all patients referred to our allergy service who had been diagnosed as having primary EG to determine the possible role of Anisakis simplex in the etiopathology of the disease. All patients (n = 10) were studied and diagnosed as having primary EG between 1989 and 1996, inclusive. Two different groups of subjects were used as controls: group A (149 subjects without digestive disorder) and group B (10 subjects with digestive disorder different from EG). Cutaneous prick tests were performed with the main foods, aeroallergens, and commercial extract of A. simplex. Total and specific serum IgE was measured in all patients. Gastric or gut histologic specimens were re-examined in five cases. RESULTS: Peripheral eosinophilia was detected in 40% of the patients with EG, and sensitization to A. simplex was detected in 80% of these. In both control groups, the rate of sensitization to A. simplex was 10%. Sensitization to A. simplex in EG patients with respect to control groups A and B showed odds ratios (OR) of 36 and 40, respectively. In one case, serialization of the histologic section allowed us to observe a whole Anisakis larva. CONCLUSIONS: Immunologic methods to detect specific antibodies against Anisakis should be used routinely before diagnosing EG as primary disorder. Preventive measures are of capital importance.     

Identification of novel genes that are differentially expressed in human colorectal carcinoma

To investigate the origin of fragile X mutations in the Argentine population, we studied the alleles and haplotypes at DXS548 and FRAXAC1 loci of 42 unrelated fragile X chromosomes and 168 normal ones. Four haplotypes presented in linkage disequilibrium and accounted for 76.2% of fragile X chromosomes, representing the high frequency of haplotype DXS548-FRAXAC1 7-1 (26.2%) characteristic of our population. FRAXAC1 allele 1 was observed on 47.6% of fragile X chromosomes. Thus, we provide evidence for fragile X founder effects in the Argentine population, similar to those observed in Caucasians and in Asians.     

Herbicide safener-inducible gene expression in Arabidopsis thaliana

The potential use of a new chemical-inducible gene expression system in Arabidopsis thaliana has been examined. The system is based on the maize In2-2 promoter which is activated by benzenesulfonamide herbicide safeners. Plants transformed with the beta-glucuronidase (gus) reporter gene under the control of the In2-2 promoter were grown in the presence of different safeners and the induced GUS activity pattern was studied histochemically. In the absence of safeners, the In2-2 promoter was not active. Application of different safeners induced distinct gus expression patterns, including expression in the root, hydathodes, and the shoot apical meristem. Plants maintained continuously on inducing concentrations of the safeners were retarded in growth. The growth inhibition effects of the Sa5 safener could be overcome in a sulfonylurea-resistant background. In2-2 promoter activity could also be induced by the sulfonylurea herbicide chlorsulfuron. In the sulfonylurea-resistant background, which derives from herbicide-resistant acetolactate synthase activity, induction of the In2-2 promoter by chlorsulfuron was lower. Furthermore, branched-chain amino acids, known to inhibit acetolactate synthase activity, also induced In2-2 promoter activity. Our data suggest a strong correlation between In2-2 expression and inhibition of the acetolactate synthase activity.     

Arabidopsis thaliana mutants altered in homologous recombination

Homologous recombination contributes both to the generation of allelic diversity and to the preservation of genetic information. In plants, a lack of suitable experimental material has prevented studies of the regulatory and enzymatic aspects of recombination in somatic and meiotic cells. We have isolated nine Arabidopsis thaliana mutants hypersensitive to x-ray irradiation (xrs) and examined their recombination properties. For the three xrs loci described here, single recessive mutations were found to confer simultaneous hypersensitivities to the DNA-damaging chemicals mitomycin C (MMCs) and/or methyl methanesulfonate (MMSs) and alterations in homologous recombination. Mutant xrs9 (Xrays, MMSs) is reduced in both somatic and meiotic recombination and resembles yeast mutants of the rad52 epistatic group. xrs11 (Xrays, MMCs) is deficient in the x-ray-mediated stimulation of homologous recombination in somatic cells in a manner suggesting a specific signaling defect. xrs4 (Xrays, MMSs, MMCs) has a significant deficiency in somatic recombination, but this is accompanied by meiotic hyper-recombination. A corresponding phenotype has not been reported in other systems and thus this indicates a novel, plant-specific regulatory circuit linking mitotic and meiotic recombination.