bluuebunny/crossref_metadata_2025_split huggingface dataset:
LuxS controls bacteriocin production in Streptococcus mutans through a novel regulatory component
Authors: Merritt Justin , Kreth Jens , Shi Wenyuan , Qi Fengxia 
Published: July 2005

SummaryThe oral pathogen Streptococcus mutans employs a variety of mechanisms to maintain a competitive advantage over many other oral bacteria which occupy the same ecological niche. Production of the bacteriocin, mutacin I, is one such mechanism. However, little is known about the regulatory mechanisms associated with mutacin I production. Previous work has demonstrated that the production of mutacin I greatly increased with cell density. In this study, we found that high cell density also triggered high level mutacin I gene transcription. However, this response was abolished upon deletion of luxS. Further analysis using real‐time reverse transcription polymerase chain reaction (RT‐PCR) demonstrated that in the luxS mutant transcription of both the mutacin I structural gene mutA and the mutacin I transcriptional activator mutR was impaired. Through microarray analysis, a putative transcription repressor annotated as Smu1274 in the Los Alamos National Laboratory Oral Pathogens Sequence Database was identified, which was strongly induced in the luxS mutant. Characterization of Smu1274, which we referred to as irvA, suggested that it may act as an inducible repressor to suppress mutacin I gene expression. A luxS and irvA double mutant regained the ability to produce mutacin I; whereas a constitutive irvA‐producing strain was impaired in mutacin I production. These findings reveal a novel regulatory pathway for mutacin I gene expression, which may provide clues to the regulatory mechanisms of other cellular functions regulated by luxS in S. mutans.
Defining the genetic differences between wild and domestic strains of Bacillus subtilis that affect poly‐γ‐dl‐glutamic acid production and biofilm formation
Authors: Stanley Nicola R. , Lazazzera Beth A. 
Published: July 2005

SummaryBiofilms are communities of microbial cells that are encased in a self‐produced, polymeric matrix and  are  adherent  to  a  surface.  For  several  species of bacteria, an enhanced ability to form biofilms has been linked with an increased capability to produce exopolymers. To identify exopolymers of Bacillus subtilis that can contribute to biofilm formation, we transferred the genetic determinants that control exopolymer production from a wild, exopolymer‐positive strain to a domesticated, exopolymer‐negative strain. Mapping these genetic determinants led to the identification of γ‐poly‐dl‐glutamic acid (γ‐PGA) as an exopolymer that increases biofilm formation, possibly through enhancing cell–surface interactions. Production of γ‐PGA by Bacillus subtilis was known to be dependent on the two‐component regulator ComPA; this study highlighted the additional dependence on the DegS‐DegU, DegQ and SwrA regulator proteins. The inability of the domestic strain of B. subtilis to produce γ‐PGA was mapped to two base pairs; a single base pair change in the promoter region of degQ and a single base pair insertion in the coding region of swrA. Introduction of alleles of degQ and swrA from the wild strain into the domestic strain was sufficient to allow γ‐PGA production. In addition to controlling γ‐PGA production, ComPA and DegSU were also shown to activate biofilm formation through an as yet undefined pathway. The identification of these regulators as affecting γ‐PGA production and biofilm formation suggests that these processes are regulated by osmolarity, high cell density and phase variation.
Multiple drug resistance genes in malaria – from epistasis to epidemiology
Authors: Duraisingh Manoj T. , Refour Philippe 
Published: July 2005

SummaryA decline in our ability to successfully treat patients with malaria infections of the parasitic protozoan Plasmodium falciparum with cheap quinoline drugs has led to a huge escalation in morbidity and mortality in recent years. Many approaches have been taken, including classical genetics, reverse genetics and molecular epidemiology, to identify the molecular determinants underlying this resistance. The contribution of the P. falciparum multidrug resistance gene, pfmdr1, to antimalarial resistance has been a source of controversy for over a decade since it was first identified. In the current issue of Molecular Microbiology, Sidhu and colleagues use powerful reverse genetics to demonstrate the importance of commonly occurring alleles of pfmdr1 in conferring resistance to the second‐line drugs quinine and sensitivity to the new alternatives mefloquine and artemisinin. They also elegantly highlight the importance of genetic background and epistasis between pfmdr1 and other potential modulators of drug resistance. Such molecular knowledge will facilitate surveillance/monitoring and aid the development of strategies for the reversal of resistance.
Frp1 is a Fusarium oxysporum F‐box protein required for pathogenicity on tomato
Authors: Duyvesteijn Roselinde G. E. , Van Wijk Ringo , Boer Yvonne , Rep Martijn , Cornelissen Ben J. C. , Haring Michel A. 
Published: July 2005

Summary Fusarium oxysporum f. sp. lycopersici is the causal agent of tomato wilt disease. In order to identify genes involved in its pathogenicity, we performed insertional mutagenesis. Mutant N40 had lost its pathogenicity completely, when tested in bioassays with tomato seedlings. Molecular characterization of mutant N40 revealed that the plasmid insertion had occurred in a gene that codes for a 60.2 kDa protein containing an F‐box motif. The gene was therefore designated as FRP1 (F‐box protein required for pathogenicity). Targeted FRP1 disruptants had lost their pathogenicity completely, and became fully virulent again upon re‐introduction of the FRP1 gene. This confirmed that the FRP1 gene is required for pathogenesis. In a yeast two‐hybrid assay Frp1 interacts with Skp1, suggesting involvement of an SCF ubiquitin ligase complex in pathogenicity. FRP1 is constitutively expressed during infection and under different culture conditions. Although growth, spore formation and germination on artificial media were not impaired, confocal laser scanning microscopy of a GFP‐marked mutant N40 and a GFP‐marked targeted FRP1 disruptant revealed that they were unable to colonize the roots.
A new mechanism for chloramphenicol, florfenicol and clindamycin resistance: methylation of 23S ribosomal RNA at A2503
Authors: Kehrenberg Corinna , Schwarz Stefan , Jacobsen Lene , Hansen Lykke H. , Vester Birte 
Published: July 2005

SummaryThe gene product of cfr from Staphylococcus sciuri confers resistance to chloramphenicol, florfenicol and clindamycin in Staphylococcus spp. and Escherichia coli. Cfr is not similar to any other known chloramphenicol resistance determinant. Comparative investigation of E. coli with and without a plasmid‐encoded Cfr showed a decreased drug binding to ribosomes in the presence of Cfr. As chloramphenicol/florfenicol and clindamycin have partly overlapping drug binding sites on the ribosome, the most likely explanation is that Cfr modifies the RNA in the drug binding site. This hypothesis was supported by drug footprinting data that showed both a decreased drug binding and an enhanced reverse transcriptase stop at position 2504, which corresponds to a modification at position A2503 at the drug binding site. A 45 n long RNA fragment containing the appropriate region was isolated and MALDI‐TOF mass spectrometry in combination with tandem mass spectrometry showed an additional methylation at position A2503. Moreover, reduced methylation was detected at nucleotide C2498. The results show that Cfr is an RNA methyltransferase that targets nucleotide A2503 and inhibits ribose methylation at nucleotide C2498, thereby causing resistance to chloramphenicol, florfenicol and clindamycin.
Protein phosphorylation is a prerequisite for intracellular Ca2+release and ion channel control by nitric oxide and abscisic acid in guard cells
Authors: Sokolovski Sergei , Hills Adrian , Gay Rob , Garcia‐Mata Carlos , Lamattina Lorenzo , Blatt Michael R. 
Published: July 2005

SummaryRecent work has indicated that nitric oxide (NO) and its synthesis are important elements of signal cascades in plant–pathogen defence, and are a prerequisite for drought and abscisic acid (ABA) responses inArabidopsis thalianaandVicia fabaguard cells. NO regulates inward‐rectifying K+channels and Cl−channels ofViciaguard cells via intracellular Ca2+release. However, its integration with related signals, including the actions of serine–threonine protein kinases, is less well defined. We report here that the elevation of cytosolic‐free [Ca2+] ([Ca2+]i) mediated by NO in guard cells is reversibly inhibited by the broad‐range protein kinase antagonists staurosporine and K252A, but not by the tyrosine kinase antagonist genistein. The effects of kinase antagonism translate directly to a loss of NO‐sensitivity of the inward‐rectifying K+channels and background (Cl−channel) current, and to a parallel loss in sensitivity of the K+channels to ABA. These results demonstrate that NO‐dependent signals can be modulated through protein phosphorylation upstream of intracellular Ca2+release, and they implicate a target for protein kinase control in ABA signalling that feeds into NO‐dependent Ca2+release.
Meiotic chromosome behaviour in an allotriploid derived from an amphidiploid × diploid mating in Cucumis
Authors: Qian C.‐T. , Jahn M. M. , Staub J. E. , Luo X. D. , Chen J. F. 
Published: July 2005

AbstractA synthetic amphidiploid species Cucumis hyriviis Chen & Kirkbride (2n = 4x = 38; genome designated as HHCC) has recently been created from an interspecific mating between C. sativus L. (2n = 2x = 14: genome designated as CC) and C. hystrx. Chakr. (2n = 2x = 24; genome designated as HH). This amphidiploid is resistant to root knot nematode, tolerant to low irradiance, and has higher nutritional value than standard processing cucumber cultivars. An allotriploid (2n = 3x = 26; HCC) was derived from a cross between C. sativus L. and C. hytivus Chen & Kirkbride. Diploid meiotic behaviour in C. sativus and C. hystrix involves the development of seven and 12 metaphase bivalents respectively. In the derived allotriploid. univalents. bivalents, and trivalents (at relatively low frequency) were observed at metaphase I indicating that some homeologues from the C and H genomes can synapse. Based on a comparative karyotype analysis of cucumber (i.e. chromosome size and pairing behaviour) and aliotriploid plants, the seven bivalents observed at metaphase I were ascertained to be cucumber homologues, while the 12 univalents were of C. hystrix origin thus confirming the allotriploid karyotypic constitution to be HCC. On average, the frequency of trivalents was 0.24 at diakinesis and 0.22 in 100 meiocytes at metaphase I. indicating the possibility of genetic exchange due to the homoeology between the C and H genomes. After simultaneous cytokinesis, only polyads were observed in pollen mother cells (PMCs) at telophase II, which led to the production of sterile pollen grains. Multi‐polarization of chromosomes was dominant at anaphase II. However. in about 20% PMCs. chromosomes separated to form a 7C + 1‐2H complement, suggesting a possible method for the production of alien addition cucumber‐C hystrix lines through further backcrossing of the allotriploid to diploid cucumber.
Inheritance of sesquiterpene carboxylic acid synthesis in crosses of Lycopersicon hirsutum with insect‐susceptible tomatoes
Authors: Frelichowski J. E. , Juvik J. A. 
Published: July 2005

AbstractSesquiterpene carboxylic acids (SCA) from Lycopersicon hirsutum f. typicum Humb, & Bonpl, accession LA 1777 confer host‐plant resistance to Helicoverpa zea (Boddie) and Spodoptera exigua (Hübner), two Lepidopteran (Noctuidae) insect pests of the cultivated tomato. L. esculcntum Mill. Hybrids were made between LA 1777 and two accessions of insect‐susceptible tomatoes that do not produce SCA, L. hirsutum LA 1033 and the L. L. esculentum cultivar Chico III, F2 and backcross progeny of both crosses were evaluated for variation in amounts of total SCA in replicated field and greenhouse plantings. Analysis of variance of total SCA in a set of F2 plants of the cross LA 1033 × LA 1777 demonstrated significant variation in SCA attributable to genotype, environment and their interaction. Segregation for high levels of SCA in the populations suggests polygenic inheritance. Broad sense heritability was 0.84, which indicates that phenotypic selection for plants with high SCA is feasible in a backcross‐breeding programme for the introgression of SCA‐mediated insect resistance into tomato cultivars.
Breeding for the improvement of the ideal plant type of sesame
Authors: Baydar H. 
Published: July 2005

AbstractThe objective of this study was to improve the ideal type of sesame, by performing pedigree selection applied to segregating generations of crosses of genotypes with contrasting characters. In the segregating F2 population, the progeny were classified into eight types according to the combinations of carpel number per capsule, capsule number per axil and branching habit. Progeny of individual F2 plants including a particular type were advanced to the F6 generation. It was possible to improve the lines with eight types at the end of the selection process. Some types, especially bicarpels, monocapsule, branch (BMB) and bicarpels, tricapsules, branch (BTB), were considered as ideal plant types in breeding for high‐yielding varieties. While the low‐yielding type quadricarpels, tricapsules, non‐branch (QTN) was the highest in oil content (49.3%), the high‐yielding type BMB was the lowest (43.2%), Although the QTN‐type had the lowest content of oleic acid (41.3%) and the highest content of linoleic acid (43.1 %), the bicarpels, monocapsule, non‐branch (BMN) type had the highest content of oleic acid (48.4%) and the lowest content of linoleic acid (36.6%), Total tocopherol varied between 175.6 and 368.9 mg/kg in the seed oil of the sesame types. The best high‐yielding type BMB was one of the types containing less tocopherol.
Relationships between hard‐seededness and seed weight in mungbean (Vigna radiata) assessed by QTL analysis
Authors: Humphry M. E. , Lambrides C. J. , Chapman S. C. , Aitken E. A. B. , Imrie B. C. , Lawn R. J. , Mcintyre C. L. , Liu C. J. 
Published: July 2005

AbstractWeather damage reduces the value of commercial mungbean. but hard‐seededness can reduce the level of damage. However. attempts lo breed large‐ and hard‐seeded mungbean varieties have been unsuccessful. To understand the relationship between seed weight and hard‐seededness. these trails were investigated using a quantitative trail loci (QTL) mapping approach with a recombinant inbred population derived from a cross between a completely soft‐seeded variety and a completely hard‐seeded genotype. The two parental genotypes also had a sixfold difference in seed weight. QTL analyses revealed four loci for hard‐seededness and 11 loci for seed weight. Two of the hard‐seeded ness loci co‐localized with seed weight QTL. When seed weight was used as a covariate in the analysis of hard‐seededness from the field data, two of the four hard‐seeded QTL remained significant with the effect al one of these remaining unchanged. These results explain why retaining hard‐seededness in large seeded mungbean lines has been unsuccessful. The existence of a persistent locus, however. indicated that breeding large and persistently hard‐seeded varieties of mungbean may be possible.
Development of cytoplasmic‐genic male sterility in safflower
Authors: Anhani K. 
Published: July 2005

AbstractAn interspecific cross was made between Carthamaus oxyacantha and the cultivated species C. tinctorius to develop a cytoplasmic‐genic male sterility (CMS) system in safflower. C. oxyacantha was the donor of sterile cytoplasm. The 3: 1 segregation pattern observed in BC1F2 suggested single gene control with dominance of male‐fertility over male‐sterility. The information obtained from crossing male sterile X male fertile plants in BC1F3 and BC1F4 generations showed statistically significant single gene (1: 1) segregation for male sterility vs. male fertility. The results demonstrated that C. tinctorius possesses a nuclear fertility restorer gene and that a single dominant allele restored fertility (Rf) in progeny carrying CMS cytoplasm of C. oxyacantha. Male sterility occurred with the homozygous recessive condition (rfrf) in a sterile C. oxyacantha cytoplasm background and not in the normal cytoplasm of C. tinctorius. The genetic background of different restorer lines of C. tinctorius having normal cytoplasm did not effect fertility restoration. The absence of male sterile plants in C. tinctorius populations ruled out the possibility of genetic male sterility. Normal meiosis in F1 and BC1F2 ruled out a cytogenetic basis for the occurrence of male sterility.
Genetic variation between Spanish and American versions of sweet corn inbred lines
Authors: Revilla P. , Abuin M. C. , Malvar R. A. , Soengas P. , Ordás B. , Ordás A. 
Published: July 2005

AbstractConservation of maize inbred lines in different stations causes variability among strains. The objective of this research was to determine agronomic and molecular differences in American sweet corn inbreds maintained in Spain. American and Spanish strains of five sweet corn inbred lines were characterized by using 34 RAPD primers that produced 168 consistent bands. Strains of four of these inbreds were crossed in a diallel design, and hybrids were evaluated in four environments in northwestern Spain. The RAPD characterization showed no differences between strains for two inbreds, while divergence between strains was largest for the inbred 15125. Most primers did not reveal any variability between pairs of strains, while some primers produced variations at high rates. Differences in agronomic performance among Spanish and American strains were most important for P51, followed by P39, while strains 1453 or 15125 were not significantly different. Molecular differences between strains were not related to agronomic performance. Residual heterozygosity or outcrossing cannot explain these results. Lack of adaptation could have caused stress‐induced mutagenesis. Natural selection could have eliminated unfavourable selective mutations, but neutral mutations can be found at the molecular level and favourable mutations could have been selected at the agronomic level.
Chromosomal location of powdery mildew resistance gene Pm16 in wheat using SSR marker analysis
Authors: Chen X. M. , Luo Y. H. , Xia X. C. , Xia L. Q. , Chen X. , Ren Z. L. , He Z. H. , Jia J. Z. 
Published: July 2005

AbstractThe use of resistant cultivars is a most economical way to control powdery mildew (Blumeria graminis f.sp. tritici) in wheat (Triticum aestivum L.). Identification of molecular markers closely linked to resistance genes can greatly increase the efficiency of pyramiding resistance genes in wheat cultivars. The objective of this study was to identify molecular markers closely linked lo the powdery mildew resistance gene Pm16. An F2 population with 156 progeny was produced from the cross‘Chancellor’(susceptible) ×‘70281’ (resistant), A total of 45 SSR markers on chromosomes 4A and 5B of wheat and 15 SSRs on chromosome 3 of rice was used lo lest the parents, as well as the resistant and susceptible bulks: the resulting polymorphic markers were used to genotype the F2 progeny. Results indicated that the SSR marker Xgwm159, located on the short arm of chromosome 5B, is closely linked to Pm16 (genetic distance: 5.3 CM). The cytogenetical data presented in an original report, in combination with this molecular analysis, suggests that Pm16 may he located on a translocated 4A.5BS chromosome.
Response to Mycosphaerella pinodes in a germplasm collection of Pisum spp
Authors: Fondevilla S. , ÅVila C. M. , Cubero J. I. , Rubiales D. 
Published: July 2005

AbstractLittle resistance against Mycosphaerella pinodes is available in pea. In this work 78 accessions of Pisum were screened for resistance to M. pinodes. Fourteen accessions showed a good level of resistance in seedlings under controlled conditions, and in mature plants in the field. The highest levels of resistance were found in P. fuivum, followed by P. sativum ssp. eiatius and P. sativum ssp. syriacum. Resistance of five selected accessions was effective against different isolates of M. pinodes originating from different countries. Resistant accessions reported in this paper have been successfully hybridized with field pea cultivars.
Usefulness of the addition of metformin to insulin in pediatric patients with type 1 diabetes mellitus
Authors: Urakami Tatsuhiko , Morimoto Shigeo , Owada Misao , Harada Kensuke 
Published: July 2005

Abstract
Background
: The aim of this study was to evaluate the effect of metformin in addition to insulin therapy in adolescents and young adults with type 1 diabetes mellitus.
Methods
: Nine patients, two males and seven females, aged 18.1 ± 3.0 years, with type 1 diabetes mellitus were studied. They were relatively overweight with a body mass index (BMI) of 24.2 ± 1.8 and had high levels of HbA1c at 9.5 ± 1.2% despite high doses of insulin of 74.0 ± 31.2 U/day. Metformin at the dose of 500–750 mg daily was administered to the patients in addition to insulin therapy for 1 year.
Results
: HbA1c, BMI and insulin dose were compared before 1 year without metformin therapy, at baseline, and at 3, 6 and 12 months during the use of metformin in addition to insulin therapy. HbA1c lowered (8.6 ± 1.4**, 8.4 ± 1.3**, 8.4 ± 1.2*%), BMI was reduced (23.9 ± 1.7*, 23.8 ± 1.8, 23.5 ± 1.8*), and insulin requirement decreased (69.8 ± 29.7*, 68.7 ± 29.8**, 67.3 ± 29.1**U/d) significantly after the start of metformin therapy (*P < 0.05, **P < 0.01 vs at baseline). There were no adverse events, not even lactic acidosis, during the study period.
Conclusion
: Metformin is safe and may represent a useful adjunct to the management of type 1 diabetes mellitus in adolescents and young adults who have poor glycemic control despite a large amount of insulin.
Is leptin a predictive factor in the end of therapy response in chronic hepatitis B?
Authors: Selimo}lu Mukadder Ayle , Ertekin Vildan 
Published: July 2005

Abstract
Background
: The purpose of this study was to determine the leptin levels in children with chronic hepatitis B virus (HBV) infection, and to evaluate the effect of serum leptin levels on the end of therapy response (ETR). It is known that leptin stimulates T‐cell immunity and so T‐cell mediated immune response is critical in the outcome of chronic HBV infection.
Methods
: Leptin levels in children with chronic HBV infection were investigated and its effects on the ETR in 24 children who were treated with interferon‐α and lamivudine combination therapy were evaluated.
Results
: The mean leptin level of the patients was higher than that of healthy children (P = 0.034). Of the patients, seven (29.2%) had ETR. The mean hepatic activity index and portal inflammation score were higher, the HBV DNA was lower, and the leptin level was similar in children with ETR when compared to others (P = 0.017, P = 0.04, P = 0.007, P = 0.34, respectively). HBV DNA and the fibrosis score were positively correlated (P = 0.016).
Conclusion
: Although the higher leptin value observed in children with ETR was not statistically significant, because of close interactions between leptin, cytokines and lymphocytes, it is thought that leptin should be investigated as a predictive factor of ETR in further studies.