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1.
The antagonistic activity of Bacillus subtilis strain G1 was tested against various isolates of Aspergillus flavus in vitro. A talc-based powder formulation of B. subtilis strain G1 was prepared and evaluated to control A. flavus infection and aflatoxin B1 contamination in groundnut under greenhouse and field conditions. The results showed that B. subtilis strain G1 could inhibit the growth of all isolates of A. flavus tested in dual culture assay and the growth inhibition ranged from 93 to 100%. Results of greenhouse and field experiments indicated that B. subtilis strain G1 when applied to groundnut as seed treatment and soil application significantly suppressed A. flavus population in the soil, A. flavus infection and aflatoxin B1 content in kernels and increased the pod yield. These studies show that B. subtilis strain G1 has potential as a biocontrol agent for control of aflatoxin contamination in groundnut.  相似文献   

2.
Arbuscular Mycorrhizal (AM) fungi enhance terrestrial plant growth by forming a symbiotic relationship with the roots of its host plant. A growth stimulant for AM fungi was isolated from a brown alga Laminaria japonica Areschoug. The active substance for in vitro AM hyphal growth was isolated from 75% methanol extracts of L. japonica using a succession of chromatographic procedures, including flash chromatography equipped with an octa decyl silane (ODS) column, gel filtration chromatography and HPLC using an ODS column. Spores of Gigaspora margarita Becker & Hall, an AM fungus, were exposed to the compound in vitro, and hyphal growth of G. margarita was measured after two weeks of incubation. At 40 mg L−1, the compound significantly stimulated the in vitro hyphal growth of G. margarita, compared to the control. This compound was elucidated as 5′-deoxy-5′-methylamino-adenosine by EIMS and NMR spectrum.  相似文献   

3.
Autosomal recessive osteopetrosis (ARO) is a severe genetic bone disease characterized by high bone density due to mutations that affect formation or function of osteoclasts. Mutations in the a3 subunit of the vacuolar-type H+-ATPase (encoded by T-cell immune regulator 1 [TCIRG1]) are responsible for ~50% of all ARO cases. We identified a novel TCIRG1 (c.G630A) mutation responsible for an unusually mild form of the disease. To characterize this mutation, osteoclasts were differentiated using peripheral blood monocytes from the patient (c.G630A/c.G630A), male sibling (+/+), unaffected female sibling (+/c.G630A), and unaffected parent (+/c.G630A). Osteoclast formation, bone-resorbing function, TCIRG1 protein, and mRNA expression levels were assessed. The c.G630A mutation did not affect osteoclast differentiation; however, bone-resorbing function was decreased. Both TCIRG1 protein and full-length TCIRG1 mRNA expression levels were also diminished in the affected patient's sample. The c.G630A mutation replaces the last nucleotide of exon 6 and may cause splicing defects. We analyzed the TCIRG1 splicing pattern between exons 4 to 8 and detected deletions of exons 5, 6, 7, and 5-6 (ΔE56). These deletions were only observed in c.G630A/c.G630A and +/c.G630A samples, but not in +/+ controls. Among these deletions, only ΔE56 maintained the reading frame and was predicted to generate an 85 kDa protein. Exons 5-6 encode an uncharacterized portion of the cytoplasmic N-terminal domain of a3, a domain not involved in proton translocation. To investigate the effect of ΔE56 on V-ATPase function, we transformed yeast with plasmids carrying full-length or truncated Vph1p, the yeast ortholog of a3. Both proteins were expressed; however, ΔE56-Vph1p transformed yeast failed to grow on Zn2+-containing plates, a growth assay dependent on V-ATPase-mediated vacuolar acidification. In conclusion, our results show that the ΔE56 truncated protein is not functional, suggesting that the mild ARO phenotype observed in the patient is likely due to the residual full-length protein expression.  相似文献   

4.
The abundance of Aulacoseira granulata (Ehrenburg) Simonsen and Gloeocystis planctonica (West & G.S.West) Lemmermann was assessed during the summers of 2005 and 2010 in the eutrophic Fox River, Wisconsin, USA. In both years, a mid‐summer bloom of G. planctonica was followed by the rapid growth of A. granulata. Laboratory experiments in which A. granulata was grown in cell‐free filtrate of a G. planctonica culture revealed that the growth of A. granulata was stimulated in the G. planctonica‐treated medium relative to controls. This effect was detected when dormant A. granulata cells were used as the source culture for the experiment but not when actively growing cells were used. Dormant A. granulata also grew more rapidly in river water collected after the 2010 G. planctonica bloom relative to river water collected before the bloom. These results suggest that the summer bloom of A. granulata in the river was stimulated by G. planctonica. This relationship can be described as stimulated rejuvenation, an interaction where the transition of an algal resting stage into active growth is triggered by exposure to another species.  相似文献   

5.
In the presence of 1–5 mM n-butyrate, murine leukemic L1210 cells cease proliferation and become arrested in the G1A compartment of the G1 phase. Cells in this compartment, in comparison with the remaining cells of the G1 phase (G1B), are characterized by low RNA content and more condensed chromatin. During unperturbed growth the cell residence times in G1A are of indeterminate duration (exponentially distributed); the half-time of L1210 cell residence in G1A is about 1.4 h. The effect of n-butyrate in arresting cells in G1A was concentration-dependent. However, the sensitivity of L1210 cells to this drug was markedly enhanced when cells were treated for longer than one generation (12 h). Cells arrested in G1A remained viable and when n-butyrate was removed, after a lag period, they resumed progression through the cycle.The effect of n-butyrate on cell progression through various parts of the cycle was studied in a stathmokinetic experiment. The rate of cell entrance into mitosis was decreased by 30, 60 and 110%, in the presence of 1, 2.5 and 5 mM n-butyrate respectively, thus indicating a slowdown in cell progression through G2 and S. The duration of G2 was prolonged by 20, 70 and 140% at 1, 2.5 and 5 mM n-butyrate respectively. The half-time of cell residence in G1A was increased by as much as 1.5-, 6.3- and 15.6-fold by 1, 2.5 and 5 mM n-butyrate. Progression through late G1 (G1B) was not affected at 1 mM, and could not be estimated at higher drug concentrations. The effects on cell cycle progression were evident 1 h after addition of n-butyrate.DNA in situ in nuclei of n-butyrate-treated cells had lowered (by 2–8 °C) stability to thermal denaturation and increased (by 15%) accessibility to DNase I. The decrease in DNA stability to heat was more pronounced when permealized cells were heated in the presence of 1 mM MgCl2 rather than EDTA. DNA in situ in the nuclei of n-butyrate-treated cells also showed decreased sensitivity to acid-induced denaturation. Changes in chromatin were seen in all cells, regardless of cell cycle phase, within the first hours after addition of n-butyrate. Mitotic cells, however, reacted to n-butyrate more rapidly than interphase cells. The observed changes in L1210 cells are most likely a consequence of histone modifications (acetylation of inner histones, dephosphorylation of histone H1) induced by n-butyrate.  相似文献   

6.
Myostatin, or growth and differentiation factor 8, is a member of the transforming growth factor-β superfamily; it functions as a negative regulator of skeletal muscle development and growth in mammals. In this study, single nucleotide polymorphisms in the 5′ regulatory region and exon 1 of the myostatin gene were detected by PCR–SSCP in the Bian, Jinghai, Youxi, and Arbor Acre chickens, and the associations of the polymorphisms with reproduction traits were analyzed. Seven SNPs (A326G, C334G, C1346T, G1375A, A1473G, G1491A, and G2283A) were found in the myostatin gene. Association analysis showed that the G2283A were significantly associated with reproduction traits. Bian chickens of the GG genotype had a greater age at first egg than those of the GA and AA genotypes (P < 0.01). Correspondingly, Bian chickens of the GA and AA genotypes had larger egg number at 300 days than those of the GG genotype (P < 0.05 and P < 0.01, respectively). Bian chickens of the AA genotype had significantly higher body weight at 300 days than those of the GG genotype (P < 0.05). These results suggested that the myostatin gene may have certain effects on reproduction traits other than merely as a negative regulator of skeletal muscle development and growth in mammals previously reported.  相似文献   

7.
Summary Four mouse B16 melanoma subclones representing distinct stages in the benign-to-malignant progression of that tumor (G3.15, G3.5, G3.12, and G3.26), and three phenotype conversion variants with enhanced malignancy (G3.15*, G3.5*, and G3.12*), were comparatively examined for exogenous mitogen and growth factor requirements and for responsiveness to exogenous and endogenous growth modulators in monolayer culture. Growth behavior in serum-free medium with or without mitogen or growth factor supplements, and in supplemented quiescent serum-containing medium, confirmed previous indications that the G3.5 and G3.15* phenotypes were identical, as were the G3.26 and G3.12* phenotypes. However, G3.12 differed from the closest conversion equivalent, G3.5*, and probably represents an aberrant phenotype within this sequence. There was a direct relationship between degree of malignancy (G3.15 → G3.5 → G3.5* → G3.26), growth capacity in serum-free medium, and responsiveness to transferrin. Only G3.5*, G3.26, and G3.12* cells were growth-autonomous in serum-free medium and also highly responsive to mitogens. The polypeptide growth factors epidermal growth factor, platelet-derived growth factor, basic fibroblast growth factor, transforming growth factor-α, and insulinlike growth factor-1 and -2 were generally stimulatory in quiescent medium, but the degree of growth promotion was unrelated to malignancy level. Transforming growth factor-β1 was inhibitory to the more benign populations (G3.15, G3.5, and G3.15*) but stimulated proliferation of other cells. All populations produced autocrine fibronectin, and G3.12, G3.5*, G3.26, and G3.12* cells also produced autocrine transferrin. Only G3.12 cells failed to utilize both of those factors. Reversible mitogen-stimulated G3.12 cell growth was accompanied by partial and reversible responsiveness to both autocrine transferrin and fibronectin, whereas permanent stimulation by both factors characterized all growth-autonomous populations.  相似文献   

8.
Arthrobacter sp. strain G1 is able to grow on 4-fluorocinnamic acid (4-FCA) as sole carbon source. The organism converts 4-FCA into 4-fluorobenzoic acid (4-FBA) and utilizes the two-carbon side-chain for growth with some formation of 4-fluoroacetophenone as a dead-end side product. We also have isolated Ralstonia sp. strain H1, an organism that degrades 4-FBA. A consortium of strains G1 and H1 degraded 4-FCA with Monod kinetics during growth in batch and continuous cultures. Specific growth rates of strain G1 and specific degradation rates of 4-FCA were observed to follow substrate inhibition kinetics, which could be modeled using the kinetic models of Haldane–Andrew and Luong–Levenspiel. The mixed culture showed complete mineralization of 4-FCA with quantitative release of fluoride, both in batch and continuous cultures. Steady-state chemostat cultures that were exposed to shock loadings of substrate responded with rapid degradation and returned to steady-state in 10–15 h, indicating that the mixed culture provided a robust system for continuous 4-FCA degradation.  相似文献   

9.
SNF1 of Saccharomyces cerevisiae is an essential gene for the derepression of glucose repression. A homolog of SNF1 (CtSNF1) was isolated from an n-alkane-assimilating diploid yeast, Candida tropicalis. CtSNF1 could complement the snf1 mutant of S. cerevisiae. The previously published method for introducing the exogenous DNA into C. tropicalis was employed to construct SNF1/ snf1 heterozygote and snf1/snf1 homozygote strains. The successfully constructed SNF1/snf1 heterozygote was named KO-1. Disruption of the second CtSNF1 allele was unsuccessful, suggesting that CtSNF1 might be essential for cell viability. Therefore, in order to control the expression of CtSNF1, a strain (named KO-1G) in which the promoter region of CtSNF1 was replaced with the GAL10 promoter of C. tropicalis was constructed, and the growth of strains KO-1 and KO-1G was compared with that of the parental strain. The growth of strain KO-1 on glucose, sucrose, or acetate did not differ from the growth of the parental strain, but strain KO-1 showed a slight growth retardation on n-alkane. The growth of strain KO-1G on galactose was normal, but the cells stopped growing when transferred to glucose-, acetate-, or n-alkane-containing medium. Northern blot analysis against mRNA from the n-alkane-grown KO-1G strain demonstrated a close relationship between the presence of CtSNF1 mRNA and the growth of the cells, indicating that CtSNF1 is essential for cell viability. Moreover, mRNA levels of isocitrate lyase, which is localized in peroxisomes of C. tropicalis, were significantly affected by the level of CtSNF1 mRNA. Received: 3 May 1999 / Accepted: 14 July 1999  相似文献   

10.
Mucor circinelloides, a dimorphic opportunistic pathogen, expresses three heterotrimeric G‐protein beta subunits (Gpb1, Gpb2 and Gpb3). The Gpb1‐encoding gene is up‐regulated during mycelial growth compared with that in the spore or yeast stage. gpb1 deletion mutation analysis revealed its relevance for an adequate development during the dimorphic transition and for hyphal growth under low oxygen concentrations. Infection assays in mice indicated a phenotype with considerably reduced virulence and tissue invasiveness in the deletion mutants (Δgpb1) and decreased host inflammatory response. This finding could be attributed to the reduced filamentous growth in animal tissues compared with that of the wild‐type strain. Mutation in a regulatory subunit of cAMP‐dependent protein kinase A (PKA) subunit (PkaR1) resulted in similar phenotypes to Δgpb1. The defects exhibited by the Δgpb1 strain were genetically suppressed by pkaR1 overexpression, indicating that the PKA pathway is controlled by Gpb1 in M. circinelloides. Moreover, during growth under low oxygen levels, cAMP levels were much higher in the Δgpb1 than in the wild‐type strain, but similar to those in the ΔpkaR1 strain. These findings reveal that M. circinelloides possesses a signal transduction pathway through which the Gpb1 heterotrimeric G subunit and PkaR1 control mycelial growth in response to low oxygen levels.  相似文献   

11.
外来种粗毛牛膝菊在秦巴山区的种群发展动态   总被引:1,自引:0,他引:1  
刘刚  张璐璐  孔彬彬  卫欣华  朱志红 《生态学报》2016,36(11):3350-3361
外来种能否成功入侵新生境取决于其自身入侵特性(快速生长、足够的繁殖体压力等)和环境因子的作用。原产于热带美洲的粗毛牛膝菊(Galinsoga quadriradiata Ruizpav.)在秦巴山区呈现快速爆发趋势,但其种群发展动态尚不明确。通过监测实验和野外调查,对粗毛牛膝菊种群动态和其对入侵地环境选择的偏好性规律进行了研究。在4块样地中开展的监测研究显示,粗毛牛膝菊种群密度最高可达300株/m~2,单株平均种子产量达675粒,单位面积的种子产量达45619株/m~2,说明其在研究地区已能够产生较大规模的稳定增长的种群,可为种群爆发提供较高的繁殖体压力;其种群密度随着时间呈逻辑斯蒂型下降趋势,且在向繁殖阶段过渡期间个体死亡率最高,暗示着种群可能存在负密度制约效应;对秦巴山区30个野外样地的调查研究显示,粗毛牛膝菊主要入侵农田、撂荒地、路边等受到过人为活动干扰的生境;其在群落中出现的频度与土壤紧实度显著正相关,而与坡度显著负相关,表现出对入侵地环境因子的偏好性。调查结果说明,在这些干扰生境中,粗毛牛膝菊种群更容易在土壤紧实度高、坡度小的地段建立,这将为进一步预测其入侵趋势提供依据。  相似文献   

12.
Saccharomyces cerevisiae Cdc7 kinase is required for initiation of S phase, and its kinase activity, which is positively regulated by Dbf4 protein, reaches maximum at the G1/S boundary. In this study, we constructed Cdc7 point mutants (T281E, T281A, D182N, D163N, and T167E) and examined the effect of each mutant on growth. All the mutants lost the ability to complement temperature-sensitive growth of cdc7(ts) mutants at a low protein level, whereas T281A (putative target of phosphorylation) and T167E (residue involved in substrate recognition) restored the growth of cdc7(ts) when overproduced to a high level. Three putative kinase-negative mutants (T281E, D182N, and D163N) inhibited growth when overexpressed in a wild-type strain. Analyses of DNA content and morphology revealed that most cells were arrested as dumbbells with 1C DNA, indicative of a block in the G1 to S transition. This growth inhibition was suppressed by co-overexpression of the wild-type Cdc7 or Dbf4 protein. Furthermore, deletion of the Dbf4 protein-binding region in each Cdc7 mutant resulted in loss of growth inhibitory effect. Thus, dominant-negative effects of T281E, D182N, and D163N on growth can be best explained by inactivation of the wild-type Cdc7 function through titration of Dbf4 by these inactive kinases. Our results are consistent with the notion that association of Dbf4 with Cdc7 is essential for the G1 to S transition in S. cerevisiae. Received: 17 September 1996 / Accepted: 6 January 1997  相似文献   

13.
The mean lengths of G1, S, G2 and M phases of the cell cycle were determined on the basis of the population distribution ofCandida utilis grown in a continuous culture under steady-state conditions by using an original mathematical method. The length of the G2 phase was proportional to that of G1; the length of M was effectively independent of the growth rate. The length of S was proportional to the mean number of mitochondria in the cell.  相似文献   

14.
Gymnodinium smaydae is one of the fastest growing dinoflagellates. However, its population dynamics are affected by both growth and mortality due to predation. Thus, feeding by common heterotrophic dinoflagellates Gyrodinium dominans , Gyrodinium moestrupii , Oblea rotunda , Oxyrrhis marina , and Polykrikos kofoidii , and the naked ciliate Pelagostrobilidium sp. on G. smaydae was investigated in the laboratory. Furthermore, growth and ingestion rates of O. marina , G. dominans , and Pelagostrobilidium sp. on G. smaydae in response to prey concentration were also determined. Oxyrrhis marina , G. dominans , G. moestrupii , and Pelagostrobilidium sp. were able to feed on G. smaydae , but P. kofoidii and O. rotunda did not feed on this dinoflagellate. The maximum growth rate of O. marina on G. smaydae was 0.411 per day. However, G. smaydae did not support the positive growth of Pelagostrobilidium sp. The maximum ingestion rates of O. marina and Pelagostrobilidium sp. on G. smaydae were 0.27 and 6.91 ng C · predator?1 · d?1, respectively. At the given mean prey concentrations, the highest growth and ingestion rates of G. dominans on G. smaydae were 0.114 per day and 0.04 ng C · predator?1 · d?1, respectively. The maximum growth and ingestion rates of O. marina on G. smaydae are lower than those on most of the other algal prey species. Therefore, O. marina may be an effective predator of G. smaydae , but G. smaydae may not be the preferred prey for supporting high growth of the predator in comparison to other species as inferred from a literature survey.  相似文献   

15.
16.
17.
The Saccharomyces cerevisiae ALG7 gene, which functions by initiating the dolichol pathway of protein N-glycosylation, displays properties of an early growth-response gene. To initiate studies of the involvement of ALG7 in cellular proliferation, we have now more precisely analyzed ALG7 expression in the G1 phase of cell cycle. We show that the rapid rate of ALG7 mRNA accumulation following growth stimulation was attenuated soon thereafter and that ALG7 growth induction occurred irrespective of α-factor. ALG7 growth induction was observed in mutants conditionally defective for reentry into the cell cycle from the stationary phase, indicating that the induction occurred prior to the performance of START. In addition, the steady-state levels of ALG7 mRNAs declined four-fold in response to START-I cell division arrest brought about by α-factor treatment later in G1. Importantly, deregulated expression of ALG7 resulted in an aberrant α-factor response. Our data not only indicate that ALG7 expression is regulated at two critical control points in G1 that determine the proliferative potential of cells, but also provide a link between ALG7 and START.  相似文献   

18.
Steviol glycosides (SGs) are extracted from Stevia leaves for use as a natural sweetener. Among SGs, stevioside is most abundant in leaf extracts followed by rebaudioside A (Reb A). However, Reb A is of particular interest because of its sweeter and more pleasant taste compared to stevioside. Therefore, the development of new Stevia varieties with a higher Reb A to stevioside ratio would be desirable for the production of higher quality natural sweeteners. Here, we generated transgenic Stevia plants overexpressing Stevia UDP‐glycosyltransferase 76G1 (SrUGT76G1) that is known to convert stevioside to Reb A through 1,3‐β‐d ‐glucosylation in vitro. Interestingly, by overexpressing SrUGT76G1, the Reb A to stevioside ratio was drastically increased from 0.30 in wild‐type (WT) plants up to 1.55 in transgenic lines without any significant changes in total SGs content. This was contributed by a concurrent increase in Reb A content and a decrease in stevioside content. Additionally, we were able to find an increase in the Reb C to dulcoside A ratio in transgenic lines. Using the glutathione S‐transferase‐tagged SrUGT76G1 recombinant protein for an in vitro glucosyltransferase assay, we further demonstrated that Reb C can be produced from the glucosylation of dulcoside A by SrUGT76G1. Transgenic Stevia plants having higher Reb A to stevioside ratio were visually indistinguishable from WT plants. Taken together, our results demonstrate that the overexpression of SrUGT76G1 in Stevia is an effective way to generate new Stevia varieties with higher proportion of the more preferred Reb A without compromising on plant development.  相似文献   

19.
Achondroplasia is the most common form of dwarfism and has an incidence of approximately 1/7500. In more than 97% of cases, it is caused by a recurrent point mutation, a G to A substitution at nucleotide position 1138 (G1138A) of the fibroblast growth factor receptor 3 gene. Although this is an autosomal dominant condition, more than 90% of all mutations occur sporadically making this one of the most mutagenic sites in the human genome. The reasons for the high spontaneous G1138A mutation rate are not known. This investigation was performed by developing a simple and rapid semi-quantitative allele specific PCR based assay capable of reliably detecting more than 25 mutant G1138A copies in a pool of 300 000 wild type molecules. Using this assay, the G1138A mutation frequency was measured in cell lines deficient in mismatch repair (LoVo, SW48) and comparing it with controls. No differences were found in the frequency of this point mutation between the mismatch repair deficient and wild type cell lines.__________From Genetika, Vol. 41, No. 8, 2005, pp. 1137–1141.Original English Text Copyright © 2005 by Grewal.This article was submitted by the author in English.  相似文献   

20.
A pot trial using Glomus mosseae along with EDTA (ethylenediaminetetraacetic acid) was conducted for the phytoextraction of cadmium (Cd) by celery (Apium graveolens Linn.) plants from soil artificially contaminated with Cd under glass house conditions. The experiment is a 2 × 2 × 4 factorial design with two levels of G. mosseae inoculations (G. mosseae inoculated and uninoculated), two EDTA concentrations (without and with 2.5 mmol kg?1 soil EDTA) and four Cd concentrations (0, 5, 10, and 20 mg kg?1 soil). The results indicate the formation of an effective symbiosis between G. mosseae and celery in the contaminated soil. However, an increase in Cd input level and EDTA addition showed strong phytotoxic effect on celery plants and G. mosseae, as a considerable decrease in the frequency of root colonization and spore density was noticed. However, the plants were able to withstand the stressed condition due to the benefits provided by G. mosseae through increased P accumulation, chlorophyll content, and plant growth, resulting in an increase in Cd accumulation, which was good enough for the phytoextraction purpose. Thus, celery plants inoculated with G. mosseae and later supplemented with EDTA could be an effective and potentially suitable practice for the remediation of Cd-contaminated sites.  相似文献   

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