[Research progress on the application of non-nutritional effects of fat emulsion in the treatment of poisoning]

Fat emulsion is a drug commonly used clinically for parenteral nutrition support in critically ill patients.With the development of the pharmaceutical industry, fat emulsion has formed a variety of different formulations, among which different types of fat emulsion have their own metabolic and body energy supply characteristics, and the application indications are also different. In addition to providing the supply of nutrients, the role of fat emulsion in anti-toxicity, immune regulation, anti-inflammatory, anti-shock, cardiopulmonary resuscitation and other aspects has gradually been discovered. This article reviews the existing evidence-based medical evidence and expounds the mechanism and therapeutic role of fat emulsion in the treatment of critically ill patients with poisoning. Its value in the treatment of critically ill patients with poisoning was discussed, and some references were provided for the application of non-nutritional functions of fat emulsion in the future.

[Clinical analysis of 25 cases of acute oral 84 disinfectant poisoning]

Objective: To summarize the clinical characteristics and treatment effect of patients with acute oral 84 disinfectant poisoning, so as to improve the understanding, diagnosis and treatment of the disease. Methods: In January 2022, 25 hospitalized patients with acute oral 84 disinfectant poisoning admitted to our department from March 2016 to August 2021 were selected as the research objects, and their general conditions, poisoning reasons, poisoning time, dose of poisoning, clinical manifestations, blood routine and biochemical indicators, diagnosis, treatment and prognosis were selected. Results: A retrospective analysis was performed. Among the 25 patients, there were 4 males and 21 females, aged from 20 to 91 years, and M (Q(1), Q(3)) was 38.7 (27, 46) years; The poisoning time (from exposure to poison to treatment) was 1~72 h, and M (Q(1), Q(3)) was 10.5 (3, 11.5) h. The length of stay was 1~20 days, and M (Q(1), Q(3)) was 5.72 (2, 7) days.The dose was 40-500 ml, and the M (Q(1), Q(3)) was 219.6 (100, 330) ml. Chest CT showed exudative changes in both lungs in 4 patients, excessive decreased permeability in 1 case and pleural effusion in 1 case. Gastroscope showed 2 cases of erosive inflammation of gastric body and antrum, 1 case of esophageal ulcer and cardiac ulcer, 1 case of corrosive gastritis, gastric fundus ulcer and esophageal stenosis. Abdominal X-ray showed 1 case of abdominal intestinal dilatation and pneumatosis with multiple gas-liquid planes.There were 1 case of type I respiratory failure, 6 cases of gastrointestinal bleeding and 1 case of incomplete intestinal obstruction. There were 19 cases of nausea and vomiting, 9 cases of abdominal pain, 6 cases of pharyngeal pain and 6 cases of retrosternal burning pain, 1 case of cough and 2 cases of fatigue. Conclusion: Acute oral 84 disinfectant will cause varying degrees of damage to the human digestive tract and lungs. In severe cases, gastrointestinal bleeding, intestinal obstruction, hypoxemia, etc, and even life-threatening, should be paid attention to clinically. The treatment is mainly symptomatic support treatment, such as protecting gastrointestinal mucosa, controlling acute inflammatory reaction, protecting the functions of liver and kidney and other important organs.

[Clinical analysis of 15 cases of acute glufosinate poisoning]

The glufosinate poisoning can cause damage to the respiratory system and nervous system. In severe cases, respiratory failure and toxic encephalopathy are life-threatening. It should be paid attention to and supportive treatment.In this paper, 15 cases of acute oral glyphosate poisoning diagnosed by toxicant test in the Poisoning Treatment Center of the Army from March to August 2018 were analyzed, and the clinical characteristics and treatment effect of acute glyphosate poisoning were summarized, so as to improve the understanding, diagnosis and treatment level of the disease.

Bioinformatic analysis of the nucleotide binding site-encoding disease-resistance genes in foxtail millet (Setaria italica (L.) Beauv.)

The nucleotide-binding site (NBS) disease-resistance genes are the largest category of plant disease-resistance gene analogs. The complete set of disease-resistant candidate genes, which encode the NBS sequence, was filtered in the genomes of two varieties of foxtail millet (Yugu1 and 'Zhang gu'). This study investigated a number of characteristics of the putative NBS genes, such as structural diversity and phylogenetic relationships. A total of 269 and 281 NBS-coding sequences were identified in Yugu1 and 'Zhang gu', respectively. When the two databases were compared, 72 genes were found to be identical and 164 genes showed more than 90% similarity. Physical positioning and gene family analysis of the NBS disease-resistance genes in the genome revealed that the number of genes on each chromosome was similar in both varieties. The eighth chromosome contained the largest number of genes and the ninth chromosome contained the lowest number of genes. Exactly 34 gene clusters containing the 161 genes were found in the Yugu1 genome, with each cluster containing 4.7 genes on average. In comparison, the 'Zhang gu' genome possessed 28 gene clusters, which had 151 genes, with an average of 5.4 genes in each cluster. The largest gene cluster, located on the eighth chromosome, contained 12 genes in the Yugu1 database, whereas it contained 16 genes in the 'Zhang gu' database. The classification results showed that the CC-NBS-LRR gene made up the largest part of each chromosome in the two databases. Two TIR-NBS genes were also found in the Yugu1 genome.

First Report of Fusarium equiseti Causing a Sheath Rot of Corn in China

Corn is the most important cereal crop in China. Over 34.94 million ha of corn is cultivated in the country annually. However, fungal diseases are a major limiting factor in corn production. In August 2008, 50 ha in several corn fields in Liaoning, Jilin, and Heilongjiang provinces were observed to be severely affected by a disease causing a yield loss of 30%. Results from field surveys suggested an epidemic during late corn growth stages that affected corn sheaths, causing irregularly circular spots with grayish brown to dark brown lesions. Lesions ranged from 2.5 to 3 × 3 to 5 cm. To isolate the causal agent, tissue was removed from the border of lesions and surface sterilized in 75% ethanol for 30 sec and 0.1% HgCl₂ for 1 min. The sample was then triple rinsed in sterile distilled water. The isolate was purified and subcultured on potato dextrose agar (PDA) at 25 ± 2°C. The initial color of the mycelium was white, turning brown after being cultured for 7 days. A pale brown to dark brown pigment developed in the agar beneath the colony. Chlamydospores, solitary but also in short chains, measuring 7.2 to 15.3 μm, were produced on carnation leaf agar (CLA) after 10 days and became verrucose 20 days later. Macroconidia were produced on CLA in orange sporodochia from monophialides on branched conidiophores, usually 5- to 7-septate, and apical cells were tapered and elongate. Basal cells were prominent, foot-shaped, and elongated in appearance. Microconidia were not observed (1). These morphological characteristics matched the description of Fusarium equiseti reported by Leslie and Summerell (1). A pathogenicity test was conducted with an isolate from each of the 36 corn plants by spraying 2 ml of spore suspension (10⁶ conidia/ml) on 45-day-old corn sheaths (cv. Huang Zao). For the control treatment, 36 corn plants were sprayed with an equal volume of sterilized water. Inoculated plants were placed in a greenhouse at 32 to 34°C and 95% relative humidity. Typical irregularly circular lesions were observed 7 days after inoculation, except in the control samples. Each treatment was replicated three times. The suspected pathogen was consistently re-isolated from diseased tissue according to Koch's postulates, and was found to be morphologically similar to F. equiseti. Preliminary morphological identification of the fungus was confirmed by a PCR assay using genomic DNA extracted from the mycelia of a 7-day-old culture on PDA at 25 ± 2°C. A 750-bp amplified region of the transcription elongation factor (TEF) of rDNA was generated using TEF1 (5'-ATGGGTAAGGAGGACAAGAC-3') and TEF2 (5'-GGAAGTACCAGTGATCATGTT-3') primers. The TEF region (GenBank Accession No. KF754798) was sequenced by Sangon Biotech Co., Ltd. (Shanghai, China) and displayed 99% nucleotide similarity with the rDNA-TEF of F. equiseti (JN127347.1) separately after a BLASTn search in GenBank. Based on the symptoms, fungal morphology, TEF sequence, and pathogenicity testing, this fungus was identified as F. equiseti. To our knowledge, this is the first report of F. equiseti on corn sheaths in China. This report will establish a foundation for further study of F. equiseti to address the disease effectively and to determine the severity of damage caused by F. equiseti. Reference: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell, Ames, IA, 2006.

First Report of Elm Yellows Subgroup 16SrV-B Phytoplasma as the Cause of Rose Balsam Phyllody in China

Rose balsam (Impatiens balsamina L.) is an ornamental species frequently cultivated in China and the red flower is often used as nail polish in rural regions. The phytoplasmas previously reported with rose balsam phyllody in China have been classified as aster yellows group (16SrI) (1). In August 2012, some rose balsams were observed with typical phytoplasma symptoms in Handan City, Hebei Province, China, with an incidence of about 70% in the fields. The flowers turned green and petals fascicled. The new leaves wrinkled and deformed and internodes shortened. Infected plants were stunted, matured prematurely, and failed to produce seeds. To confirm phytoplasma infection, 100 mg of plant tissue (leaves, petals) was collected from five symptomatic and four asymptomatic plants and total DNA was extracted using a modified cetyltrimethylammonium bromide (CTAB) method (2). The 16S rDNA gene was amplified by nested PCR using primer pair P1/P7 followed by R16F2n/R16R2 (3). No amplicons were generated with DNA from asymptomatic samples, but amplicons of approximately 1.2 kb were obtained with DNA from five symptomatic samples. The amplified products were purified with aTIANgel midi purification kit (Tiangen, Beijing) and sequenced at the Sangon Biotech facility (Shanghai, China). The sequences of the amplicons were 100% identical and deposited in NCBI GenBank (Accession No. KC993832). The 16S rDNA gene sequence from this phytoplasma was 99% similar to Jujube witches broom phytoplasma (JQ675716), Puna chicory flat stem phytoplasma (JN582266), Plum yellows phytoplasma (FJ459914), and other elm yellows group phytoplasmas by BLAST search of the NCBI database. Restriction fragment length polymorphism (RFLP) analyses were carried out by digesting the 1.2-kb R16F2n/R16R2 nested PCR product with restriction enzymes AluI, RsaI, HhaI, HpaI, Eco RI, TaqI, HaeIII, HinfI, and KpnI (Takara, Dalian). The 16S rDNA RFLP patterns matched that of Jujube witches broom phytoplasma (JWB, subgroup 16SrV-B) (4). Nucleotide sequences of rose balsam phyllody were analyzed by iPhyClassifier software, which revealed that it had maximum similarity to the reference pattern of 16Sr group V, subgroup B (AB052876). All samples were detected with transmission electron microscopy. The results showed phytoplasma-like cells in phloem sieve element of symptomatic plants, while no phytoplasma-like cells were observed in healthy phloem tissues. The phytoplasma cells ranged from 230 to 470 nm in diameter and were ellipsoidal or orbicular with visible membranes. Combining the RFLP pattern and sequence analysis by iPhyClassifier, we classified the phytoplasma causing rose balsam phyllody into subgroup 16SrV-B. To our knowledge, this is the first report of 16SrV-B group phytoplasmas infecting rose balsam in China. References: (1) Z. N. Li et al. J. Phytopathol. 159:799, 2011. (2) M. A. Saghai-Maroof et al. Proc. Natl. Acad. Sci. 81:8014, 1984. (3) I. M. Lee et al. Phytopathology 83:834, 1993. (4) I. M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998.

Purification and cloning of nicosulfuron-degrading enzymes from Bacillus subtilis YB1

The nicosulfuron-degrading enzymes from Bacillus subtilis strain YB1 were purified and their genes were cloned. The proteins of bacterial culture filtrate were precipitated with ammonium sulfate or acetone. The extracellular proteins concentrated by acetone were purified from DEAE-Sepharose Fast Flow chromatography. The four protein peaks eluted from DEAE-column were separated and purified by native PAGE. Three components (P1-1, P3-2, P4-3) had nicosulfuron-degrading activity, and component P4-3 degradated 57.5% of this compound. The molecular weights of the components were 33.5, 54.8 and 37.0 kDa, respectively. The amino acid sequences of nicosulfuron-degrading enzymes from B. subtilis YB1 were determined by MALDI-TOF-MS, indicating these enzymes as manganese ABC transporter, vegetative catalase 1 and acetoin dehydrogenase E1, respectively. Using PCR amplification, genes 918, 1428, 1026 bp in size were detected for the enzymes studied.

First Report of Bipolaris papendorfii Causing Corn Leaf Spot in China

Corn is the most important cereal crop in China, with over 34.94 million ha being cultivated in the country annually. However, fungal diseases are a major limiting factor in corn production. In August 2012, 20 ha of corn fields in Anhui Province were found to be heavily infected by fungi. The margin of the lesion was achlorotic, and the middle was yellowish white or off-white, which was similar to the corn Curvalaria leaf spot. The oval lesions were approximately 5 to 7 mm. Lesion tissue was removed from the border between symptomatic and healthy tissue. The surface was sterilized in 75% ethanol for 30 s and 0.1% HgCl₂ for 1 min, after which the sample was washed three times in sterile distilled water. The isolate was purified and subcultured on potato dextrose agar (PDA) at 25 ± 2°C. The initial color of the colony was light brown, turning dark brown after being cultured for 7 days. The conidia were boat-shaped or inverted pear-shaped and were clearly bent to one side. The cells of both ends were slightly lighter and respectively ranged from 34.5 to 44.0 μm and 12.0 to 21.0 μm away from the base, with the second cell as the widest. The majority conidia had three or four false septates; isolates produced light brown to medium brown conidiophore, scattered or clustered, often branching, and exhibited bending. These morphological characteristics matched with the description of Bipolaris papendorfii reported by Zhang (3). A pathogenicity test was conducted with the two isolates on each of the 36 corns by spraying 2 ml spore suspension (10⁶ conidia/ml). For the control treatment, 36 corns were inoculated with an equal volume of sterilized water. Inoculated plants were placed in a greenhouse from 29 to 33°C and 95% relative humidity. The typical 5 to 7 mm oval lesions were observed 7 days after inoculation, except on the control samples. Three replications of 36 corns were used for each treatment. The isolate was consistently 100% reisolated from the diseased tissue according to Koch's postulate. The isolate was found to be morphologically similar to B. papendorfii. Preliminary morphological identification of the fungus was confirmed by PCR assay using genomic DNA extracted from the mycelium of a 7-day-old culture on PDA at 25 ± 2°C. A 550-bp amplified region of the internal transcribed spacer (ITS) of rDNA was generated using ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3') universal primers (1). The ITS region (GenBank Accession No. KC592365) was then sequenced by Sangon Biotech (Shanghai, China), and displayed 99% nucleotide similarity with the rDNA-ITS of B. papendorfii (JQ753972.1) separately after BLASTn research in GenBank. Based on the symptoms, fungal morphology, ITS sequence, and pathogenicity testing, this fungus was identified as B. papendorfii. The pathogen could reportedly infect tobacco and cotton (2). To our knowledge, this is the first study to report that B. papendorfii can infect corn in China. This report will establish a foundation for the further study of B. papendorfii to address the disease effectively. Further studies will be conducted to determine the incidence of the disease and the severity of damage caused by B. papendorfii as well as determine a possible mode for controlling the spread of the disease. References: (1) Y. J. Cao et al. Chin. J. Trop. Crops 31:1098, 2010. (2) H. Deng et al. Mycosystema 21:327, 2002. (3) T. Y. Zhang. Chin. Fungi Chi. 30:21, 2010.

Degradation of nicosulfuron by Bacillus subtilis YB1 and Aspergillus niger YF1

The optimal degrading conditions for the nicosulfuron degradation by Bacillus subtilis YB1 and Aspergillus niger YF1, and site of their action on nicosulfuron were studied. The results showed that the degradation efficiency of free cells of B. subtilis YB1 and A. niger YF1 was respectively 87.9 and 98.8% in basic medium III containing 2 mg/l of nicosulfuron after inoculation with 1 ml of culture containing 2.3 x 10(7) CFU ml(-1) and incubation for 5 days at 35 degrees C. Moreover, the degradation rate of nicosulfuron by the mixture of microorganisms was much higher than for every of them taken separately in the same conditions. The mass spectrometric analysis of the products degraded by B. subtilis YB1 revealed that the sulfonylurea bridge in nicosulfuron molecule had been broken. Extracellular (EXF) and endocellular (ENF) fractions obtained from bacterium and fungus were tested for the ability to degrade nicosulfuron. The degradation efficiency of fractions extracted from B. subtilis YBI was 66.8% by EXF and 15.8% by ENF, but neither EXF nor ENF extracted from A. niger YFI had the activity of degrading nicosulfuron.

First Report of Elm Yellows Subgroup 16SrV-B Phytoplasma Infecting Chinese Tulip Tree in China

Chinese tulip tree (Liriodendron chinensis) is native to China and is planted all around the country as an ornamental tree. In July of 2011, some Chinese tulip trees with typical phytoplasma symptoms were found in Baoding City, Hebei Province, China. Symptoms included yellowing of leaves, slow decline, little leaves, and death of entire plants. To confirm phytoplasma infection of these plants, total DNA was extracted from 100 mg of fresh leaf midribs collected from leaves of nine symptomatic and eight asymptomatic plants with a plant DNA extract kit (Tiangen, Beijing, China) according to the manufacturer's protocols. Using 16S rRNA phytoplasma universal primer pairs P1/P7 followed by R16F2n/R16R2, a nest PCR was carried out (1,2). The results showed that the phytoplasma was only detected in symptomatic samples by nested PCR, while the asymptomatic were negative. An approximate 1.2-kb specific fragment was obtained from the DNA of nine symptomatic plants, but no product was amplified from the leaves of eight healthy ones. The amplified products were cloned and sequenced. The sequence was deposited in GenBank Data Libraries under Accession No. JQ585925 and shared the highest homology of 99% with Puna chicory flat stem phytoplasma (GenBank Accession No. JN582266), Apricot leaf roll phytoplasma (GenBank Accession No. FJ572660), Jujube witches'-broom phytoplasma (GenBank Accession No. AY197661), and other elm yellows group phytoplasmas by BLAST analysis with that of other phytoplasmas from GenBank. Meanwhile, the sequence data was analyzed by iPhyClassifier software and the result showed that the 16S rDNA F2nR2 fragment was identical (similarity coefficient 1.00) to the reference patterns of 16Sr group V, subgroup B (GenBank Accession No.AB052876) (3). Combining the BLAST analysis in GenBank and the analysis of iPhyClassifier, we classified the phytoplasma causing Chinese tulip tree yellow leaves disease into subgroup 16SrV-B. To our knowledge, this is the first report of the 16SrVB group phytoplasmas infecting Chinese tulip tree in China. References: (1) I. M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) I. M. Lee et al. Int. J. Syst. Evol. Microbiol. 54:337, 2004. (3) Y. Zhao et al. Int. J. Syst. Evol. Microbiol. 59:2582, 2009.

Natural occurrence of fumonisins b1 and b2 in corn from three main production provinces in China

A total of 255 corn samples collected in 2010 from three main corn production provinces of China (Liaoning, Shandong, and Henan) were analyzed for contamination with fumonisins (FB(1) and FB(2)). The incidence of contamination was significantly higher in samples from Liaoning than in samples from the other two provinces. Approximately 80.0% of the samples from Liaoning were contaminated with fumonisins, with a mean total fumonisin concentration of 3,990 ng/g. In contrast, the mean total fumonisin concentrations were 845 and 665 ng/g in samples from Shandong and Henan, respectively. The probable daily intake of fumonisins (0.3 μg/kg of body weight) is within the provisional maximum tolerable daily intake of 2.0 μg/kg of body weight set by the Joint Food and Agriculture Organization and World Health Organization Expert Committee on Food Additives.

Characterization and haplotype analysis of 10 novel Y-STR loci in Chinese Han population

In this study, we analyzed allelic sequences of 10 novel Y-specific STR loci, DYS454, DYS510, DYS513, DYS520, DYS542, DYS544, DYS552, DYS561, DYS587 and DYS593, surveyed the distribution of haplotypes in a Chinese Han population. Extracted DNA was amplified with PCR, followed by a horizontal non-denaturing polyacrylamide gel electrophoresis with discontinuous buffer system. Purified alleles were sequenced on DNA sequencer (ABI Model 377) to verify the number of motif repeats. The number of alleles observed at each locus ranged from 3 to 8, yielding 102 haplotypes in 103 unrelated males samples. The allele diversity values for each locus ranged from 0.2099 (DYS544) to 0.7523 (DYS552). The haplotype diversity using all these loci was 0.9998. Our study revealed that they were valuable Y-specific markers for forensic applications.

Further characterization and population data for the pentanucleotide STR polymorphism D10S2325

Pentanucleotide tandem repeat markers are interesting for forensic sciences, because they may present less stutter on the electrophoretic pattern. We focused on the analysis of the DNA sequence for each allele at the pentanucleotide STR locus D10S2325 in order to understand their structures in the human genome and to construct human allelic ladder, which is necessary for forensic DNA typing. In order to evaluate the forensic applicability of D10S2325 and to construct a preliminary database, the genotype distributions and allele frequencies in three major ethnic groups were investigated. The population samples included Caucasians (Germans), Africans (African Americans), and Asians (Chinese). A total of 520 samples from unrelated individuals was analyzed by Amp-FLP. An example of each allele and new alleles were sequenced. Allele determination was carried out by comparison with a sequenced human allelic ladder made in-house. This pentanucleotide STR provided easily interpretable results. A total of 15 alleles was found in our population samples. Three new alleles were observed and named as alleles 19 and 21 based on the number of repeat motifs, while allele 19 can be divided further into two alleles, 19a and 19 according to analysis of the sequence. No evidence of deviation from Hardy-Weinberg equilibrium was observed. In 64 confirmed father/mother/child triplets no mutation event was observed. Using a maximum likelihood method, the mutation rate was indirectly estimated as 2.5 x 10(-5). These results suggest that D10S2325 is a useful marker for forensic casework and paternity analysis.

Theoretical and experimental CD of conformationally flexible complex molecules-application to ouabain pentanaphthoate and analogs

Theoretical calculation of circular dichroic exciton-coupled spectra of ouabain 1,19,2',3',4'-pentanaphthoate and its analogs was executed by a combination of conformational analysis with molecular mechanics and quantum-chemical calculation. Most of the calculated CD spectra show good agreement with the corresponding experimental data, which suggests that the method may be generalized for applications to other conformationally flexible natural products. The CD calculation was then used to evaluate the plausibility of "fortuitous CD cancellation," which was observed in the microscale naphthoylation study of hypothalamic inhibitory factor, a presumed ouabain isomer from bovine hypothalamus.

Theoretical calculation of circular dichroic exciton-split spectra in presence of three interacting 2-naphthoate chromophores

Ample experimental evidence shows that the principle of pairwise additivity holds in exciton coupled CD systems consisting of three or more interacting chromophores. This principle is one of the most important from a practical viewpoint. However, the rule has so far not been proven theoretically. In order to prove the additivity principle by calculation, three ouabagenin bisnaphthoates and 1,3,19-tris-naphthoates were chosen as models. Since this represents a challenging case where the 2-naphthoate chromophore can adopt s-cis or s-trans conformations and, moreover the C-19 side chain of ouabagenin is flexible, Monte Carlo conformational search was performed prior to the CD calculation. The pi-electron SCF-CI-DV MO calculation of CD was applied to all conformers within 3 kcal/mol range from the lowest energy. Good agreement between experimental and theoretical CD spectra was obtained for the ouabagenin bisnaphthoates and trisnaphthoate.

Structural studies of vinblastine alkaloids by exciton coupled circular dichroism

SCF-CI-dipole velocity MO calculations have shown that the bisignate circular dichroic curves of vinblastine/vincristine alkaloids at ca 210 and 220-230 nm are due to exciton coupling between the indoline and indole moieties. Furthermore, a combination of X-ray crystal structure data with MM2 local energy minimization provides a convenient means for estimation of the preferred solution conformation.

Activation of 1-aminocyclopropane-1-carboxylate oxidase by carbon dioxide

1-Aminocyclopropane-1-carboxylate (ACC) oxidase requires CO2/HCO3- as an essential activator for its activity. Taking advantage that the equilibrium concentrations of CO2 and HCO3- vary with pH and that the interconversions of CO2 and HCO3- are slower at low temperature, we identified CO2 rather than HCO3- as the active species involved in the activation process. Preincubation of the enzyme with a saturating concentration of CO2 resulted in increased activation of the enzyme when preincubation pH was raised, indicating that CO2 reacted with an enzyme group having an alkaline pKa. It is suggested that the CO2 activation of ACC oxidase involves the formation of a carbamate. CO2 increases the Vmax of the reaction but decreases the affinity of the enzyme toward its substrate ACC. A plausible reaction scheme accounting for the CO2 activation process is presented.

Purification and characterization of 1-aminocyclopropane-1-carboxylate oxidase from apple fruit

1-Aminocyclopropane-1-carboxylate (ACC) oxidase catalyzes the oxidation of ACC to ethylene. Following conventional column fractionation, the enzyme was purified 180-fold to near homogeneity with a specific activity of 20 nmol/(mg.min). This purified enzyme preparation migrated as a single protein band with an apparent molecular mass of 35 kDa on SDS/PAGE and 39 kDa on gel filtration. As in vivo, the purified enzyme required CO2 for activity. Removal of CO2 from the reaction mixture completely abolished the enzyme activity, while 0.5% atmospheric CO2 (0.15 mM in the medium) gave half-maximal activity. The purified enzyme displayed an absolute requirement for Fe2+ and ascorbate. The stoichiometry of the enzymatic reaction was determined: ACC + ascorbate + O2-->C2H4 + HCN + CO2 + dehydroascorbate + 2 H2O. A polyclonal antibody was raised against a synthetic tridecapeptide (PDLEEEYRKTMKE) whose sequence was deduced from the apple pAE12 cDNA [Dong, J. G., Olson, D., Silverstone, A. & Yang, S. F. (1992) Plant Physiol. 98, 1530-1531], which is homologous to tomato cDNAs encoding ACC oxidase. On a Western blot, this antibody specifically recognized the purified ACC oxidase protein. The amino acid composition of the purified enzyme agreed well with that deduced from the pAE12 sequence. When the protein was cleaved with CNBr and one of the peptide fragments was isolated and sequenced for 20 cycles, its sequence (KEFAVELEKLAEKLLDLLCE) precisely matched that predicted from pAE12 (residues 115-134). When preclimacteric apple fruit was treated with ethylene, a parallel increase in in vivo and in vitro ACC oxidase activities was observed, and this increase was accompanied by a concomitant increase in the level of pAE12 transcript. These observations support the conclusion that the isolated ACC oxidase protein is encoded by pAE12.

Purification and characterization of 1-aminocyclopropane-1-carboxylate oxidase from apple fruit

1-Aminocyclopropane-1-carboxylate (ACC) oxidase catalyzes the oxidation of ACC to ethylene. Following conventional column fractionation, the enzyme was purified 180-fold to near homogeneity with a specific activity of 20 nmol/(mg.min). This purified enzyme preparation migrated as a single protein band with an apparent molecular mass of 35 kDa on SDS/PAGE and 39 kDa on gel filtration. As in vivo, the purified enzyme required CO2 for activity. Removal of CO2 from the reaction mixture completely abolished the enzyme activity, while 0.5% atmospheric CO2 (0.15 mM in the medium) gave half-maximal activity. The purified enzyme displayed an absolute requirement for Fe2+ and ascorbate. The stoichiometry of the enzymatic reaction was determined: ACC + ascorbate + O2-->C2H4 + HCN + CO2 + dehydroascorbate + 2 H2O. A polyclonal antibody was raised against a synthetic tridecapeptide (PDLEEEYRKTMKE) whose sequence was deduced from the apple pAE12 cDNA [Dong, J. G., Olson, D., Silverstone, A. & Yang, S. F. (1992) Plant Physiol. 98, 1530-1531], which is homologous to tomato cDNAs encoding ACC oxidase. On a Western blot, this antibody specifically recognized the purified ACC oxidase protein. The amino acid composition of the purified enzyme agreed well with that deduced from the pAE12 sequence. When the protein was cleaved with CNBr and one of the peptide fragments was isolated and sequenced for 20 cycles, its sequence (KEFAVELEKLAEKLLDLLCE) precisely matched that predicted from pAE12 (residues 115-134). When preclimacteric apple fruit was treated with ethylene, a parallel increase in in vivo and in vitro ACC oxidase activities was observed, and this increase was accompanied by a concomitant increase in the level of pAE12 transcript. These observations support the conclusion that the isolated ACC oxidase protein is encoded by pAE12.

Induction of 1-aminocyclopropane-1-carboxylate synthase mRNA by auxin in mung bean hypocotyls and cultured apple shoots

Auxin is known to promote ethylene production in vegetative tissues by increasing the activity of 1-aminocyclopropane-1-carboxylate (ACC) synthase; therefore, we have studied the effect of auxins on ACC synthase mRNA expression. Total RNA was isolated from auxin-incubated cultured apple (Malus sylvestris Mill.) shoots or mung bean (Vigna radiata L.) hypocotyls. These RNAs and a set of oligonucleotide primers corresponding to two conserved amino acid sequences (SNPLGTT and MSSFGLV) found in ACC synthases isolated from other species were used for polymerase chain reaction-based amplification of DNA fragments encoding the ACC synthase-active site domain. We obtained and sequenced a 290-base pair cDNA fragment (pAA1) from cultured apple shoots and a 328-base pair cDNA clone (pMBA1) from mung bean hypocotyls. Comparisons of their deduced amino acid sequences with those of previously characterized ACC synthase cDNAs indicate that both fragments are, indeed, closely related to ACC synthase cDNA. Northern blot analyses further showed that the expression of these transcripts is regulated by auxin treatment. These data indicate that auxin induces ethylene production transcriptionally by increasing the ACC synthase transcripts. The pAA1 shares 46% amino acid sequence homology with ripening-regulated apple fruit ACC synthase, indicating that ripening-regulated and auxin-regulated ACC synthases are encoded by different genes. In mung bean hypocotyls, aminooxyacetic acid, a potent inhibitor of ACC synthase activity, promoted the expression of auxin-induced ACC synthase mRNA, but cycloheximide inhibited this induction.

Cloning of a cDNA encoding 1-aminocyclopropane-1-carboxylate synthase and expression of its mRNA in ripening apple fruit

1-Aminocyclopropane-1-carboxylate (ACC) synthase (EC 4.4.1.14) purified from apple (Malus sylvestris Mill.) fruit was subjected to trypsin digestion. Following separation by reversed-phase high-pressure liquid chromatography, ten tryptic peptides were sequenced. Based on the sequences of three tryptic peptides, three sets of mixed oligonucleotide probes were synthesized and used to screen a plasmid cDNA library prepared from poly(A)(+) RNA of ripe apple fruit. A 1.5-kb (kilobase) cDNA clone which hybridized to all three probes were isolated. The clone contained an open reading frame of 1214 base pairs (bp) encoding a sequence of 404 amino acids. While the polyadenine tail at the 3'-end was intact, it lacked a portion of sequence at the 5'-end. Using the RNA-based polymerase chain reaction, an additional sequence of 148 bp was obtained at the 5'-end. Thus, 1362 bp were sequenced and they encode 454 amino acids. The deduced amino-acid sequence contained peptide sequences corresponding to all ten tryptic fragments, confirming the identity of the cDNA clone. Comparison of the deduced amino-acid sequence between ACC synthase from apple fruit and those from tomato (Lycopersicon esculentum Mill.) and winter squash (Cucurbita maxima Duch.) fruits demonstrated the presence of seven highly conserved regions, including the previously identified region for the active site. The size of the translation product of ACC-synthase mRNA was similar to that of the mature protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), indicating that apple ACC-synthase undergoes only minor, if any, post-translational proteolytic processing. Analysis of ACC-synthase mRNA by in-vitro translation-immunoprecipitation, and by Northern blotting indicates that the ACC-synthase mRNA was undetectable in unripe fruit, but was accumulated massively during the ripening proccess. These data demonstrate that the expression of the ACC-synthase gene is developmentally regulated.

Purification and characterization of 1-aminocyclopropane-1-carboxylate synthase from apple fruits

1-Aminocyclopropane-1-carboxylate (ACC) synthase, a key enzyme in ethylene biosynthesis, was isolated and partially purified from apple (Malus sylvestris Mill.) fruits. Unlike ACC synthase isolated from other sources, apple ACC synthase is associated with the pellet fraction and can be solubilized in active form with Triton X-100. Following five purification steps, the solubilized enzyme was purified over 5000-fold to a specific activity of 100 micromoles per milligram protein per hour, and its purity was estimated to be 20 to 30%. Using this preparation, specific monoclonal antibodies were raised. Monoclonal antibodies against ACC synthase immunoglobulin were coupled to protein-A agarose to make an immunoaffinity column, which effectively purified the enzyme from a relatively crude enzyme preparation (100 units per milligram protein). As with the tomato enzyme, apple ACC synthase was inactivated and radiolabeled by its substrate S-adenosyl-l-methionine. Apple ACC synthase was identified to be a 48-kilodalton protein based on the observation that it was specifically bound to immunoaffinity column and it was specifically radiolabeled by its substrate S-adenosyl-l-methionine.

Characterization and sequencing of the active site of 1-aminocyclopropane-1-carboxylate synthase

The pyridoxal phosphate (PLP)-dependent 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4.1.14), the key enzyme in ethylene biosynthesis, is inactivated by its substrate S-adenosylmethionine (AdoMet). Apple ACC synthase was purified with an immunoaffinity gel, and its active site was probed with NaB3H4 or Ado[14C]Met. HPLC separation of the trypsin digest yielded a single radioactive peptide. Peptide sequencing of both 3H- and 14C-labeled peptides revealed a common dodecapeptide of Ser-Leu-Ser-Xaa-Asp-Leu-Gly-Leu-Pro-Gly-Phe-Arg, where Xaa was the modified, radioactive residue in each case. Acid hydrolysis of the 3H-labeled enzyme released radioactive N-pyridoxyllysine, indicating that the active-site peptide contained lysine at position 4. Mass spectrometry of the 14C-labeled peptide indicated a protonated molecular ion at m/z 1390.6, from which the mass of Xaa was calculated to be 229, a number that is equivalent to the mass of a lysine residue alkylated by the 2-aminobutyrate portion of AdoMet, as we previously proposed. These results indicate that the same active-site lysine binds the PLP and convalently links to the 2-aminobutyrate portion of AdoMet during inactivation. The active site of tomato ACC synthase was probed in the same manner with Ado[14C]Met. Sequencing of the tomato active-site peptide revealed two highly conserved dodecapeptides; the minor peptide possessed a sequence identical to that of the apple enzyme, whereas the major peptide differed from the minor peptide in that methionine replaced leucine at position 6.

Variation in endoplasmic-reticulum-associated glycoproteins of carrot cells cultured in vitro

Glycoproteins extracted from microsomes of in-vitro-cultured cells of Daucus carota L. cv. US-Harumakigosun were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and detected by peroxidase-conjugated concanavalin A. The appearance of a glycoprotein with Mr 31 000 (GP 31) was correlated with the ability of cells to form somatic embryos. GP 31 appeared in embryogenic cells cultured in 2,4-dichlorophenoxyacetic acid (2,4-D)-containing medium, but not in somatic embryos and non-embryogenic cells; it disappeared when the cultures were transferred to auxin-free medium. Another glycoprotein with Mr 32 000 (GP 32) was detected only in non-embryogenic cells, regardless of the presence or absence of 2,4-D. Both glycoproteins, GP 31 and GP 32, were associated with the rough endoplasmic reticulum and were extractable with 0.05% deoxycholate.