Stress-responsive expression of genes for two-component response regulator-like proteins in Arabidopsis thaliana

Four cDNAs that encode two-component response regulator-like proteins were cloned from Arabidopsis thaliana. Putative proteins (ATRR1-4) contain a receiver domain with a conserved aspartate residue - a possible phosphorylation site - at the N-terminal half. ATRR2 lacks the C-terminal half; the others contain a C-terminal domain abundant in acidic amino acids or proline residues. ATRR1 and ATRR2 are expressed more in roots than in other tissues and are induced by low temperature, dehydration and high salinity. Levels of ATRR3 and ATRR4 were not affected by stress treatments. These results suggest that ATRRs play distinct physiological roles in Arabidopsis, and that some are involved in stress responses.

The presenilin 2 loop domain interacts with the mu-calpain C-terminal region

Presenilin 2 (PS2) is a gene responsible for the early-onset familial Alzheimer's disease (AD). PS2 mutations are considered to be closely related to the pathogenesis of AD. We screened for proteins that interact with PS2 to understand its pathological and physiological functions. Using the PS2 loop domain as the bait, the yeast two-hybrid system was used for screening, and mu-calpain was identified as a PS2 binding protein. In COS-1 cells, the interaction of PS2 with mu-calpain was confirmed by immunoprecipitation. These results suggested that PS2 and mu-calpain interact with each other, and might regulate each other's functions.

ERD6, a cDNA clone for an early dehydration-induced gene of Arabidopsis, encodes a putative sugar transporter

Previously, we constructed a cDNA library from Arabidopsis plants that were exposed to dehydration stress for 1 h and obtained the ERD6 clone. Here we report that the ERD6 cDNA consists of 1741 bp and encodes a polypeptide of 496 amino acids having a predicted molecular weight of 54,354. The putative polypeptide of ERD6 is related to those of sugar transporters of bacteria, yeasts, plants and mammals. Hydropathy analysis revealed that ERD6 protein has 12 putative transmembrane domains and a central hydrophilic region. Sequences that are conserved at the ends of the 6th and 12th membrane-spanning domains of sugar transporters are also present in ERD6. These data suggest that ERD6 encodes a sugar transporter. Genomic Southern blots indicate that the ERD6 gene is a member of a multigene family in the Arabidopsis genome. The expression of the ERD6 gene was induced not only by dehydration but also by cold treatment.

Increased tau protein level in postmortem cerebrospinal fluid

Microtubule-associated protein tau has been reported to be significantly increased in cerebrospinal fluid (CSF) of the patients with Alzheimer's disease (AD), which suggests that it is possibly a biological marker for the diagnosis of AD. The underlying mechanism of the increased tau level in CSF, however, is not known. In this study, the tau levels were compared between antemortem and postmortem CSF. The postmortem tau levels in CSF were significantly increased in all groups including AD, neurological control, and nondemented control. A striking elevation of CSF tau was observed during the postmortem change with the nondemented subjects. These findings may offer some insight into the understanding of the mechanism of the increased tau level in CSF with AD and other related disorders.

The efficacy of immunochemotherapy with strontium (Sr) in the 1,2-dimethylhydrazine (DMH) induced rat carcinogenetic model: ultrastructural characteristics of the mitochondria in the liver

It is said that stable strontium (Sr), which exists naturally in living cells as a microelement, has cytoprotective effects on liver cells in mammals. We attempted to examine the cytoprotective and anticancer effects of Sr using the rat carcinogenetic model induced by DMH (1,2-dimethylhydrazine). In a comparison of animals given UFT, PSK and Sr or UFT and PSK, carcinogenes in the colon and also increases in immunosuppressive acidic protein (IAP) levels were suppressed. Electron microscopic observation in the Sr group revealed a tendency toward stabilization of the mitochondrial membrane and highly developed rough endoplasmic reticulum in both the right and left lobe. This tendency became more obvious as the duration of oral intake of Sr was prolonged. Our study suggest that the cytoprotective effect of Sr on mitochondria in the liver may suppress carcinogenesis.

Survey of human group C rotaviruses in Japan during the winter of 1992 to 1993

Fecal specimens from patients with acute diarrhea were collected from 10 prefectures in Japan over a 6-month period (November 1992 to April 1993), and the specimens that were negative for human group A rotaviruses were screened for the presence of human group C rotaviruses (CHRVs) by the reverse passive hemagglutination test. Of 784 specimens examined, 53 samples (6.8%) that were collected in 7 of 10 prefectures were positive for CHRV, indicating that CHRVs are widely distributed across Japan. Most of the CHRV isolates were detected in March and April, and CHRVs mainly prevailed in children ages 3 to 8 years. The genome electropherotypes of eight strains isolated in five individual prefectures were surprisingly similar to each other and were different from those of CHRV strains isolated to date. The outer capsid glycoprotein (VP7) gene homologies of the isolates retrieved in 1993 were subsequently analyzed by the dot blot hybridization method. As a result, the VP7 genes of the isolates revealed very high levels of homology not only with each other but also with the VP7 gene of the OK118 strain isolated in 1988. These results suggest that a large-scale outbreak of CHRV occurred during the winter of 1992 and 1993 in Japan.

A novel brain gene, norbin, induced by treatment of tetraethylammonium in rat hippocampal slice and accompanied with neurite-outgrowth in neuro 2a cells

Tetraethylammonium (TEA) induces long-term potentiation (LTP)-like synaptic enhancement in rat hippocampal slices. To find the genes related to this phenomenon, subtraction screening was performed between the mRNA of TEA-treated slices and that of untreated whole brain. One of the clones induced by the TEA treatment, named as norbin, was expressed only in neural tissues. The predicted protein sequence of norbin consisted of 729 amino acids, and no homologies in the sequence were found with known genes or proteins. Overexpression of norbin in cultured Neuro 2a cells by cDNA transfection induced neurite-outgrowth. Since in the course of neural plasticity the formation of new synapses should occur, the neurite-outgrowth-related protein, norbin, might play an important role in neural plasticity.

Insulin resistance as an independent risk factor for carotid artery wall intima media thickening in vasospastic angina

Studies have shown the presence of insulin resistance together with compensatory hyperinsulinemia in vasospastic angina as well as obstructive coronary artery disease. There is growing evidence that the development of coronary atherosclerosis may be closely related to systemic atherosclerosis as well as coronary spasm. However, no information is available about the possible relationship between insulin resistance and the existence of carotid atherosclerosis in vasospastic angina without segmental stenosis or luminal irregularities in coronary angiograms. To evaluate the independent effect of insulin resistance on carotid intima media thickening, we performed insulin sensitivity tests (steady-state plasma glucose method) on 40 patients with vasospastic angina and 24 control subjects with angiographically intact coronary arteries. Both oral glucose tolerance tests and lipid analyses were performed. Using B-mode ultrasonography, we assessed intima media thickness and plaque formation of common carotid arteries in these subjects. The steady-state plasma glucose level in the vasospastic angina group was about twofold higher than that of the control group, confirming the presence of insulin resistance in patients with vasospastic angina. The patients with vasospastic angina showed a significant increase in the average intima media thickness of the carotid wall and frequency of plaque formation, although they were comparable to the control subjects in risk factors other than insulin resistance. The intima media thickness was correlated with age (r = .62, P < .001), 2-hour insulin area (r = .45, P < .01), and steady-state plasma glucose level (r = .68, P < .0001) in patients with vasospastic angina. Similar correlations were observed in the control subjects. Multiple regression analyses of data indicated that 67% of the variation in the intima media thickness could be accounted for by age, steady-state plasma glucose level, and cigarette-years in vasospastic angina. In addition, differences in IMT were independently related to vasospastic angina. These results suggest that insulin resistance in association with compensatory hyperinsulinemia may be an important pathogenic factor for the development of coronary artery spasms and systemic early atherosclerosis.

Molecular characterization of a cDNA encoding a novel small GTP-binding protein from Arabidopsis thaliana

A full-length cDNA clone encoding a novel Rab protein AtRab alpha of the monomeric small GTP-binding protein family has been isolated from Arabidopsis thaliana. AtRab alpha has 210 amino acids with a calculated molecular mass of 23.3 kDa. The highest homology was found to Rab1x and Rab1y from Lotus japonicus. Southern blot analysis of genomic DNA indicated that AtRab alpha was encoded by a single copy gene. Northern blot analysis showed that expression of the AtRab alpha mRNA was rich in stems and roots, but poor in leaves and flowers, which is different from the expression pattern of other Arabidopsis Rab genes.

Regulation of levels of proline as an osmolyte in plants under water stress

Compatible osmolytes are potent osmoprotectants that play a role in counteracting the effects of osmotic stress. Proline (Pro) is one of the most common compatible osmolytes in water-stressed plants. The accumulation of Pro in dehydrated plants is caused both by activation of the biosynthesis of Pro and by inactivation of the degradation of Pro. In plants, L-Pro is synthesized from L-glutamic acid (L-Glu) via delta(1)-pyrroline-5-carboxylate (P5C) by two enzymes, P5C synthetase (P5CS) and P5C reductase (P5CR). L-Pro is metabolized to L-Glu via P5C by two enzymes, proline dehydrogenase (oxidase) (ProDH; EC 1.5.99.8) and P5C dehydrogenase (P5CDH; EC 1.5.1.12). Such metabolism of Pro is inhibited when Pro accumulates during dehydration and it is activated when rehydration occurs. Under dehydration conditions, when expression of the gene for P5CS is strongly induced, expression of the gene for ProDH is inhibited. By contrast, under rehydration conditions, when the expression of the gene for ProDH is strongly induced, the expression of the gene for P5CS is inhibited. Thus, P5CS, which acts during the biosynthesis of Pro, and ProDH, which acts during the metabolism of Pro, appear to be the rate-limiting factors under water stress. Therefore, it is suggested that levels of Pro are regulated at the level of transcriptional the genes of these two enzymes during dehydration and rehydration. Moreover, it has been demonstrated that Pro acts as an osmoprotectant and that overproduction of Pro results in increased tolerance to osmotic stress of transgenic tobacco plants. Genetically engineered crop plants that overproduce Pro might, thus, acquire osmotolerance, namely, the ability to tolerate environmental stresses such as drought and high salinity.

Role of arabidopsis MYC and MYB homologs in drought- and abscisic acid-regulated gene expression

In Arabidopsis, the induction of a dehydration-responsive gene, rd22, is mediated by abscisic acid (ABA) and requires protein biosynthesis for ABA-dependent gene expression. Previous experiments established that a 67-bp DNA fragment of the rd22 promoter is sufficient for dehydration- and ABA-induced gene expression and that this DNA fragment contains two closely located putative recognition sites for the basic helix-loop-helix protein MYC and one putative recognition site for MYB. We have carefully analyzed the 67-bp region of the rd22 promoter in transgenic tobacco plants and found that both the first MYC site and the MYB recognition site function as cis-acting elements in the dehydration-induced expression of the rd22 gene. A cDNA encoding a MYC-related DNA binding protein was isolated by DNA-ligand binding screening, using the 67-bp region as a probe, and designated rd22BP1. The rd22BP1 cDNA encodes a 68-kD protein that has a typical DNA binding domain of a basic region helix-loop-helix leucine zipper motif in MYC-related transcription factors. The rd22BP1 protein binds specifically to the first MYC recognition site in the 67-bp fragment. RNA gel blot analysis revealed that transcription of the rd22BP1 gene is induced by dehydration stress and ABA treatment, and its induction precedes that of rd22. We have reported a drought- and ABA-inducible gene that encodes the MYB-related protein ATMYB2. In a transient transactivation experiment using Arabidopsis leaf protoplasts, we demonstrated that both the rd22BP1 and ATMYB2 proteins activate transcription of the rd22 promoter fused to the beta-glucuronidase reporter gene. These results indicate that both the rd22BP1 (MYC) and ATMYB2 (MYB) proteins function as transcriptional activators in the dehydration- and ABA-inducible expression of the rd22 gene.

Role of arabidopsis MYC and MYB homologs in drought- and abscisic acid-regulated gene expression

In Arabidopsis, the induction of a dehydration-responsive gene, rd22, is mediated by abscisic acid (ABA) and requires protein biosynthesis for ABA-dependent gene expression. Previous experiments established that a 67-bp DNA fragment of the rd22 promoter is sufficient for dehydration- and ABA-induced gene expression and that this DNA fragment contains two closely located putative recognition sites for the basic helix-loop-helix protein MYC and one putative recognition site for MYB. We have carefully analyzed the 67-bp region of the rd22 promoter in transgenic tobacco plants and found that both the first MYC site and the MYB recognition site function as cis-acting elements in the dehydration-induced expression of the rd22 gene. A cDNA encoding a MYC-related DNA binding protein was isolated by DNA-ligand binding screening, using the 67-bp region as a probe, and designated rd22BP1. The rd22BP1 cDNA encodes a 68-kD protein that has a typical DNA binding domain of a basic region helix-loop-helix leucine zipper motif in MYC-related transcription factors. The rd22BP1 protein binds specifically to the first MYC recognition site in the 67-bp fragment. RNA gel blot analysis revealed that transcription of the rd22BP1 gene is induced by dehydration stress and ABA treatment, and its induction precedes that of rd22. We have reported a drought- and ABA-inducible gene that encodes the MYB-related protein ATMYB2. In a transient transactivation experiment using Arabidopsis leaf protoplasts, we demonstrated that both the rd22BP1 and ATMYB2 proteins activate transcription of the rd22 promoter fused to the beta-glucuronidase reporter gene. These results indicate that both the rd22BP1 (MYC) and ATMYB2 (MYB) proteins function as transcriptional activators in the dehydration- and ABA-inducible expression of the rd22 gene.

A nuclear gene, erd1, encoding a chloroplast-targeted Clp protease regulatory subunit homolog is not only induced by water stress but also developmentally up-regulated during senescence in Arabidopsis thaliana

A cDNA, ERD1, isolated from one-hour-dehydrated plants of Arabidopsis thaliana L. encodes a putative protein that is similar to the regulatory ATPase subunit (ClpA) of the Clp protease and contains a putative chloroplast-targeting transit-peptide at the N-terminus. A chimeric gene with the putative plastid-targeting sequence of the erd1 gene fused to the synthetic green-fluorescent protein (sGFP) gene was constructed and introduced into Arabidopsis protoplasts. The N-terminal region of the ERD1 protein directed the sGFP protein into the plastids of the protoplasts, and functioned as a transit peptide. Northern blot analysis indicated that expression of the erd1 gene was induced not only by water stress, such as dehydration and high salinity, but also by natural senescence and dark-induced etiolation. The erd1 gene was not strongly induced by exogenous abscisic acid. A chimeric gene with the 0.9 kb promoter region of the erd1 gene fused to the beta-glucuronidase (GUS) reporter gene was constructed, and tobacco plants transformed with the construct. The GUS reporter gene driven by the erd1 promoter was induced by dehydration and high salt stress at significant levels in the transgenic plants. The GUS gene was strongly expressed in older leaves without dehydration, and was induced by dark-induced etiolation. Furthermore, GUS activity was reduced by cytokinin treatment during dark-induced etiolation. These results indicate that expression of the erd1 gene is developmentally up-regulated by senescence as well as by water stress.

Characterization of three cDNA species encoding plastid RNA polymerase sigma factors in Arabidopsis thaliana: evidence for the sigma factor heterogeneity in higher plant plastids

By database search analysis, we identified three Arabidopsis EST (Expression Sequence Tag) entries having similarity to eubacterial RNA polymerase sigma factors. cDNA clones corresponding to these partial sequences were isolated, and the complete nucleotide sequences were determined. All three sequences encode proteins highly homologous to cyanobacterial and plastid sigma factors, and the gene products have N-terminal extensions which are assumed to function as plastid-targeting transit peptides. Thus we have concluded that the gene products are RNA polymerase sigma factors of plastids, and named sigA, sigB and sigC, respectively. Expression of these genes was analyzed by RNA gel-blot analysis and shown to be induced by illumination after a short-term dark adaptation. This strongly suggests that light regulation of the nuclear encoded sigma factor genes is involved in light-dependent activation of plastid promoters.

Functional cloning of a cDNA encoding Mei2-like protein from Arabidopsis thaliana using a fission yeast pheromone receptor deficient mutant

To isolate Arabidopsis cDNAs that encode signal transducers and components involved in the regulation of meiosis, a trans-complementation analysis was performed using a Schizosaccharomyces pombe meiosis-defective mutant in which the genes for pheromone receptors were disabled. One cDNA obtained in this screening encodes a polypeptide, named AML1, that shows significant similarity to S. pombe Mei2 protein and has three putative RNA-recognition motifs like as Mei2. Mei2 is involved in the regulation of meiosis in fission yeast. Northern blot analysis showed that the AML1 gene is expressed in each organ. The possible functions of AML1 are discussed.

Rapid construction of a transcription map for a cosmid contig of Arabidopsis thaliana genome using a novel cDNA selection method

Significant progress has been made on the random sequencing of cDNAs (ESTs) and the genetic and physical mapping of the Arabidopsis thaliana genome. New techniques are now required to identify and map the expressed genes efficiently on A. thaliana chromosomes. A novel method to construct a transcription map of expressed genes or cDNAs in specific regions of the genome using DNA-latex particles has been developed. The region-specific DNA fragments prepared from six cosmid clones that constitute a contig covering the abi1 locus on chromosome 4 were covalently bound to latex particles. The DNA-latex particles were used for the selection of region-specific cDNAs. Sequence analysis of the cDNA clones revealed that ABI1, RPS2, casein kinase 1 (CK1), nucleosome assembly protein I (NAP) cDNAs and T20837 EST, which are situated within the contig near abi1 locus, were selected. These results indicate that the cDNAs in the specific region of the genome were faithfully selected with this method. Sequence analysis also indicated that 11 selected cDNAs were derived from novel genes located near the abi1 locus and that four of the selected cDNAs encode putative proteins that have sequence similarity to cationic peroxidase, phosphatidylserine decarboxylase 2 (PSD2), trans-caffeoyl CoA 3-O-methyltransferase (CCoAMT), and proteasome subunit XC3.

Sequence analysis of SRSV in fecal specimens from an epidemic of infantile gastroenteritis, October to December 1995, Japan

From October to December in 1995, an epidemic of infantile gastroenteritis occurred all over Japan except in Hokkaido and Okinawa prefectures. The number of infected infants and young children was estimated to be over 5 million cases [Editorial, IASR 1996]. The stool specimens from patients were examined for the presence of small round structured viruses (SRSVs) by reverse transcription-polymerase chain reaction (RT-PCR) and nucleotide sequencing of parts of the RNA-dependent RNA polymerase region. Thirty-five of 87 stool specimens examined gave positive results. Genomic variation was investigated by sequence analysis of a 327 bp cDNA region. The nucleotide and deduced amino acid sequences of the ten strains segregated into two distinct groups; one showed 96.0-100% nucleotide and 99.1-100% amino acid identity, the others showed 91.4-99.7% nucleotide and 93.5-100% identity. The main mechanism of transmission remains unknown. However, these data suggest the possibility of person-to-person spread by two or more kinds of SRSV.

Metabolism of the intravenously administered recombinant human basic fibroblast growth factor, trafermin, in liver and kidney: degradation implicated in its selective localization to the fenestrated type microvasculatures

The fate of trafermin (recombinant human basic fibroblast growth factor) was examined after intravenous administration of its iodinated form to rats. Autoradiography at 5 and 30 min after the injection showed that 125I-trafermin is localized specifically in the fenestrated endothelium through binding to heparan sulfate proteoglycans (HSPG) in liver, kidney, adrenal, spleen, hypophysis and bone marrow. Metabolites in the organs were examined at 5 min and 24 h after the injection. More than 73% of radioactivity in liver and kidney was extractable at either time point, and a large majority of the extracted radioactivity was heparin-binding. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the substantial radioactivity recovered from liver and kidney can commonly be attributed to a peptide with the same molecular weight as the intact trafermin (B-1, 17.7 kDa) and only three truncated metabolites (B-2, 15.0 kDa; B-3, 7.2 kDa; B-4, 4.2 kDa). Because no truncated metabolites were found in serum, these metabolites seem to be produced inherently in liver and kidney. Although they all retained heparin-binding capacity, only B-1 and B-2 exhibited a stimulatory effect on proliferation of endothelial cells, and these bioactive peptides disappeared completely from liver within a day, indicating a rapid inactivation process in the organs. Taken together with the morphological evidence on autoradiography, it seems most likely that the injected trafermin could be inactivated in sinusoidal endothelial cells, probably through a well-known internalization mechanism of the basic fibroblast growth factor-HSPG complex.

Pheochromocytoma in a long-term hemodialysis patient, discovered as an adrenal incidentaloma

A case of pheochromocytoma was discovered incidentally during long-term hemodialysis for chronic renal failure due to acquired cystic kidney disease. A 52-year-old male patient was examined for weight loss of 3 kg during over a period of 3 months. Abdominal computed tomography (CT) revealed a left adrenal mass (3.0 cm in size). Plasma adrenaline and noradrenaline were increased to 521 pg/ml and 1,341 pg/ml, respectively, and the metoclopramide provocative test was positive. Further, in the scintiscan using 123I-metaiodobenzylguanidine (MIBG), an accumulation of the radionuclide in the left adrenal tumor region was confirmed. The patient is currently under observation and conservative treatment due to the possible occurrence of arterial hypotension after resection of the tumor and to lesser possibility of the malignancy.

Temporal and regional profiles of cytoskeletal protein accumulation in the rat brain following traumatic brain injury

To characterize the cytoskeletal aberration due to traumatic injury, temporal and regional profiles of changes in immunoreactivity of microtubule-associated protein 2 (MAP2), neurofilament heavy subunit protein (NFH) and heat shock protein 72 (HSP72) were investigated after different magnitudes of traumatic brain injury by fluid percussion. The experimental rat brain was perfusion-fixed at 1, 6 and 24 hours after traumatic brain injury. Conventional histological staining has demonstrated that the mildest traumatic brain injury (1.0 atm) induced no neuronal loss at the impact site and that neuron loss was apparent when traumatic brain injury was increased to 4.3 atm. The mildest traumatic brain injury, however, caused a significant increase in HSP72 immunoreactivity in the superficial cortical layers at the impact site as early as 1 hour after the injury. In the case of severe traumatic brain injury (4.3 atm), neuron loss was apparent in the area at the impact site, but the increase in HSP72 immunoreactivity was moderate, and it was observed only after 6 hours in the deep cortical layers under the necrotic area. The increased immunostaining of MAP2 was demonstrated in damaged axons and neuronal perikarya in the wider area surrounding the impact site at 6 and 24 hours after the injury. Six and 24 hours after the injury, perikaryal accumulation of neurofilament was observed, and the accumulated neurofilament was mostly phosphorylated. These results indicate that the severe traumatic brain injury of 4.3 atm triggers the abnormal accumulation of cytoskeletal proteins in neuronal perikarya, most probably due to an impairment of axonal transport. It is implied that the increased expression of HSP72 may be involved in the protective process of neurons after traumatic brain injury.

AtPLC2, a gene encoding phosphoinositide-specific phospholipase C, is constitutively expressed in vegetative and floral tissues in Arabidopsis thaliana

A cDNA encoding a phosphoinositide-specific phospholipase C (PI-PLC) from the higher plant Arabidopsis thaliana was cloned and characterized. The gene corresponding to this cDNA is designated AtPLC2. The overall structure of the predicted AtPLC2 protein is similar to those of plant PI-PLCs and mammalian delta-type PI-PLCs. Northern blot analysis revealed that AtPLC2 is expressed constitutively whereas AtPLC1S, another gene for PI-PLC of Arabidopsis, is induced by environmental stresses such as dehydration and salinity, indicating that the function of AtPLC2 is distinct from that of AtPLC1S. The AtPLC2 mRNA was detected in vegetative and floral tissues. We determined the positions of these two PI-PLCs genes on Arabidopsis chromosomes by RFLP mapping using P1 genomic clones.