A natural single nucleotide mutation in the small regulatory RNA ArcZ of Dickeya solani switches off the antimicrobial activities against yeast and bacteria

The necrotrophic plant pathogenic bacterium Dickeya solani emerged in the potato agrosystem in Europe. All isolated strains of D. solani contain several large polyketide synthase/non-ribosomal peptide synthetase (PKS/NRPS) gene clusters. Analogy with genes described in other bacteria suggests that the clusters ooc and zms are involved in the production of secondary metabolites of the oocydin and zeamine families, respectively. A third cluster named sol was recently shown to produce an antifungal molecule. In this study, we constructed mutants impaired in each of the three secondary metabolite clusters sol, ooc, and zms to compare first the phenotype of the D. solani wild-type strain D s0432-1 with its associated mutants. We demonstrated the antimicrobial functions of these three PKS/NRPS clusters against bacteria, yeasts or fungi. The cluster sol, conserved in several other Dickeya species, produces a secondary metabolite inhibiting yeasts. Phenotyping and comparative genomics of different D. solani wild-type isolates revealed that the small regulatory RNA ArcZ plays a major role in the control of the clusters sol and zms. A single-point mutation, conserved in some Dickeya wild-type strains, including the D. solani type strain IPO 2222, impairs the ArcZ function by affecting its processing into an active form.

Specificity and genetic polymorphism in the Vfm quorum sensing system of plant pathogenic bacteria of the genus Dickeya

The Vfm quorum sensing (QS) system is preponderant for the virulence of different species of the bacterial genus Dickeya. The vfm gene cluster encodes 26 genes involved in the production, sensing or transduction of the QS signal. To date, the Vfm QS signal has escaped detection by analytical chemistry methods. However, we report here a strain‐specific polymorphism in the biosynthesis genes vfmO and vfmP, which is predicted to be related to the production of different analogues of the QS signal. Consequently, the Vfm communication could be impossible between strains possessing different variants of the genes vfmO/P. We constructed three Vfm QS biosensor strains possessing different vfmO/P variants and compared these biosensors for their responses to samples prepared from 34 Dickeya strains possessing different vfmO/P variants. A pattern of specificity was demonstrated, providing evidence that the polymorphism in the genes vfmO/P determines the biosynthesis of different analogues of the QS signal. Unexpectedly, this vfmO/P‐dependent pattern of specificity is linked to a polymorphism in the ABC transporter gene vfmG, suggesting an adaptation of the putative permease VfmG to specifically bind different analogues of the QS signal. Accordingly, we discuss the possible involvement of VfmG as co‐sensor of the Vfm two‐component regulatory system.

Using Ecology, Physiology, and Genomics to Understand Host Specificity in Xanthomonas

How pathogens coevolve with and adapt to their hosts are critical to understanding how host jumps and/or acquisition of novel traits can lead to new disease emergences. The Xanthomonas genus includes Gram-negative plant-pathogenic bacteria that collectively infect a broad range of crops and wild plant species. However, individual Xanthomonas strains usually cause disease on only a few plant species and are highly adapted to their hosts, making them pertinent models to study host specificity. This review summarizes our current understanding of the molecular basis of host specificity in the Xanthomonas genus, with a particular focus on the ecology, physiology, and pathogenicity of the bacterium. Despite our limited understanding of the basis of host specificity, type III effectors, microbe-associated molecular patterns, lipopolysaccharides, transcriptional regulators, and chemotactic sensors emerge as key determinants for shaping host specificity.

The O-Carbamoyl-Transferase Alb15 Is Responsible for the Modification of Albicidin

Albicidin is a potent antibiotic and phytotoxin produced by Xanthomonas albilineans which targets the plant and bacterial DNA gyrase. We now report on a new albicidin derivative which is carbamoylated at the N-terminal coumaric acid by the action of the ATP-dependent O-carbamoyltransferase Alb15, present in the albicidin (alb) gene cluster. Carbamoyl-albicidin was characterized by tandem mass spectrometry from cultures of a Xanthomonas overproducer strain and the gene function confirmed by gene inactivation of alb15 in X. albilineans. Expression of alb15 in Escherichia coli and in vitro reconstitution of the carbamoyltransferase activity confirmed albicidin as the substrate. The chemical synthesis of carbamoyl-albicidin finally enabled us to assess its bioactivity by means of in vitro gyrase inhibition and antibacterial assays. Compared to albicidin, carbamoyl-albicidin showed a significantly higher inhibitory efficiency against bacterial gyrase (∼8 vs 49 nM), which identifies the carbamoyl group as an important structural feature of albicidin maturation.

Full Genome Sequence Analysis of Two Isolates Reveals a Novel Xanthomonas Species Close to the Sugarcane Pathogen Xanthomonas albilineans

Xanthomonas albilineans is the bacterium responsible for leaf scald, a lethal disease of sugarcane. Within the Xanthomonas genus, X. albilineans exhibits distinctive genomic characteristics including the presence of significant genome erosion, a non-ribosomal peptide synthesis (NRPS) locus involved in albicidin biosynthesis, and a type 3 secretion system (T3SS) of the Salmonella pathogenicity island-1 (SPI-1) family. We sequenced two X. albilineans-like strains isolated from unusual environments, i.e., from dew droplets on sugarcane leaves and from the wild grass Paspalum dilatatum, and compared these genomes sequences with those of two strains of X. albilineans and three of Xanthomonas sacchari. Average nucleotide identity (ANI) and multi-locus sequence analysis (MLSA) showed that both X. albilineans-like strains belong to a new species close to X. albilineans that we have named "Xanthomonas pseudalbilineans". X. albilineans and "X. pseudalbilineans" share many genomic features including (i) the lack of genes encoding a hypersensitive response and pathogenicity type 3 secretion system (Hrp-T3SS), and (ii) genome erosion that probably occurred in a common progenitor of both species. Our comparative analyses also revealed specific genomic features that may help X. albilineans interact with sugarcane, e.g., a PglA endoglucanase, three TonB-dependent transporters and a glycogen metabolism gene cluster. Other specific genomic features found in the "X. pseudalbilineans" genome may contribute to its fitness and specific ecological niche.

The Albicidin Resistance Factor AlbD Is a Serine Endopeptidase That Hydrolyzes Unusual Oligoaromatic-Type Peptides

The para-aminobenzoic acid-containing peptide albicidin is a pathogenicity factor synthesized by Xanthomonas albilineans in infections of sugar cane. Albicidin is a nanomolar inhibitor of the bacterial DNA gyrase with a strong activity against various Gram-negative bacteria. The bacterium Pantoea dispersa expresses the hydrolase AlbD, conferring natural resistance against albicidin. We show that AlbD is a novel type of endopeptidase that catalyzes the cleavage of albicidin at a peptide backbone amide bond, thus abolishing its antimicrobial activity. Additionally, we determined the minimal cleavage motif of AlbD with substrates derived by chemical synthesis. Our results clearly identify AlbD as a unique endopeptidase that is the first member of a new subfamily of peptidases. Our findings provide the molecular basis for a natural detoxification mechanism, potentially rendering a new tool in biological chemistry approaches.

What makes Xanthomonas albilineans unique amongst xanthomonads?

Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. Compared to other species of Xanthomonas, X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy. Its genome, which has experienced significant erosion, has unique genomic features. It lacks two loci required for pathogenicity in other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis and the Hrp-T3SS (hypersensitive response and pathogenicity-type three secretion system) gene clusters. Instead, X. albilineans harbors in its genome an SPI-1 (Salmonella pathogenicity island-1) T3SS gene cluster usually found in animal pathogens. X. albilineans produces a potent DNA gyrase inhibitor called albicidin, which blocks chloroplast differentiation, resulting in the characteristic white foliar stripe symptoms. The antibacterial activity of albicidin also confers on X. albilineans a competitive advantage against rival bacteria during sugarcane colonization. Recent chemical studies have uncovered the unique structure of albicidin and allowed us to partially elucidate its fascinating biosynthesis apparatus, which involves an enigmatic hybrid PKS/NRPS (polyketide synthase/non-ribosomal peptide synthetase) machinery.

The gyrase inhibitor albicidin consists of p-aminobenzoic acids and cyanoalanine

Albicidin is a potent DNA gyrase inhibitor produced by the sugarcane pathogenic bacterium Xanthomonas albilineans. Here we report the elucidation of the hitherto unknown structure of albicidin, revealing a unique polyaromatic oligopeptide mainly composed of p-aminobenzoic acids. In vitro studies provide further insights into the biosynthetic machinery of albicidin. These findings will enable structural investigations on the inhibition mechanism of albicidin and its assessment as a highly effective antibacterial drug.

Total synthesis of albicidin: a lead structure from Xanthomonas albilineans for potent antibacterial gyrase inhibitors

The peptide antibiotic albicidin, which is synthesized by the plant pathogenic bacterium Xanthomonas albilineans, displays remarkable antibacterial activity against various Gram-positive and Gram-negative microorganisms. The low amounts of albicidin obtainable from the producing organism or through heterologous expression are limiting factors in providing sufficient material for bioactivity profiling and structure-activity studies. Therefore, we developed a convergent total synthesis route toward albicidin. The unexpectedly difficult formation of amide bonds between the aromatic amino acids was achieved through a triphosgene-mediated coupling strategy. The herein presented synthesis of albicidin confirms the previously determined chemical structure and underlines the extraordinary antibacterial activity of this compound. The synthetic protocol will provide multigram amounts of albicidin for further profiling of its drug properties.

Fracture incidence after 3 years of aromatase inhibitor therapy

BACKGROUND

The purpose of this study was to describe the fracture incidence and bone mineral density (BMD) evolution in a large cohort of post-menopausal women with breast cancer after 3 years of aromatase inhibitor (AI) therapy.

PATIENTS AND METHODS

A prospective, longitudinal study in real-life setting. Each woman had an extensive medical assessment, a biological evaluation, a BMD measurement, and systematic spinal X-rays at baseline and after 3 years of AI therapy. Women with osteoporosis at baseline (T-score < -2.5 and/or non-traumatic fracture history) were treated by oral weekly bisphosphonates.

RESULTS

Among 497 women (mean age 63.8 ± 9.6 years) included in this study, 389 had a bone evaluation both at baseline and after 3 years of AI therapy: 267 women (mean age 61.2 ± 8.6) with no osteoporosis at baseline and 122 women (mean age 67.2 ± 9.1) with osteoporosis at baseline justifying a weekly oral bisphosphonate treatment. Women without bisphosphonates had a significant decrease in spine BMD (-3.5%, P < 0.01), neck BMD (-2.0%, P < 0.01), and total hip BMD (-2.1%, P < 0.01) over the 3 years but only 15 of them (5.6%) presented an incident vertebral or non-vertebral fracture. In osteoporotic women treated with bisphosphonates, spine and hip BMD were maintained at 3 years but 12 of them (9.8%) had an incident fracture. These fractured women were significantly older (74.1 ± 9.8 versus 66.5 ± 8.8) but also presented BMD loss during treatment suggesting poor adherence to bisphosphonate treatment.

CONCLUSION

This real-life study confirmed that AIs induced moderate bone loss and low fracture incidence in post-menopausal women without initial osteoporosis. In women with baseline osteoporosis and AI therapy, oral bisphosphonates maintain BMD but were associated with a persistent fracture risk, particularly in older women.

Genome sequence of Xanthomonas fuscans subsp. fuscans strain 4834-R reveals that flagellar motility is not a general feature of xanthomonads

BACKGROUND

Xanthomonads are plant-associated bacteria responsible for diseases on economically important crops. Xanthomonas fuscans subsp. fuscans (Xff) is one of the causal agents of common bacterial blight of bean. In this study, the complete genome sequence of strain Xff 4834-R was determined and compared to other Xanthomonas genome sequences.

RESULTS

Comparative genomics analyses revealed core characteristics shared between Xff 4834-R and other xanthomonads including chemotaxis elements, two-component systems, TonB-dependent transporters, secretion systems (from T1SS to T6SS) and multiple effectors. For instance a repertoire of 29 Type 3 Effectors (T3Es) with two Transcription Activator-Like Effectors was predicted. Mobile elements were associated with major modifications in the genome structure and gene content in comparison to other Xanthomonas genomes. Notably, a deletion of 33 kbp affects flagellum biosynthesis in Xff 4834-R. The presence of a complete flagellar cluster was assessed in a collection of more than 300 strains representing different species and pathovars of Xanthomonas. Five percent of the tested strains presented a deletion in the flagellar cluster and were non-motile. Moreover, half of the Xff strains isolated from the same epidemic than 4834-R was non-motile and this ratio was conserved in the strains colonizing the next bean seed generations.

CONCLUSIONS

This work describes the first genome of a Xanthomonas strain pathogenic on bean and reports the existence of non-motile xanthomonads belonging to different species and pathovars. Isolation of such Xff variants from a natural epidemic may suggest that flagellar motility is not a key function for in planta fitness.

Genome mining reveals the genus Xanthomonas to be a promising reservoir for new bioactive non-ribosomally synthesized peptides

BACKGROUND

Various bacteria can use non-ribosomal peptide synthesis (NRPS) to produce peptides or other small molecules. Conserved features within the NRPS machinery allow the type, and sometimes even the structure, of the synthesized polypeptide to be predicted. Thus, bacterial genome mining via in silico analyses of NRPS genes offers an attractive opportunity to uncover new bioactive non-ribosomally synthesized peptides. Xanthomonas is a large genus of Gram-negative bacteria that cause disease in hundreds of plant species. To date, the only known small molecule synthesized by NRPS in this genus is albicidin produced by Xanthomonas albilineans. This study aims to estimate the biosynthetic potential of Xanthomonas spp. by in silico analyses of NRPS genes with unknown function recently identified in the sequenced genomes of X. albilineans and related species of Xanthomonas.

RESULTS

We performed in silico analyses of NRPS genes present in all published genome sequences of Xanthomonas spp., as well as in unpublished draft genome sequences of Xanthomonas oryzae pv. oryzae strain BAI3 and Xanthomonas spp. strain XaS3. These two latter strains, together with X. albilineans strain GPE PC73 and X. oryzae pv. oryzae strains X8-1A and X11-5A, possess novel NRPS gene clusters and share related NRPS-associated genes such as those required for the biosynthesis of non-proteinogenic amino acids or the secretion of peptides. In silico prediction of peptide structures according to NRPS architecture suggests eight different peptides, each specific to its producing strain. Interestingly, these eight peptides cannot be assigned to any known gene cluster or related to known compounds from natural product databases. PCR screening of a collection of 94 plant pathogenic bacteria indicates that these novel NRPS gene clusters are specific to the genus Xanthomonas and are also present in Xanthomonas translucens and X. oryzae pv. oryzicola. Further genome mining revealed other novel NRPS genes specific to X. oryzae pv. oryzicola or Xanthomonas sacchari.

CONCLUSIONS

This study revealed the significant potential of the genus Xanthomonas to produce new non-ribosomally synthesized peptides. Interestingly, this biosynthetic potential seems to be specific to strains of Xanthomonas associated with monocotyledonous plants, suggesting a putative involvement of non-ribosomally synthesized peptides in plant-bacteria interactions.

First Report of Sugarcane Leaf Scald in Gabon Caused by a Highly Virulent and Aggressive Strain of Xanthomonas albilineans

During a disease inspection at the sugarcane estate SUCAF near Franceville, Gabon, in March 2011, 0.5 to 1 cm wide chlorotic stripes covered with many small red streaks were observed on sugarcane (Saccharum spp.) leaves of a single plant of cultivar R581. After removal of the leaves covering the base of the stalks, abnormal development of basal side shoots was also observed. Transversal sections of a diseased stalk showed reddening of the vessels near the nodes. Circular, convex, smooth, shiny, translucent, non-mucoid, honey-yellow pigmented bacterial colonies were isolated from stalk pieces and side shoots on XAS selective agar medium (1). The nucleotide sequence of the 16S-23S internal transcribed spacer (ITS) of a representative colony was shown to be 100% identical to the 16S-23S ITS sequence from the genome of Xanthomonas albilineans strain GPE PC73 (GenBank: FP565176.1). This strain from Gabon was named GAB266. Sugarcane stalks of greenhouse grown cultivar CP68-1026 were inoculated with X. albilineans strains XaFL07-1 from Florida, GPE PC73 from Guadeloupe, and GAB266. Five stalks were inoculated by the modified decapitation method (3) with each strain or with a water control. One month post-inoculation (MPI), white pencil lines and severe necrosis were observed on leaves inoculated with strains XaFL07-1 and GPE PC73, and no disease symptoms appeared on non-inoculated leaves that developed 2 to 3 MPI. These results are in agreement with those generally obtained after inoculation of susceptible sugarcane cultivars with X. albilineans strains from various geographical locations under greenhouse conditions (Rott, unpublished results). In contrast, 1 MPI, only discrete white to red pencil lines were observed along with necrosis on leaves inoculated with strain GAB266, and by 2 to 3 MPI, all five inoculated plants were wilted. The pathogen was successfully reisolated by the stalk blot inoculation technique (3) with XAS medium, from all five inoculated stalks and from 98 of 114 internodes. In a second greenhouse experiment, the same three strains of X. albilineans were inoculated as described above into five sugarcane cultivars differing in resistance to leaf scald in Guadeloupe (2) (CP68-1026, highly susceptible; B69566, susceptible; R570, tolerant; B8008, resistant; Co6415, highly resistant). The same symptoms as those described above were again observed on inoculated leaves of the five sugarcane cultivars 1 MPI. Strains XaFL07-1 and GPE PC73 produced occasionally a single pencil line on non-inoculated leaves 2 to 3 MPI, but only strain GAB266 caused leaf scalding and/or plant death 2 to 3 MPI: cultivar CP68-1026 (5 of 5 plants), B69566 (5 of 5 plants), R570 (4 of 5 plants), B8008 (5 of 5 plants), and only non-inoculated leaves of cultivar Co6415 remained symptomless (5 plants). Strain GAB266 from Gabon appeared, therefore, more virulent and aggressive than the two strains of X. albilineans from Florida and Guadeloupe. To our knowledge, this is the first report of leaf scald of sugarcane in Gabon and the first description of an unusual highly virulent and aggressive strain of X. albilineans. A large-scale survey needs to be undertaken to determine the distribution of leaf scald disease and this new pathotype/race of X. albilineans in Gabon and other geographical locations. References: (1) M. J. Davis et al. Plant Dis. 78:78, 1994. (2) P. Rott et al. Phytopathology 87:1202, 1997 (3) P. Rott et al. Mol. Plant-Microbe Interact. 24:594, 2011.

Genomic insights into strategies used by Xanthomonas albilineans with its reduced artillery to spread within sugarcane xylem vessels

BACKGROUND

Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy compared to other species of Xanthomonas. For example, this species produces a potent DNA gyrase inhibitor called albicidin that is largely responsible for inducing disease symptoms; its habitat is limited to xylem; and the species exhibits large variability. A first manuscript on the complete genome sequence of the highly pathogenic X. albilineans strain GPE PC73 focused exclusively on distinctive genomic features shared with Xylella fastidiosa-another xylem-limited Xanthomonadaceae. The present manuscript on the same genome sequence aims to describe all other pathogenicity-related genomic features of X. albilineans, and to compare, using suppression subtractive hybridization (SSH), genomic features of two strains differing in pathogenicity.

RESULTS

Comparative genomic analyses showed that most of the known pathogenicity factors from other Xanthomonas species are conserved in X. albilineans, with the notable absence of two major determinants of the "artillery" of other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis gene cluster, and the type III secretion system Hrp (hypersensitive response and pathogenicity). Genomic features specific to X. albilineans that may contribute to specific adaptation of this pathogen to sugarcane xylem vessels were also revealed. SSH experiments led to the identification of 20 genes common to three highly pathogenic strains but missing in a less pathogenic strain. These 20 genes, which include four ABC transporter genes, a methyl-accepting chemotaxis protein gene and an oxidoreductase gene, could play a key role in pathogenicity. With the exception of hypothetical proteins revealed by our comparative genomic analyses and SSH experiments, no genes potentially involved in any offensive or counter-defensive mechanism specific to X. albilineans were identified, supposing that X. albilineans has a reduced artillery compared to other pathogenic Xanthomonas species. Particular attention has therefore been given to genomic features specific to X. albilineans making it more capable of evading sugarcane surveillance systems or resisting sugarcane defense systems.

CONCLUSIONS

This study confirms that X. albilineans is a highly distinctive species within the genus Xanthomonas, and opens new perpectives towards a greater understanding of the pathogenicity of this destructive sugarcane pathogen.

Identification of new candidate pathogenicity factors in the xylem-invading pathogen Xanthomonas albilineans by transposon mutagenesis

Xanthomonas albilineans is a xylem-invading pathogen that produces the toxin albicidin that blocks chloroplast differentiation, resulting in disease symptoms of sugarcane leaf scald. In contrast to other xanthomonads, X. albilineans does not possess a hypersensitive response and pathogenicity type III secretion system and does not produce xanthan gum. Albicidin is the only previously known pathogenicity factor in X. albilineans, yet albicidin-deficient mutant strains are still able to efficiently colonize sugarcane. To identify additional host adaptation or pathogenicity factors, sugarcane 'CP80-1743' was inoculated with 1,216 independently derived Tn5 insertions in X. albilineans XaFL07-1 from Florida. Sixty-one Tn5 mutants were affected in development of leaf symptoms or in stalk colonization. The Tn5 insertion sites of these mutants were determined and the interrupted genes were identified using the recently available genomic DNA sequence of X. albilineans GPE PC73 from Guadeloupe. Several pathogenicity-related loci that were not previously reported in Xanthomonas spp. were identified, including loci encoding hypothetical proteins, a membrane fusion protein conferring resistance to novobiocin, transport proteins, TonB-dependent outer-membrane transporters, and an OmpA family outer-membrane protein.

Genomic and evolutionary features of the SPI-1 type III secretion system that is present in Xanthomonas albilineans but is not essential for xylem colonization and symptom development of sugarcane leaf scald

Xanthomonas albilineans is the causal agent of sugarcane leaf scald. Interestingly, this bacterium, which is not known to be insect or animal associated, possesses a type III secretion system (T3SS) belonging to the injectisome family Salmonella pathogenicity island 1 (SPI-1). The T3SS SPI-1 of X. albilineans shares only low similarity with other available T3SS SPI-1 sequences. Screening of a collection of 128 plant-pathogenic bacteria revealed that this T3SS SPI-1 is present in only two species of Xanthomonas: X. albilineans and X. axonopodis pv. phaseoli. Inoculation of sugarcane with knockout mutants showed that this system is not required by X. albilineans to spread within xylem vessels and to cause disease symptoms. This result was confirmed by the absence of this T3SS SPI-1 in an X. albilineans strain isolated from diseased sugarcane. To investigate the importance of the T3SS SPI-1 during the life cycle of X. albilineans, we analyzed T3SS SPI-1 sequences from 11 strains spanning the genetic diversity of this species. No nonsense mutations or frameshifting indels were observed in any of these strains, suggesting that the T3SS SPI-1 system is maintained within the species X. albilineans. Evolutionary features of T3SS SPI-1 based on phylogenetic, recombination, and selection analyses are discussed in the context of the possible functional importance of T3SS SPI-1 in the ecology of X. albilineans.

Low levels of endogenous estradiol protect bone mineral density in young postmenopausal women

OBJECTIVE

Low levels of endogenous estrogens may play a role in the protection of bone mineral density (BMD) in healthy postmenopausal women. The aim of this study was to evaluate the effect of endogenous estradiol and testosterone on bone mass in young and older healthy postmenopausal women.

METHODS

The study involved 99 postmenopausal women aged 55-75 years. The BMDs of the lumbar spine, proximal femur and total skeleton were determined. Measurements were taken of serum calcium, bone alkaline phosphatase, Crosslaps, estradiol, estrone, sex hormone binding globulin, testosterone, bioavailable testosterone and urine calcium. Estradiol was measured using a sensitive assay with a lower detection limit at 5 pg/ml.

RESULTS

A multivariate analysis showed that the BMD of the lumbar spine was significantly predicted by estradiol (p < 0.05), and testosterone (p < 0.0001). Likewise, testosterone was found to be an independent predictor of the BMD of the total femur (p < 0.001) and the total skeleton (p < 0.001). The population was divided into two groups: < or = 65 (Group 1) and > 65 years (Group 2) of age and also stratified according to estradiol levels: > 10 and < or = 10 pg/ml. Significant differences in BMD were found in women in Group 1 in whom estradiol levels higher than 10 pg/ml were associated with a higher BMD of the lumbar spine (+ 14%, p < 0.01), proximal femur (+ 6%, p < 0.05) and total skeleton (+ 7%, p < 0.05) compared with women with estradiol levels below 10 pg/ml. Bone alkaline phosphatase levels (p < 0.05) and serum Crosslaps (not significant) were lower in women in Group 1 with a level of estradiol more than 10 pg/ ml.

CONCLUSION

Endogenous estradiol levels higher than 10 pg/ml and testosterone protected bone mass in healthy postmenopausal women under 65 years of age. These results were not observed in the group of older women.

The complete genome sequence of Xanthomonas albilineans provides new insights into the reductive genome evolution of the xylem-limited Xanthomonadaceae

Background

The Xanthomonadaceae family contains two xylem-limited plant pathogenic bacterial species, Xanthomonas albilineans and Xylella fastidiosa. X. fastidiosa was the first completely sequenced plant pathogen. It is insect-vectored, has a reduced genome and does not possess hrp genes which encode a Type III secretion system found in most plant pathogenic bacteria. X. fastidiosa was excluded from the Xanthomonas group based on phylogenetic analyses with rRNA sequences.

Results

The complete genome of X. albilineans was sequenced and annotated. X. albilineans, which is not known to be insect-vectored, also has a reduced genome and does not possess hrp genes. Phylogenetic analysis using X. albilineans genomic sequences showed that X. fastidiosa belongs to the Xanthomonas group. Order of divergence of the Xanthomonadaceae revealed that X. albilineans and X. fastidiosa experienced a convergent reductive genome evolution during their descent from the progenitor of the Xanthomonas genus. Reductive genome evolutions of the two xylem-limited Xanthomonadaceae were compared in light of their genome characteristics and those of obligate animal symbionts and pathogens.

Conclusion

The two xylem-limited Xanthomonadaceae, during their descent from a common ancestral parent, experienced a convergent reductive genome evolution. Adaptation to the nutrient-poor xylem elements and to the cloistered environmental niche of xylem vessels probably favoured this convergent evolution. However, genome characteristics of X. albilineans differ from those of X. fastidiosa and obligate animal symbionts and pathogens, indicating that a distinctive process was responsible for the reductive genome evolution in this pathogen. The possible role in genome reduction of the unique toxin albicidin, produced by X. albilineans, is discussed.

The US National Cholesterol Education Programme Adult Treatment Panel III (NCEP ATP III): prevalence of the metabolic syndrome in postmenopausal Latin American women

BACKGROUND

Metabolic syndrome (METS) is a strong predictor of cardiovascular risk. Since the prevalence of METS increases after menopause, gynecological routine consultation offers an excellent screening opportunity.

OBJECTIVES

To assess the prevalence of METS in Latin American postmenopausal women and factors modifying its risk; as well as to assess the role of simple routine care measurements in the diagnosis of the METS.

METHODS

A total of 3965 postmenopausal women, aged 45-64 years, seeking health care at 12 gynecological centers in major Latin American cities were included in this cross-sectional study. The US National Cholesterol Education Programme Adult Treatment Panel III (NCEP ATP III) guidelines were applied to assess METS. This was present if three or more of the following conditions were present: waist circumference > or = 88 cm; blood pressure > or = 130/85 mmHg; fasting plasma triglycerides > or = 150 mg/dl; high density lipoprotein (HDL) cholesterol < 50 mg/dl; glucose > or = 110 mg/dl or subjects were receiving treatment for their condition.

RESULTS

The prevalences of having at least two, three, four or five components were 62.5, 35.1, 13.5 and 3.2%, respectively. The prevalence increased from 28.1% in those aged 40-44 years to 42.9% in those aged 60-64 years. The risk of METS detection (multivariate analysis) increased with age (odds ratio (OR) 1.22, 95% confidence interval (CI) 1.03-1.43), time elapsed since menopause (OR 1.18, 95% CI 1.00-1.38), smoking cigarettes (OR 1.40, 95% CI 1.19-1.65), obesity (OR 13.01, 95% CI 10.93-15.49) and hypertension (OR 9.30, 95% CI 7.91-10.94). In contrast, hormone therapy reduces this risk (OR 0.59, 95% CI 0.51-0.70).

CONCLUSION

There is a high prevalence of the metabolic syndrome in postmenopausal Latin American women seeking gynecologic health care. Age, years since menopause, obesity and hypertension are strong predictors of this condition.

Androgens in relationship to cardiovascular risk factors in the menopausal transition

OBJECTIVE

To establish the relationship between androgens and cardiovascular disease (CVD) risk factors in the menopausal transition.

METHODS

A total of 124 women were divided into four groups: 29 premenopausal (PreM), 35 women in the menopausal transition still menstruating (MTM), 29 women in the menopausal transition with 3-6 months amenorrhea (MTA), and 31 postmenopausal women (PostM). Levels of triglycerides, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, glucose and insulin were assayed in all samples and waist circumference was measured. In a subgroup of 83 women (19 PreM, 21 MTM, 28 MTA and 15 PostM), levels of total testosterone, androstenedione, dehydroepiandrosterone sulfate (DHEAS) and estradiol were determined. The free androgen index, Homeostasis Model Assessment (HOMA) index, Quantitative Insulin Sensitivity Check Index (QUICKI) and McAuley index, estradiol/total testosterone and triglyceride/HDL cholesterol ratios were calculated.

RESULTS

Androstenedione was higher in MTA vs. PostM women (p < 0.05); DHEAS was higher in PreM women vs. the other three groups (p < 0.05). Sex hormone binding globulin (SHBG) in MTM women was higher than in MTA women (p < 0.05); the free androgen index was lower in MTM women than in MTA and PostM women. SHBG and the free androgen index showed negative and positive correlations, respectively with waist circumference, insulin resistance and lipids. In a multiple regression analysis, considering waist circumference, neither free androgen index nor SHBG showed significant differences between groups. The waist circumference correlated only with SHBG (p = 0.022) and correlations between SHBG and insulin resistance markers continued to be significant, but relationships between SHBG and lipoproteins and all correlations found with free androgen index were lost.

CONCLUSIONS

An increment in the androgenic milieu that correlates with abdominal fat, insulin resistance and atherogenic lipoproteins becomes evident after the menopausal transition and suggests that evaluation of cardiovascular disease risk in these women should include androgens, considering that abdominal obesity is one of the main determinants of the relationship between androgenic parameters and cardiovascular risk factors.

Increased plasma activity of metalloproteinase 2 in women with metabolic syndrome

Metalloproteinases (MMPs) play a significant role in vascular remodeling, and they have been suspected to be partly responsible for the pathogenesis of cardiovascular disease. Metalloproteinases have been reported to be increased in atherosclerosis and type 2 diabetes mellitus; however, so far they have not been evaluated in metabolic syndrome (MetS). Plasma activity of MMP-2 and MMP-9, high-sensitivity C-reactive protein concentration, dense low-density lipoprotein, and insulin-resistance markers were measured in 38 nondiabetic women with (n = 19) and without (n = 19) MetS. Women with MetS had significantly higher plasma activity of MMP-2 than controls (median [range], 1.3 [0.4-3.1] vs 0.7 [0.1-1.9]; P = .001). MMP-2 activity positively correlated with waist, homeostasis model assessment, and high-sensitivity C-reactive protein (P < .02) as well as with apolipoprotein B, dense low-density lipoprotein, triglycerides/high-density lipoprotein cholesterol index (P < .001) and negatively with high-density lipoprotein cholesterol (P < .002). Our finding of increased plasma activity of MMP-2 in women with MetS is important because they fit in with an early stage of cardiovascular disease; and measurement of soluble molecules may improve the risk assessment, early diagnosis, and prognosis of cardiovascular disease.

Substrate specificity-conferring regions of the nonribosomal peptide synthetase adenylation domains involved in albicidin pathotoxin biosynthesis are highly conserved within the species Xanthomonas albilineans

Albicidin is a pathotoxin produced by Xanthomonas albilineans, a xylem-invading pathogen that causes leaf scald disease of sugarcane. Albicidin is synthesized by a nonribosomal pathway via modular polyketide synthase and nonribosomal peptide synthetase (NRPS) megasynthases, and NRPS adenylation (A) domains are responsible for the recognition and activation of specific amino acid substrates. DNA fragments (0.5 kb) encoding the regions responsible for the substrate specificities of six albicidin NRPS A domains from 16 strains of X. albilineans representing the known diversity of this pathogen were amplified and sequenced. Polymorphism analysis of these DNA fragments at different levels (DNA, protein, and NRPS signature) showed that these pathogenicity loci were highly conserved. The conservation of these loci most likely reflects purifying selective pressure, as revealed by a comparison with the variability of nucleotide and amino acid sequences of two housekeeping genes (atpD and efp) of X. albilineans. Nevertheless, the 16 strains of X. albilineans were differentiated into several groups by a phylogenetic analysis of the nucleotide sequences corresponding to the NRPS A domains. One of these groups was representative of the genetic diversity previously found within the pathogen by random fragment length polymorphism and amplified fragment length polymorphism analyses. This group, which differed by three single synonymous nucleotide mutations, contained only four strains of X. albilineans that were all involved in outbreaks of sugarcane leaf scald. The amount of albicidin produced in vitro in agar and liquid media varied among the 16 strains of X. albilineans. However, no relationship among the amount of albicidin produced in vitro and the pathotypes and genetic diversity of the pathogen was found. The NRPS loci contributing to the synthesis of the primary structure of albicidin apparently are not involved in the observed pathogenicity differences among strains of X. albilineans.

Heterologous production of albicidin: a promising approach to overproducing and characterizing this potent inhibitor of DNA gyrase

The phytotoxin and polyketide antibiotic albicidin produced by Xanthomonas albilineans is a highly potent DNA gyrase inhibitor. Low yields of albicidin production have slowed studies of its chemical structure. Heterologous expression of albicidin biosynthetic genes in X. axonopodis pv. vesicatoria resulted in a sixfold increase in albicidin production, offering promising strategies for engineering overproduction.

Age at menopause in Latin America

OBJECTIVE

To assess the age at menopause (AM) in Latin America urban areas.

DESIGN

A total of 17,150 healthy women, aged 40 to 59 years, accompanying patients to healthcare centers in 47 cities of 15 Latin American countries, were surveyed regarding their age, educational level, healthcare coverage, history of gynecological surgery, smoking habit, presence of menses, and the use of contraception or hormone therapy at menopause. The AM was calculated using logit analysis.

RESULTS

The mean age of the entire sample was 49.4 +/- 5.5 years. Mean educational level was 9.9 +/- 4.5 years, and the use of hormone therapy and oral contraception was 22.1% and 7.9%, respectively. The median AM of women in all centers was 48.6 years, ranging from 43.8 years in Asuncion (Paraguay) to 53 years in Cartagena de Indias (Colombia). Logistic regression analysis determined that women aged 49 living in cities at 2,000 meters or more above sea level (OR = 2.0, 95% CI: 1.4-2.9, P < 0.001) and those with lower educational level (OR = 1.9, 95% CI: 1.3-2.8, P < 0.001) or living in countries with low gross national product (OR = 2.1, 95% CI: 1.5-2.9, P < 0.001) were more prone to an earlier onset of menopause.

CONCLUSIONS

The AM varies widely in Latin America. Lower income and related poverty conditions influence the onset of menopause.

High Variation in Pathogenicity of Genetically Closely Related Strains of Xanthomonas albilineans, the Sugarcane Leaf Scald Pathogen, in Guadeloupe

ABSTRACT Pathogenicity of 75 strains of Xanthomonas albilineans from Guadeloupe was assessed by inoculation of sugarcane cv. B69566, which is susceptible to leaf scald, and 19 of the strains were selected as representative of the variation in pathogenicity observed based on stalk colonization. In vitro production of albicidin varied among these 19 strains, but the restriction fragment length polymorphism pattern of their albicidin biosynthesis genes was identical. Similarly, no genomic variation was found among strains by pulsed-field gel electrophoresis. Some variation among strains was found by amplified fragment length polymorphism, but no relationship between this genetic variation and variation in pathogenicity was found. Only 3 (pilB, rpfA, and xpsE) of 40 genes involved in pathogenicity of bacterial species closely related to X. albilineans could be amplified by polymerase chain reaction from total genomic DNA of all nine strains tested of X. albilineans differing in pathogenicity in Guadeloupe. Nucleotide sequences of these genes were 100% identical among strains, and a phylogenetic study with these genes and housekeeping genes efp and ihfA suggested that X. albilineans is on an evolutionary road between the X. campestris group and Xylella fastidiosa, another vascular plant pathogen. Sequencing of the complete genome of Xanthomonas albilineans could be the next step in deciphering molecular mechanisms involved in pathogenicity of X. albilineans.

Efficient production of Agrobacterium rhizogenes-transformed roots and composite plants for studying gene expression in coffee roots

The possibility of rapid validation and functional analysis of nematode resistance genes is a common objective for numerous species and particularly for woody species. In this aim, we developed an Agrobacterium rhizogenes-mediated transformation protocol for Coffea arabica enabling efficient and rapid regeneration of transformed roots from the hypocotyls of germinated zygotic embryos, and the subsequent production of composite plants. The A. rhizogenes strain A4RS proved to be the most virulent. High transformation efficiencies (70%) were obtained using a 2-week co-cultivation period at a temperature of 15-18 degrees C. Using a p35S-gusA-int construct inserted in the pBIN19 binary plasmid, we could estimate that 35% of transformed roots were GUS positive (co-transformed). Using the GUS assay as visual marker, 40% composite plants bearing a branched co-transformed rootstock could be obtained after only 12 weeks without selection with herbicides or antibiotics. Transgenic coffee roots obtained with A. rhizogenes did not exhibit the 'hairy' disturbed phenotype and were morphologically similar to normal roots. PCR analyses demonstrated that all co-transformed roots were positive for the expected rolB and gusA genes. Transformed and non-transformed root systems from both susceptible and resistant varieties were inoculated with Meloidogyne exigua nematode individuals. Inoculation of composite plants from the Caturra susceptible variety resulted in the normal development of nematode larvae. Numbers of extracted nematodes demonstrated that transformed roots retain the resistance/sensibility phenotype of varieties from which they are derived. These results suggest that composite plants constitute a powerful tool for studying nematode resistance genes.

Geographical Distribution of Four Sugarcane yellow leaf virus Genotypes

Specific primer pairs were designed to distinguish four genotypes (BRA for Brazil, CUB for Cuba, PER for Peru, and REU for Réunion Island) of Sugarcane yellow leaf virus (SCYLV) by reverse transcription-polymerase chain reaction (RT-PCR). A unique genome fragment was amplified from each genotype, with the exception of genotypes BRA and PER that are phylogenetically relatively close and were designated genotype BRA-PER. These RT-PCR primers were then used to identify the SCYLV genotype(s) present in 18 different sugarcane growing locations in the world, and 245 leaf samples infected by the virus were analyzed. Most samples were infected by only one of the three genotypes, but mixed infections occurred. Genotype BRA-PER was found in all sugarcane growing locations, whereas genotypes CUB and REU were each found in four geographical locations only. Genotypes BRA-PER, CUB, and REU were all three detected in locally bred sugarcane cultivars in Guadeloupe, indicating local transmission of these genotypes. In contrast, only genotypes BRA-PER and CUB were found in locally bred cultivars in Brazil, whereas genotype REU was detected in this country in cultivar R570 imported from Réunion. Similarly, genotypes BRA-PER and REU are both present in Réunion, but genotype BRA-PER has not, as of yet, spread on this island. Presence of several SCYLV genotypes in Brazil, Colombia, Guadeloupe, Mauritius, and Réunion suggests different virus introductions and/or different evolution histories of the virus after its introduction into a new environment.

Metabolic syndrome throughout the menopausal transition: influence of age and menopausal status

OBJECTIVE

To assess the relationship between the main components of both the metabolic syndrome and insulin resistance and menopausal status in the menopausal transition.

METHODS

A total of 124 healthy women were divided into four groups according to their menstrual status: the first group consisted of 35 women in menopausal transition with menstrual bleeding (MTM) and with cycles between 35 and 80 days; the second group was composed of 29 women in menopausal transition with 3-6 months of amenorrhea (MTA). The third group consisted of 31 postmenopausal women (PostM) and the fourth group of 29 premenopausal women (PreM) with regular cycles. The metabolic syndrome was evaluated following the ATP III criteria. Evaluation of insulin resistance was made through the HOMA, QUICKI and McAuley indices and the triglycerides/high density lipoprotein (HDL) cholesterol ratio.

RESULTS

The triglycerides/HDL cholesterol ratio increased in MTM, MTA and PostM women in comparison with PreM women. A slight decrease in the QUIKI index (p = 0.06) and a decrease in the McAuley index (p < 0.001) were observed in MTM, MTA and PostM women in comparison to PreM women. The relative frequencies of metabolic syndrome in the four groups were: PreM, 0%; MTM, 20%; MTA, 21%; and PostM, 22% (p = 0.0001). The most frequent markers of the metabolic syndrome were increased waist circumference, low HDL cholesterol levels and hypertension. Linear regression between menopausal status and metabolic syndrome was lost when age was added to the model.

CONCLUSIONS

The frequency of metabolic syndrome increased from the time of the menopausal transition to the postmenopause. Abdominal obesity was the most frequent feature observed. Nevertheless, aging erased the effect of the menopause on the metabolic syndrome. In order to prevent cardiovascular disease, the metabolic syndrome must be evaluated from the time of the menopausal transition.

Xanthomonas albilineans HtpG is required for biosynthesis of the antibiotic and phytotoxin albicidin

Xanthomonas albilineans, the causal agent of leaf scald disease of sugarcane, produces a highly potent polyketide-peptide antibiotic and phytotoxin called albicidin. Previous studies established the involvement of a large cluster of genes in the biosynthesis of this toxin. We report here the sub-cloning and sequencing of an additional gene outside of the main cluster and essential for albicidin biosynthesis. This gene encodes a 634-amino-acid protein that shows high identity with the Escherichia coli heat shock protein HtpG. Complementation studies of X. albilineans Tox- mutants confirmed the requirement of htpG for albicidin biosynthesis and revealed functional interchangeability between E. coli and X. albilineans htpG genes. HtpG was co-localised with albicidin in the cellular membrane, i.e., the cellular fraction where the toxin is most probably biosynthesised. Here we show the requirement of an HtpG protein for the biosynthesis of a polyketide-peptide antibiotic.

Yellow leaf of sugarcane is caused by at least three different genotypes of sugarcane yellow leaf virus, one of which predominates on the Island of Réunion

The genetic diversity of sugarcane yellow leaf virus (SCYLV) was analyzed with 43 virus isolates from Réunion Island and 17 isolates from world-wide locations. We attempted to amplify by reverse-transcription polymerase chain reaction (RT-PCR), clone, and sequence four different fragments covering 72% of the genome of these virus isolates. The number of amplified isolates and useful sequence information varied according to each fragment, whereas an amplicon was obtained with diagnostic primers for 59 out of 60 isolates (98%). Phylogenetic analyses of the sequences determined here and additional sequences of 11 other SCYLV isolates available from GenBank showed that SCYLV isolates were distributed in different phylogenetic groups or belonged to single genotypes. The majority of isolates from Réunion Island were grouped in phylogenetic clusters that did not contain any isolates from other origins. The complete six ORFs (5612 bp) of five SCYLV isolates (two from Réunion Island, one from Brazil, one from China, and one from Peru) were amplified, cloned, and sequenced. The existence of at least three distinct genotypes of SCYLV was shown by phylogenetic analysis of the sequences of these isolates and additional published sequences of three SCYLV isolates (GenBank accessions). The biological significance of these genotypes and of the origin of the distinct lineage of SCYLV in Réunion Island remains to be determined.