RESUMO
The bovine TRIM28 gene was amplified from ovary tissue by using RT-PCR. The TRIM28 gene was inserted into the eukaryotic expression vector pIRES2-EGFP and transfected into bovine fetal fibroblasts by using Lipofectamine 3000. TRIM28 mRNA and protein were detected by fluorescence microscope and western blotting. The results showed that the full length of TRIM28 was cloned and pIRES2-EGFP-TRIM28 was constructed successfully. EGFP expression was observed, and the pIRES2-EGFP-TRIM28 transfected group expressed more TRIM28 protein than that by the pIRES2-EGFP group. The TIMR28 gene has been successfully transferred into bovine fetal fibroblasts.
Assuntos
Proteínas Repressoras/genética , Animais , Bovinos , Células Cultivadas , Clonagem Molecular , Feminino , Fibroblastos/metabolismo , Vetores Genéticos/genética , Ovário/metabolismo , Proteínas Repressoras/metabolismoRESUMO
Leprosy is a chronic infectious and neurological disease that is caused by infection of Mycobacterium leprae (M. leprae). A recent genome-wide association study indicated a suggestive association of LRRK2 genetic variant rs1873613 with leprosy in Chinese population. To validate this association and further identify potential causal variants of LRRK2 with leprosy, we genotyped 13 LRRK2 variants in 548 leprosy patients and 1078 healthy individuals from Yunnan Province and (re-)analyzed 3225 Han Chinese across China. Variants rs1427267, rs3761863, rs1873613, rs732374 and rs7298930 were significantly associated with leprosy per se and/or paucibacillary leprosy (PB). Haplotype A-G-A-C-A was significantly associated with leprosy per se (P=0.018) and PB (P=0.020). Overexpression of the protective allele (Thr2397) of rs3761863 in HEK293 cells led to a significantly increased nuclear factor of activated T-cells' activity compared with allele Met2397 after lipopolysaccharides stimulation. Allele Thr2397 could attenuate 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine-induced autophagic activity in U251 cells. These data suggest that the protective effect of LRRK2 variant p.M2397T on leprosy might be mediated by increasing immune response and decreasing neurotoxicity after M. leprae loading. Our findings confirm that LRRK2 is a susceptible gene to leprosy in Han Chinese population.
Assuntos
Povo Asiático/genética , Hanseníase/genética , Proteínas Serina-Treonina Quinases/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Criança , Pré-Escolar , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Haplótipos , Humanos , Hanseníase/etnologia , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Adulto JovemRESUMO
Objective: To analyze the epidemiological and clinical characteristics of imported COVID-19 cases after SARS-CoV-2 vaccination and to provide evidence for the prevention and control of COVID-19. Methods: The imported COVID-19 cases in Chengdu as of April 15, 2021 were divided into the vaccinated group and unvaccinated group according to the history of SARS-CoV-2 vaccination. The epidemiological and clinical data of the cases were collected retrospectively, and the differences in epidemiological and clinical characteristics of the two groups were compared. Laboratory tests consisted of nucleic acid test, clinical index test, serum antibody test and lymphocyte test. Software WPS2019 was used for data management and software R 4.0.3 was used for statistical analysis. Results: A total of 75 COVID-19 cases were included in the analysis, in which 20 had received SARS-CoV-2 vaccination and only 4 with clinical symptoms, 55 patients did not receive SARS-CoV-2 vaccination, and 16 had clinical symptoms. In vaccinated group, the first injection time of vaccination ranged from July to November 2020, and 10 cases received two doses of vaccine simultaneously and 10 cases received two doses of vaccine at intervals of 14-57 days. The intervals between the completion of vaccination and the onset ranged from 87 days to 224 days. The differences in classification and clinical type between the two groups were significant. Significant differences were observed in case classification and clinical type between vaccinated group and unvaccinated group (P<0.05). The vaccinated group had a relatively high proportion of asymptomatic infections (40.00%, 8/20), while mild infections were mainly observed in the unvaccinated group(76.36%,42/55). The differences in Ct values (ORF1ab gene and N gene) at the diagnosis were not significant between vaccinated group and unvaccinated group (P>0.05), similar results were also observed in lymphocyte subtypes, procalcitonin and C-reactive protein level comparisons. Serum amyloid A level was higher in unvaccinated group than in vaccinated group (P<0.05). However, the SARS-CoV-2 related serum antibody of IgM, IgG and total antibody levels were significantly higher in vaccinated group (P<0.05). Conclusions: Risk of infection still exists with SARS-CoV-2 after vaccination, which can facilitate the production of specific serum antibody of IgM and IgG when people are exposed to the virus. It has a certain protective effect on SARS-CoV-2 infected persons. Vaccination can reduce the clinical symptoms and mitigate disease severity.
Assuntos
Vacinas contra COVID-19/administração & dosagem , COVID-19 , Anticorpos Antivirais/sangue , COVID-19/epidemiologia , China/epidemiologia , Humanos , Estudos Retrospectivos , VacinaçãoRESUMO
MicroRNA166 (miR166) contributes to post-transcriptional regulation by binding the mRNAs of HD-ZIP III genes, which affects plant growth and development. The structural characteristics, expression, and functions of miR166 genes during the early somatic embryogenesis stage in Dimocarpus longan remain unknown. We isolated the transcripts of pri-miR166 S78 with two transcription initiation sites (TSSs) and pri-miR166 S338 with one TSS. These sequences contain potential smORFs and encode different miRNA peptides (miPEPs). Additionally, their promoters contain cis-acting elements responsive to diverse stimuli. The pre-miR166 S78 and pre-miR166 S338 expression levels were up-regulated in response to 2,4-D, abscisic acid, and ethylene. Although the expression patterns induced by hormones were similar, there were differences in the extent of the response, with pre-miR166 S338 more responsive than pre-miR166 S78. Thus, miRNA transcription and maturation are not simply linearly correlated. Moreover, pre-miR166 S78 and pre-miR166 S338 expression levels were down-regulated, whereas ATHB15 (target gene) expression was up-regulated, from the longan embryonic callus to the globular embryo stages. These results are indicative of a negative regulatory relationship between miR166 and ATHB15 during the early somatic embryogenesis stage in longan. At the same stages, miR166a.2-agomir, miR166a.2-antagomir, and miPEP166 S338 increased or decreased the expression of miR166a.2 and ATHB15, but with no consistent patterns or linear synchronization, from which we've found some reasons for it.
Assuntos
Regulação da Expressão Gênica de Plantas , MicroRNAs , Sapindaceae , MicroRNAs/genética , MicroRNAs/metabolismo , RNA Mensageiro/química , RNA Mensageiro/genética , Sapindaceae/genética , Sapindaceae/metabolismo , Sementes/genéticaRESUMO
BACKGROUND AND PURPOSE: Perivascular adipose tissue (PVAT) attenuates vascular contraction, but the mechanisms remain largely unknown. The possible involvement of endothelium (E) and hydrogen peroxide (H2O2) was investigated. EXPERIMENTAL APPROACH: Aortic rings from Wistar rats were prepared with both PVAT and E intact (PVAT+ E+), with either PVAT or E removed (PVAT- E+, or PVAT+ E-), or with both removed (PVAT- E-) for functional studies. Nitric oxide (NO) production was measured. KEY RESULTS: Contraction to phenylephrine and 5-HT respectively was highest in PVAT- E-, lowest in PVAT+ E+, and intermediate in PVAT+ E- or PVAT- E+. In bioassay experiments, transferring bathing solution incubated with a PVAT+ ring (donor) to a PVAT- ring (recipient) induced relaxation in the recipient. This relaxation was abolished by E removal, NO synthase inhibition, scavenging of NO, high extracellular K+, or blockade of calcium-dependent K+ channels (K(Ca)). The solution stimulated NO production in isolated endothelial cells and in PVAT- E+ rings. In E- rings, the contraction to phenylephrine of PVAT+ rings but not PVAT- rings was enhanced by catalase or soluble guanylyl cyclase (sGC) inhibitor, but reduced by superoxide dismutase and tiron. In PVAT- E- rings, H2O2 attenuated phenylephrine-induced contraction. This effect was counteracted by sGC inhibition. NO donor and H2O2 exhibited additive inhibition of the contraction to phenylephrine in PVAT- E- rings. CONCLUSION: PVAT exerts its anti-contractile effects through two distinct mechanisms: (1) by releasing a transferable relaxing factor which induces endothelium-dependent relaxation through NO release and subsequent K(Ca) channel activation, and (2) by an endothelium-independent mechanism involving H2O2 and subsequent activation of sGC.
Assuntos
Tecido Adiposo/fisiologia , Aorta Torácica/fisiologia , Vasoconstrição/fisiologia , Tecido Adiposo/metabolismo , Agonistas alfa-Adrenérgicos/farmacologia , Animais , Aorta Torácica/efeitos dos fármacos , Aorta Torácica/metabolismo , Relação Dose-Resposta a Droga , Endotélio Vascular/fisiologia , Inibidores Enzimáticos/farmacologia , Guanilato Ciclase/antagonistas & inibidores , Guanilato Ciclase/metabolismo , Peróxido de Hidrogênio/farmacologia , Técnicas In Vitro , Masculino , Músculo Liso Vascular/irrigação sanguínea , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/fisiologia , Doadores de Óxido Nítrico/farmacologia , Óxido Nítrico Sintase/antagonistas & inibidores , Nitroarginina/farmacologia , Fenilefrina/farmacologia , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio/fisiologia , Ratos , Ratos Wistar , Serotonina/farmacologia , Tetraetilamônio/farmacologia , Vasoconstrição/efeitos dos fármacos , Vasodilatação/efeitos dos fármacosRESUMO
Taiwan has experienced several outbreaks of enterovirus 71 (EV71) infections since 1998. This study examined the quantitative relationship between specific cytokines in the cerebrospinal fluid (CSF) and the severity of EV71 brain stem encephalitis (BE), and investigated whether the CSF cytokine response differed from that to uncomplicated echovirus meningitis (EM). The study included 57 children with EV71 BE, of whom 24 had isolated BE, 24 had autonomic nervous system (ANS) dysregulation, and nine had pulmonary oedema (PE), and 15 children with EM. All were confirmed by virus culture. Mean CSF glucose, total protein and lactate levels were increased significantly in association with the severity of EV71 BE. The mean CSF concentration of interleukin (IL)-1beta in children with EV71 PE was significantly higher than in those with isolated BE. IL-6 and interferon (IFN)-gamma levels were significantly higher for EV71 PE and ANS dysregulation than for isolated BE. In contrast, EM was associated with high levels of IL-1beta and low levels of IFN-gamma. Cytokines in the central nervous system, as well as in blood, appear to be involved in the pathogenesis of EV71 BE.
Assuntos
Tronco Encefálico/fisiopatologia , Citocinas/líquido cefalorraquidiano , Encefalite Viral/fisiopatologia , Infecções por Enterovirus/imunologia , Enterovirus/patogenicidade , Tronco Encefálico/imunologia , Tronco Encefálico/virologia , Pré-Escolar , Surtos de Doenças , Infecções por Echovirus/epidemiologia , Infecções por Echovirus/imunologia , Infecções por Echovirus/fisiopatologia , Infecções por Echovirus/virologia , Encefalite Viral/epidemiologia , Encefalite Viral/imunologia , Encefalite Viral/virologia , Enterovirus/imunologia , Enterovirus Humano B/imunologia , Enterovirus Humano B/patogenicidade , Infecções por Enterovirus/epidemiologia , Infecções por Enterovirus/fisiopatologia , Infecções por Enterovirus/virologia , Feminino , Humanos , Lactente , Masculino , Meningite Viral/epidemiologia , Meningite Viral/imunologia , Meningite Viral/fisiopatologia , Meningite Viral/virologia , Índice de Gravidade de Doença , Taiwan/epidemiologiaRESUMO
Auxin is known to be involved in all the stages of fruit development. Aux/IAAs are regulators of the auxin signaling at the transcription level. In a recent study, using RNAi strategy to limit the expression Sl-IAA17, it was shown that this tomato AuxIAA regulates fruit size mainly through altering the ploidy level of pericarp cells. Indeed, Sl-IAA17 down-regulated lines showed fruit with larger diameter, bigger volume and heavier weight than wild-type. The increase in fruit size was associated with thicker pericarp rather than larger locular spaces. The thicker pericarp was linked to larger cells harboring higher ploidy level, probably due to more active endoreduplication at the beginning of fruit development. The present report describes some additional phenotypes, not described in the initial article, among which are soluble solid content, juice pH, firmness, seed weight and fruit morphology.
Assuntos
Frutas/crescimento & desenvolvimento , Frutas/metabolismo , Ácidos Indolacéticos/metabolismo , Proteínas de Plantas/metabolismo , Solanum lycopersicum/crescimento & desenvolvimento , Solanum lycopersicum/metabolismo , Etilenos/biossíntese , Concentração de Íons de Hidrogênio , Interferência de RNARESUMO
The authors studied depressive symptoms among 251 Chinese medical inpatients through the use of the Beck Depression Inventory. Assessment of 100 healthy Chinese volunteers validated the use of American score norms for Chinese subjects. A total of 47.8% of the 251 medical inpatients (N = 120) met the Beck scale criterion for depression. Beck scale scores varied with the occupation of patients and the severity of medical illness but did not vary with sex, age, marital status, duration of hospitalization, or medical diagnosis.
Assuntos
Depressão/diagnóstico , Doença/psicologia , Etnicidade , Hospitalização , Adolescente , Adulto , Fatores Etários , Idoso , Criança , China/etnologia , Depressão/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ocupações , Inventário de PersonalidadeRESUMO
Parental and teacher ratings of adjustment on the Achenbach Child Behavior Checklist and Teacher Rating Form were obtained on 39 subjects diagnosed as having attention deficit disorder with hyperactivity (ADDH), 31 subjects with ADDH plus learning disability (ADDH-LD), and 29 controls. Subjects were all males between the ages of 9 and 11 years and resided in Changsha, People's Republic of China. Significant group differences were found between the two clinical groups and the control group. Ratings by parents and teachers of the ADDH and ADDH-LD groups indicated more behavior problems and poorer social adjustment than controls. ADDH and ADDH-LD groups were not significantly different from one another except on ratings of school and learning problems.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/diagnóstico , Comparação Transcultural , Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Criança , China , Humanos , Masculino , Testes PsicológicosRESUMO
Intracerebroventricular injection of senktide, a selective agonist for neurokinin B receptor (NK3), induced Fos expression in many neurons of the rat hypothalamus. Fos-positive neurons were predominantly present in the supraoptic and paraventricular hypothalamic nuclei, and some of them were seen in the lateral preoptic area, lateral hypothalamic area, arcuate nucleus, perifornical region, posterior hypothalamic area, circular nucleus, and along relatively large blood vessels (lateral hypothalamic perivascular nucleus) in the anterior hypothalamus. A double labeling study was performed to examine if vasopressin-containing neurons in the hypothalamus could be activated by the treatment. Neurons with both Fos-like immunoreactivity (-LI) and vasopressin-LI were found in the paraventricular nucleus, supraoptic nucleus, circular nucleus and lateral hypothalamic perivascular nucleus. In the supraoptic nucleus, about 87% of vasopressin-containing neurons exhibited Fos-LI, which corresponded to about 64% of Fos-positive neurons in the nucleus. In the paraventricular nucleus, about 80% of vasopressin-like immunoreactive neurons exhibited Fos-LI, which constituted about 51% of the total population of Fos-positive neurons in the region. The results suggest that NK3 receptor may be involved in the modulation of release of vasopressin from the hypothalamus in the rat.
Assuntos
Hipotálamo/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Proteínas Proto-Oncogênicas c-fos/efeitos dos fármacos , Substância P/análogos & derivados , Vasopressinas/metabolismo , Animais , Hipotálamo/metabolismo , Masculino , Neurônios/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Substância P/farmacologiaAssuntos
Mastócitos/enzimologia , Neoplasias de Tecido Conjuntivo/enzimologia , Nucleotidiltransferases , Trifosfato de Adenosina , Animais , Cromatografia , Cromatografia em Papel , Difosfatos , Estabilidade de Medicamentos , Ácido Edético , Eletroforese , Ativação Enzimática , Concentração de Íons de Hidrogênio , Hidroxiapatitas , Cinética , Magnésio , Manganês , Camundongos , Nucleotídeos , Nucleotidiltransferases/antagonistas & inibidores , Nucleotidiltransferases/isolamento & purificação , Isótopos de Fósforo , Sulfatos , Isótopos de Enxofre , ZincoRESUMO
A malonyltransferase isolated from mungbean (Vigna radiata L.) hypocotyls catalyzed the malonylation of both 1-aminocyclopropane-1-carboxylic acid (ACC) and D-amino acids. The possibility that ACC was recognized by the enzyme as a D-amino acid was investigated by examining the efficiencies of the four stereoisomers of 1-amino-2-ethylcyclopropane-1-carboxylic acid (AEC) serving as substrates of malonyltransferase and as inhibitors of ACC malonyltransferase. Although all four isomers were malonylated by the enzyme and competitively inhibited the malonylation of ACC to N-malonyl-ACC, (1R,2S)-AEC and (1R,2R)-AEC, both of which have an R-configuration as a D-amino acid, had lower Km and Ki values (0.1 to 0.2 mM) than their enantiomers, (1S,2R)-AEC (Km and Ki values were about 1 mM) and (1S,2S)-AEC (Km and Ki values were higher than 10 mM), which have an S-configuration as an L-amino acid. Similarly, (R)-isovaline (2-amino-2-methylbutanoic acid), which has an R-configuration as a D-amino acid, inhibited more effectively the enzymatic conversion of ACC to malonyl-ACC than did (S)-isovaline, which has an S-configuration as an L-amino acid. In mungbean hypocotyls (1R,2S)-AEC and (1R,2R)-AEC were also more efficiently converted into malonyl conjugates and more efficiently inhibited the conversion of radioactive ACC into malonyl-ACC than their enantiomers, although the differences in efficiency among stereoisomers were smaller in hypocotyls than in enzymatic reactions. These results suggest that ACC is recognized by the enzyme as a D-amino acid.
Assuntos
Aciltransferases/metabolismo , Aminoácidos Cíclicos , Aminoácidos/metabolismo , Valina , Aciltransferases/antagonistas & inibidores , Aminoácidos/farmacologia , Catálise , Fenômenos Químicos , Química , Fabaceae/enzimologia , Plantas Medicinais , Estereoisomerismo , Especificidade por Substrato , Valina/farmacologiaRESUMO
1-Aminocyclopropane-1-carboxylic acid (ACC) is known to be converted to ethylene and conjugated into N-malonyl-ACC in plant tissues. When α-amino[1-(14)C]isobutyric acid (AIB), a structural analog of ACC, was administered to mungbean (Vigna radiata L.) hypocotyl segments, it was metabolized to (14)CO2 and conjugated to N-malonyl-AIB (MAIB). α-Aminoisobutyric acid inhibited the conversion of ACC to ethylene and also inhibited, to a lesser extent, N-malonylation of ACC and D-amino acids. Although the malonylation of AIB was strongly inhibited by ACC as well as by D-amino acids, the metabolism of AIB to CO2 was inhibited only by ACC but not by D-amino acids. Inhibitors of ACC conversion to ethylene such as anaerobiosis, 2,4-dinitrophenol and Co(2+), similarly inhibited the conversion of AIB to CO2. These results indicate that the malonyalation of AIB to MAIB is intimately related to the malonylation of ACC and D-amino acids, whereas oxidative decarboxylation of AIB is related to the oxidative degradation of ACC to ethylene.
RESUMO
When whole unripe green tomato fruits (Lycopersicon esculentum Mill, cv T(3)) were treated with ethylene (10 microliters per liter) for 18 hours, the fruit's ability to convert 1-aminocyclopropane-1-carboxylic acid (ACC) to N-malonyl-ACC (MACC) increased markedly and such an effect was also observed in fruits of mutant nor, which cannot ripen normally. The promotion of the capability to malonylate ACC by ethylene increased with the increasing ethylene concentration from 0.1 to 100 microliters per liter and with increasing duration of ethylene treatment up to 8 hours; a longer duration of ethylene treatment did not further increase the malonylation capability. When ethylene was withdrawn, the promotion disappeared within 72 hours. Norbornadiene, a competitive inhibitor of ethylene action, effectively eliminated the promotive effect of ethylene. Ethylene treatment also promoted the fruits' capability to conjugate d-amino acids and alpha-amino-isobutyric acid. Since the increase in the tissue's capability to malonylate ACC was accompanied by an increase in the extractable activity of ACC and d-amino acid malonyltransferase, ethylene is thought to promote the development of ACC/d-amino acid malonyltransferase in unripe tomato fruits.
RESUMO
We have studied the mechanism of auxin autonomy in tobacco (Nicotiana tabacum L.) crowngall tissues transformed by the auxin-mutant (tms (-)) A66 strain of Agrobacterium tumefaciens. Normally, tms (-) tobacco tumor tissues require the formation of shoots to exhibit auxin-independent growth in culture. We have isolated from tms (-) tobacco cells several stable variants that are fully hormone-independent and grow rapidly as friable, unorganized tissues, thus mimicking the growth and morphology of tms (+) tobacco cells that produce high levels of auxin. However, none of the variants contained the high levels of auxin found in tms (+) tumor cells. The variants could be divided into two classes with respect to their response to applied auxin. The first class was highly sensitive to applied auxin: low concentrations (1 µM) of α-naphthaleneacetic acid (NAA) severely inhibited growth and markedly stimulated the accumulation of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). The second class of variants showed a low sensitivity to applied auxin: growth was promoted by concentrations of NAA up to 10 µM, and growth inhibition and high ACC levels were observed only at high NAA concentrations (100 µM). Unorganized variants with low auxin sensitivity were also isolated from a variant line with high auxin sensitivity. The isolation of tumor cells that exhibited the growth phenotype of tms (+) cells while retaining the low auxin content and low auxin sensitivity of tms (-) cells indicates that full hormone autonomy, characteristic of wild-type crown-gall tumors, can be achieved by a mechanism that is independent of changes in the auxin physiology of the cells.
RESUMO
Nicotiana glutinosa compensated for a mutated tumor-morphology-shooty (tms) (auxin biosynthesis) locus of Agrobacterlum tumefaciens strain A66 and showed the same virulent tumor response to infection by strain A66 or the wild-type strain A6. Cloned cell lines transformed by strains A6 or A66 were fully hormone independent in culture and grew rapidly as friable, unorganized tissues on hormone-free growth medium. Growth of N. glutinosa tumor cells was inhibited by addition of alpha-naphthaleneacetic acid to the growth medium, and A6- and A66-transformed cells showed similar dose responses to this auxin. On the other hand, A6-transformed cells contained much higher levels of indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) than A66-transformed cells. Differences in IAA and ACC levels in N. glutinosa tumor lines were consistent with the expected activity of the tms locus and were quantitatively similar to results obtained previously with A6- and A66-transformed cells of Nicotiana tabacum, which does not compensate for mutated tms genes. Thus, compensation for mutated tms genes in N. glutinosa did not result from increased auxin accumulation and did not appear to be related to the capacity of this host for auxin biosynthesis.
RESUMO
The production of an intracellular secondary metabolite rosmarinic acid (RA) by plant cell suspensions of Anchusa officinalis cultivated with intermittent medium exchange is investigated. Initially, a two-stage perfusion culture method was employed. After being cultured in the batch mode for ca. 6 days in B5 medium plus 3% sucrose, 1 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D), and 0.1 mg/L kinetin (2,4-D B5 medium), Anchusa culture was cultivated to high cell density by perfusion during the growth stage using a hormone-free Gamborg B5 medium supplemented with 6% sucrose. This was followed by a production stage, in which a complete medium exchange into B5 medium plus 3% sucrose and 0.25 mg/L naphthleneacetic acid (NAA) was conducted. The two-stage perfusion culture had a higher maximum culture RA concentration but a lower RA content per cell than the batch stock culture maintained in the 2,4-D B5 medium. Higher culture RA concentration was due primarily to high cell density. The high packed cell volume, however, seemed to reduce the synergistic effect of NAA on RA synthesis. Subsequently, a single-stage perfusion culture method was investigated. The best result was obtained by growing the culture in the batch mode for ca. 10 days using B5 medium supplemented with 3% sucrose and 0.25 mg/L NAA, followed by perfusing the culture with B5 medium plus 6% sucrose and 0.25 mg/L NAA at a constant perfusion rate of 0.1/day. A maximum cell dry weight of 35 g/L and a RA concentration of almost 4 g/L were achieved. This is the highest RA concentration ever reported in the Anchusa culture.
RESUMO
Since 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC), the major conjugate of 1-aminocyclopropane-1-carboxylic acid (ACC) in plant tissues, is a poor ethylene producer, it is generally thought that MACC is a biologically inactive end product of ACC. In the present study we have shown that the capability of watercress (Nasturtium officinale R. Br) stem sections and tobacco (Nicotiana tabacum L.) leaf discs to convert exogenously applied MACC to ACC increased with increasing MACC concentrations (0.2-5 millimolar) and duration (4-48 hours) of the treatment. The MACC-induced ethylene production was inhibited by CoCl(2) but not by aminoethoxyvinylglycin, suggesting that the ACC formed is derived from the MACC applied, and not from the methionine pathway. This was further confirmed by the observation that radioactive MACC released radioactive ACC and ethylene. A cell-free extract, which catalyzes the conversion of MACC to ACC, was prepared from watercress stems which were preincubated with 1 millimolar MACC for 24 hours. Neither fresh tissues nor aged tissues incubated without external MACC exhibited enzymic activity, confirming the view that the enzyme is induced by MACC. The enzyme had a K(m) of 0.45 millimolar for MACC and showed maximal activity at pH 8.0 in the presence of 1 millimolar MnSO(4). The present study indicates that high MACC levels in the plant tissue can induce to some extent the capability to convert MACC to ACC.