Chromogranin-A Expression in Neoplastic Neuroendocrine Cells and Prognosis in Colorectal Cancer

Aims

Chromogranin-A (CG), a cytoplasmic glycoprotein, is one of the markers most frequently used to identify the presence of neuroendocrine cells in the human gastrointestinal tract. Several authors have identified a subgroup of colorectal cancer patients with a severe prognosis whose tumors contained neuroendocrine CG-positive cells. In the present study, CG expression in 100 patients with colorectal adenocarcinoma treated from January 1983 to December 1988 with potentially curative surgery was analyzed and correlated with other prognostic factors and 5-year survival rate.

Methods

Samples tested immunohistochemically for CG were divided into three groups: I) negative; II) less than 1 CG-positive cell/mm2; III) more than 1 CG-positive cell/mm2.

Results

Of 100 patients with primary colorectal adenocarcinoma, 79% had tumors comprised of CG-negative cells, 17% had rare CG-positive cells, and 4% of cases could be classified in group III. No significant relation between CG expression and location of primary tumor, bowel wall infiltration, stage of disease or tumor grade according to Broders and Jass was observed. The 5-year survival was 53% and 52% for CG-positive and CG-negative lesions, respectively. Survival of patients with Dukes-Kirklin stage C and D was comparable in patients with CG-positive (33.3%) and CG-negative (30%) tumors.

Conclusions

CG expression cannot, at present, be recommended as a marker to identify prognostic subgroups in colorectal cancer patients.

Intraradical colonization by arbuscular mycorrhizal fungi triggers induction of a lipochitooligosaccharide receptor

Functional divergence of paralogs following gene duplication is one of the mechanisms leading to evolution of novel pathways and traits. Here we show that divergence of Lys11 and Nfr5 LysM receptor kinase paralogs of Lotus japonicus has affected their specificity for lipochitooligosaccharides (LCOs) decorations, while the innate capacity to recognize and induce a downstream signalling after perception of rhizobial LCOs (Nod factors) was maintained. Regardless of this conserved ability, Lys11 was found neither expressed, nor essential during nitrogen-fixing symbiosis, providing an explanation for the determinant role of Nfr5 gene during Lotus-rhizobia interaction. Lys11 was expressed in root cortex cells associated with intraradical colonizing arbuscular mycorrhizal fungi. Detailed analyses of lys11 single and nfr1nfr5lys11 triple mutants revealed a functional arbuscular mycorrhizal symbiosis, indicating that Lys11 alone, or its possible shared function with the Nod factor receptors is not essential for the presymbiotic phases of AM symbiosis. Hence, both subfunctionalization and specialization appear to have shaped the function of these paralogs where Lys11 acts as an AM-inducible gene, possibly to fine-tune later stages of this interaction.

Defense related phytohormones regulation in arbuscular mycorrhizal symbioses depends on the partner genotypes

Arbuscular mycorrhizal (AM) symbioses are mutualistic associations between soil fungi and most vascular plants. Modulation of the hormonal and transcriptional profiles, including changes related to defense signalling, has been reported in many host plants during AM symbioses. These changes have been often related to the improved stress tolerance common in mycorrhizal plants. However, results on the alterations in phytohormones content and their role on the symbiosis are controversial. Here, an integrative analysis of the response of phylogenetically diverse plants (i.e., tomato, soybean, and maize) to two mycorrhizal fungi -Funneliformis mosseae and Rhizophagus irregularis- was performed. The analysis of the defense-related hormones salicylic acid, abscisic acid, and jasmonates, and the expression of marker genes of the pathways they regulate, revealed significant changes in the roots of mycorrhizal plants. These changes depended on both the plant and the AM fungus (AMF) involved. However, general trends can be identified: roots associated with the most effective colonizer R. irregularis showed fewer changes in these defense-related traits, while the colonization by F. mosseae led to significant modifications in all plants tested. The up-regulation of the jasmonate pathway by F. mosseae was found to be highly conserved among the different plant species, suggesting an important role of jasmonates during this AM interaction. Our study evidences a strong influence of the AMF genotype on the modulation of host defense signalling, and offers hints on the role of these changes in the symbiosis.

The transcriptome of the arbuscular mycorrhizal fungus Glomus intraradices (DAOM 197198) reveals functional tradeoffs in an obligate symbiont

• The arbuscular mycorrhizal symbiosis is arguably the most ecologically important eukaryotic symbiosis, yet it is poorly understood at the molecular level. To provide novel insights into the molecular basis of symbiosis-associated traits, we report the first genome-wide analysis of the transcriptome from Glomus intraradices DAOM 197198. • We generated a set of 25,906 nonredundant virtual transcripts (NRVTs) transcribed in germinated spores, extraradical mycelium and symbiotic roots using Sanger and 454 sequencing. NRVTs were used to construct an oligoarray for investigating gene expression. • We identified transcripts coding for the meiotic recombination machinery, as well as meiosis-specific proteins, suggesting that the lack of a known sexual cycle in G. intraradices is not a result of major deletions of genes essential for sexual reproduction and meiosis. Induced expression of genes encoding membrane transporters and small secreted proteins in intraradical mycelium, together with the lack of expression of hydrolytic enzymes acting on plant cell wall polysaccharides, are all features of G. intraradices that are shared with ectomycorrhizal symbionts and obligate biotrophic pathogens. • Our results illuminate the genetic basis of symbiosis-related traits of the most ancient lineage of plant biotrophs, advancing future research on these agriculturally and ecologically important symbionts.

Multiple exocytotic markers accumulate at the sites of perifungal membrane biogenesis in arbuscular mycorrhizas

Arbuscular mycorrhizas (AMs) are symbiotic interactions established within the roots of most plants by soil fungi belonging to the Glomeromycota. The extensive accommodation of the fungus in the root tissues largely takes place intracellularly, within a specialized interface compartment surrounded by the so-called perifungal membrane, an extension of the host plasmalemma. By combining live confocal imaging of green fluorescent protein (GFP)-tagged proteins and transmission electron microscopy (TEM), we have investigated the mechanisms leading to the biogenesis of this membrane. Our results show that pre-penetration responses and symbiotic interface construction are associated with extensive membrane dynamics. They involve the main components of the exocytotic machinery, with a major participation of the Golgi apparatus, as revealed by both TEM and in vivo GFP imaging. The labeling of known exocytosis markers, such as v-SNARE proteins of the VAMP72 family and the EXO84b subunit of the exocyst complex, allowed live imaging of the cell components involved in perifungal membrane construction, clarifying how this takes place ahead of the growing intracellular hypha. Lastly, our novel data are used to illustrate a model of membrane dynamics within the pre-penetration apparatus during AM fungal penetration.

Multiple exocytotic markers accumulate at the sites of perifungal membrane biogenesis in arbuscular mycorrhizas

Arbuscular mycorrhizas (AMs) are symbiotic interactions established within the roots of most plants by soil fungi belonging to the Glomeromycota. The extensive accommodation of the fungus in the root tissues largely takes place intracellularly, within a specialized interface compartment surrounded by the so-called perifungal membrane, an extension of the host plasmalemma. By combining live confocal imaging of green fluorescent protein (GFP)-tagged proteins and transmission electron microscopy (TEM), we have investigated the mechanisms leading to the biogenesis of this membrane. Our results show that pre-penetration responses and symbiotic interface construction are associated with extensive membrane dynamics. They involve the main components of the exocytotic machinery, with a major participation of the Golgi apparatus, as revealed by both TEM and in vivo GFP imaging. The labeling of known exocytosis markers, such as v-SNARE proteins of the VAMP72 family and the EXO84b subunit of the exocyst complex, allowed live imaging of the cell components involved in perifungal membrane construction, clarifying how this takes place ahead of the growing intracellular hypha. Lastly, our novel data are used to illustrate a model of membrane dynamics within the pre-penetration apparatus during AM fungal penetration.

Laparoscopic appendectomy for complicated acute appendicitis

The role of laparoscopic appendectomy in complicated appendicitis is still not widely accepted. The authors report their retrospective study performed to evaluate the effectiveness of the laparoscopic approach in the management of complicated appendicitis. From January 2003 to October 2008, 552 patients underwent appendectomy in our surgical department. Among these, 358 were not complicated appendicitis while 194 were complicated. Of the 194 cases of complicated appendicitis, 121 patients underwent laparoscopic appendectomy while the remaining 73 cases were treated by conventional open surgery. The average length of hospital stay was 5.7 days, with a range from 4 to 13 days. Post-operative complications were observed in a total 11 patients (9.1%), including 3 cases of intra abdominal abscess (2.5%), 2 cases of umbilical wound infection (1.6%) and 6 cases of prolonged ileus (4.9%). Our experience suggests that the laparoscopic procedure is a valid, safe and feasible option to manage acute complicated appendicitis.

[Primary duodenal adenocarcinoma: report of three cases, prognostic factors and therapeutic approach]

Three cases of histologically proven primary non-ampullary adenocarcinoma of the duodenum, observed in our Department from 2001 to 2004, are described. The cases were treated by pancreaticoduodenectomy, duodenal resection and transduodenal excision, respectively. The rarity of this pathology is documented by few retrospective studies and justifies discussion about the main prognostic factors and the best therapeutic approach. We analyze diagnostic, therapeutic and prognostic factors after a revision of literature.

The impact of tillage practices on arbuscular mycorrhizal fungal diversity in subtropical crops

Arbuscular mycorrhizal fungi (AMF) are a main component of soil microbiota in most agrosystems. As obligately mutualistic symbionts, they colonize the roots of the majority of plants, including crop plants. We used molecular techniques to investigate how different tillage systems (moldboard, shred-bedding, subsoil-bedding, and no tillage) can influence the AM fungal community colonizing maize, bean, and sorghum roots in an experimental site located in northern Tamaulipas, Mexico. Roots from 36 plants were analyzed using AM fungal-specific primers to partially amplify the small subunit (SSU) of the ribosomal DNA genes. More than 880 clones were screened for restriction fragment length polymorphism (RFLP) variation, and 173 of these were sequenced. Ten AM fungal types were identified and clustered into three AM fungal families: Gigasporaceae, Glomaceae, and Paraglomaceae. Glomus was the dominating taxon in all the samples. Four of the 10 identified types were distinct from any previously published sequences and could correspond to either known unsequenced species or unknown species. The fungal diversity was low in the four agriculture management systems, but the multidimensional scaling (MDS) analysis and log-linear-saturated model indicated that the composition of the AMF community was significantly affected by the tillage system. In conclusion, since some fungal types were treatment specific, agricultural practices could directly or indirectly influence AM biodiversity.

[Covered perforation of solitary cecal diverticulum: case report]

Acute right lower abdominal pain is often clinically difficult to diagnose. The diagnosis, especially in young patients, is frequently oriented to appendicular disease. Surgical exploration only confirms diagnosis or surprises the surgeon, revealing an unexpected right colon diverticulitis. This emergency condition challenges the surgeon with the dilemma about the best therapeutic choice: conservative or radical treatment? The elective localization of diverticulitis to the right colon is very rare (6.6-14%). The authors report a case of covered perforation of a solitary cecal diverticulum.

[Surgical timing in bleeding liver adenoma: case report]

The diagnosis of liver adenoma, which etiopathogenesis most often involves a prolonged assumption of estrogen (90% of adenomas occurs in women after more than 5 years of estrogen therapy), always imposes a surgical resection. The reason depend from neoplasia characteristics like the malignant evolution (4%) and the high risk of abdominal/intratumoral bleeding (30-50%), that increases during pregnancy and postpartum period. Regression of lesion after discontinuation of hormone therapy is rare and does not remove the degeneration and/or haemorrhagic risk. Liver resection should be performed with appropriate selective endovascular embolization, considering that an inept emergency surgery may impose a greater risk ot the liver, exposing the patient to major risk of morbidity and mortality. The correct timing from embolization to elective surgery is not yet standardized in the literature. The surgeon's personal experience and mainly a careful patient follow-up suggest the timing of surgery after embolization. The authors relate their own experience about the therapeutic strategy and surgical timing in a case of bleeding liver adenoma.

Expression profiles of a phosphate transporter gene (GmosPT) from the endomycorrhizal fungus Glomus mosseae

Arbuscular mycorrhizal (AM) fungi have long been shown to successfully contribute to phosphate uptake by plant roots. The first step of the fungus-mediated uptake is carried out by fungal membrane Pi transporters (PT) that transfer Pi from the soil into the extraradical hyphae. In the present work we report the identification and characterisation of a PT gene from Glomus mosseae, an AM fungus important for natural and agricultural ecosystems. Degenerate primers and rapid amplification of cDNA ends-polymerase chain reaction (PCR) allowed us to obtain a sequence (GmosPT) showing a highly significant similarity with GiPT and GvPT, the only two other PT genes already isolated from AM fungi. Reverse transcriptase-PCR experiments were carried out to study GmosPT expression profiles in structures corresponding to different fungal life stages (quiescent and germinated sporocarps, intraradical and extraradical hyphae) and in extra- and intraradical hyphae exposed to high and low Pi concentrations. GmosPT showed an expression pattern similar to GiPT, the Glomus intraradices PT gene, since its transcript was more abundant in the extraradical mycelium treated with micromolar Pi levels. In addition, the intraradical mycelium also showed a significant GmosPT expression level that was independent from external Pi concentrations. This finding opens new questions about the role and functioning of high-affinity PT in AM fungi.

Differential location of alpha-expansin proteins during the accommodation of root cells to an arbuscular mycorrhizal fungus

alpha-Expansins are extracellular proteins that increase plant cell-wall extensibility. We analysed their pattern of expression in cucumber roots in the presence and in the absence of the mycorrhizal fungus, Glomus versiforme. The distribution of alpha-expansins was investigated by use of two polyclonal antibodies (anti-EXPA1 and anti-EXPA2, prepared against two different cucumber alpha-expansins) in immunoblotting, immunofluorescence, and immunogold experiments. Immunoblot results indicate the presence of a 30-kDa band specific for mycorrhizal roots. The two antibodies identify antigens with a different distribution in mycorrhizal roots: anti-EXPA1 labels the interface zone, but the plant cell walls only weakly. By contrast, the anti-EXPA2 labels only the plant cell walls. In order to understand the potential role of alpha-expansins during the accommodation of the fungus inside root cells, we prepared semi-thin sections to measure the size of cortical cells and the thickness of cortical cell walls in mycorrhizal and non-mycorrhizal root. Mycorrhizal cortical cells were significantly larger than non-mycorrhizal cells and had thicker cell walls. In double-labelling experiments with cellobiohydrolase-gold complex, we observed that cellulose was co-localized with alpha-expansins. Taken together, the results demonstrate that alpha-expansins are more abundant in the cucumber cell walls upon mycorrhizal infection; we propose that these wall-loosening proteins are directly involved in the accommodation of the fungus by infected cortical cells.

Differential location of alpha-expansin proteins during the accommodation of root cells to an arbuscular mycorrhizal fungus

alpha-Expansins are extracellular proteins that increase plant cell-wall extensibility. We analysed their pattern of expression in cucumber roots in the presence and in the absence of the mycorrhizal fungus, Glomus versiforme. The distribution of alpha-expansins was investigated by use of two polyclonal antibodies (anti-EXPA1 and anti-EXPA2, prepared against two different cucumber alpha-expansins) in immunoblotting, immunofluorescence, and immunogold experiments. Immunoblot results indicate the presence of a 30-kDa band specific for mycorrhizal roots. The two antibodies identify antigens with a different distribution in mycorrhizal roots: anti-EXPA1 labels the interface zone, but the plant cell walls only weakly. By contrast, the anti-EXPA2 labels only the plant cell walls. In order to understand the potential role of alpha-expansins during the accommodation of the fungus inside root cells, we prepared semi-thin sections to measure the size of cortical cells and the thickness of cortical cell walls in mycorrhizal and non-mycorrhizal root. Mycorrhizal cortical cells were significantly larger than non-mycorrhizal cells and had thicker cell walls. In double-labelling experiments with cellobiohydrolase-gold complex, we observed that cellulose was co-localized with alpha-expansins. Taken together, the results demonstrate that alpha-expansins are more abundant in the cucumber cell walls upon mycorrhizal infection; we propose that these wall-loosening proteins are directly involved in the accommodation of the fungus by infected cortical cells.

Isolation, free-living capacities, and genome structure of "Candidatus Glomeribacter gigasporarum," the endocellular bacterium of the mycorrhizal fungus Gigaspora margarita

"Candidatus Glomeribacter gigasporarum" is an endocellular beta-proteobacterium present in the arbuscular mycorrhizal (AM) fungus Gigaspora margarita. We established a protocol to isolate "Ca. Glomeribacter gigasporarum" from its host which allowed us to carry out morphological, physiological, and genomic investigations on purified bacteria. They are rod shaped, with a cell wall typical of gram-negative bacteria and a cytoplasm rich in ribosomes, and they present no flagella or pili. Isolated bacteria could not be grown in any of the 19 culture media tested, but they could be kept alive for up to 4 weeks. PCR-based investigations of purified DNA from isolated bacteria did not confirm the presence of all genes previously assigned to "Ca. Glomeribacter gigasporarum." In particular, the presence of nif genes could not be detected. Pulsed-field gel electrophoresis analyses allowed us to estimate the genome size of "Ca. Glomeribacter gigasporarum" to approximately 1.4 Mb with a ca. 750-kb chromosome and a 600- to 650-kb plasmid. This is the smallest genome known for a beta-proteobacterium. Such small genome sizes are typically found in endocellular bacteria living permanently in their host. Altogether, our data suggest that "Ca. Glomeribacter gigasporarum" is an ancient obligate endocellular bacterium of the AM fungus G. margarita.

Vertical transmission of endobacteria in the arbuscular mycorrhizal fungus Gigaspora margarita through generation of vegetative spores

Arbuscular mycorrhizal (AM) fungi living in symbiotic association with the roots of vascular plants have also been shown to host endocellular rod-shaped bacteria. Based on their ribosomal sequences, these endobacteria have recently been identified as a new taxon, Candidatus Glomeribacter gigasporarum. In order to investigate the cytoplasmic stability of the endobacteria in their fungal host and their transmission during AM fungal reproduction (asexual), a system based on transformed carrot roots and single-spore inocula of Gigaspora margarita was used. Under these in vitro sterile conditions, with no risk of horizontal contamination, the propagation of endobacteria could be monitored, and it was shown, by using primers designed for both 16S and 23S ribosomal DNAs, to occur through several vegetative spore generations (SG0 to SG4). A method of confocal microscopy for quantifying the density of endobacteria in spore cytoplasm was designed and applied; endobacteria were consistently found in all of the spore generations, although their number rapidly decreased from SG0 to SG4. The study demonstrates that a vertical transmission of endobacteria takes place through the fungal vegetative generations (sporulation) of an AM fungus, indicating that active bacterial proliferation occurs in the coenocytic mycelium of the fungus, and suggests that these bacteria are obligate endocellular components of their AM fungal host.

Chlorophyllous and achlorophyllous specimens of Epipactis microphylla,(Neottieae, Orchidaceae) are associated with ectomycorrhizal septomycetes, including truffles

Mycoheterotrophic species (i.e., achlorophyllous plants obtaining carbon from their mycorrhizal fungi) arose many times in evolution of the Neottieae, an orchid tribe growing in forests. Moreover, chlorophyllous Neottieae species show naturally occurring achlorophyllous individuals. We investigated the fungal associates of such a member of the Neottieae, Epipactis microphylla, to understand whether their mycorrhizal fungi predispose the Neottieae to mycoheterotrophy. Root symbionts were identified by sequencing the fungal ITS of 18 individuals from three orchid populations, including achlorophyllous and young, subterranean individuals. No rhizoctonias (the usual orchid symbionts) were recovered, but 78% of investigated root pieces were colonized by Tuber spp. Other Pezizales and some Basidiomycetes were also found. Using electron microscopy, we demonstrated for the first time that ascomycetes, especially truffles, form typical orchid mycorrhizae. All identified fungi (but one) belonged to taxa forming ectomycorrhizae on tree roots, and four of them were even shown to colonize surrounding trees. This is reminiscent of mycoheterotrophic orchid species that also associate with ectomycorrhizal fungi, although with higher specificity. Subterranean and achlorophyllous E. microphylla individuals thus likely rely on tree photosynthates, and a partial mycoheterotrophy in individuals plants can be predicted. We hypothesize that replacement of rhizoctonias by ectomycorrhizal symbionts in Neottieae entails a predisposition to achlorophylly.

Zinc ions alter morphology and chitin deposition in an ericoid fungus

A sterile mycelium PS IV, an ascomycete capable of establishing ericoid mycorrhizas, was used to investigate how zinc ions affect the cellular mechanisms of fungal growth. A significant reduction of the fungal biomass was observed in the presence of millimolar zinc concentrations; this mirrored conspicuous changes in hyphal morphology which led to apical swellings and increased branching in the subapical parts. Specific probes for fluorescence and electron microscopy localised chitin, the main cell wall polysaccharide, on the inner part of the fungal wall and on septa in control specimens. In Zn-treated mycelium, hyphal walls were thicker and a more intense chitin labelling was detected on the transverse walls. A quantitative assay showed a significant increase in the amount of chitin in metal-treated hyphae.

Plants, mycorrhizal fungi and endobacteria: a dialog among cells and genomes

This review focuses on mycorrhizas, which are associations between fungi and the roots of 90% of terrestrial plants. These are the most common symbioses in the world; they involve about 6000 species of fungi distributed through all the fungal phyla and about 240000 species of plants, including forest and crop plants. Thanks to mycorrhizal symbiosis and nutrient exchanges, regulated by complex molecular signals, the plant improves its vegetative growth, while the fungus accomplishes its life cycle. Molecular and cellular analyses demonstrate that during colonization the cellular organization of the two eukaryotes is completely remodeled. For example, in cortical cells, structural modifications involve both the host and the microbiont. Recent studies revealed that in arbuscular mycorrhizas (AM), system complexity is increased by the presence of a third symbiont: a bacterium living inside the fungus. The presence of this resident genome makes the investigation of the molecular dialogues among the symbiotic partners even more complex. Molecular analysis showed that the bacterium has genes involved in the acquisition of mineral nutrients. The experimental data support the current view that mycorrhizal symbioses are often tripartite associations.

Two genetically related strains of Tuber borchii produce Tilia mycorrhizas with different morphological traits

Two genetically related strains of Tuber borchii Vittad. (1BO and 43BO) produce mycorrhizas with Tilia platyphyllos Scop. with a different degree of efficiency. The aim of this work was to characterize the morphology of the fungal symbiotic structures in order to examine potential relationships between the anatomical traits of the mycorrhiza, the mycorrhizal capacities of the fungal strains and their effect on the host plants. Some morphological features of mantle hyphae (small size, intense staining, vacuolization, abundance of mitochondria) led to a mantle with morphological features that were isolate-specific. There were unexpected differences, at least under our experimental conditions: 1BO strain mantle cells were larger, less reactive to staining, more highly vacuolated and poorer in mitochondria than those of 43BO. These features were found throughout the mantle in 1BO, while the inner mantle hyphae of 43BO were significantly smaller and more intensely stained than the outer cells. In the 43BO strain there was a positive relation between these features and higher infectivity (evaluated as percentage of mycorrhizal tips) as well as a slightly more effective stimulation of plant growth. These observations suggest that genetically related truffle strains produce mycorrhizas with different morphologies, which may be related to a more efficient response of the host plant to inoculation.

Hydrophobins in ectomycorrhizas: heterologous transcription of the Pisolithus HydPt-1 gene in yeast and Hebeloma cylindrosporum

Hydrophobins are fungal cell wall proteins involved in aggregation of hyphae. Upon the development of the ectomycorrhizal symbiosis between tree roots and fungal hyphae, the transcripts of hydrophobin genes markedly accumulated. As the precise role of these proteins in symbiosis is not yet known, we develop heterologous expression system of the Pisolithus hydrophobin HYDPt-1. This gene has been introduced in Saccharomyces cerevisiae and in the ectomycorrhizal basidiomycete Hebeloma cylindrosporum. Introns were required for hydPt-1 transcript accumulation in the basidiomycete H. cylindrosporum. Heterologous transcript accumulation did not alter the phenotype of either species. The lack of altered phenotype resulted from the absence of HYDPt-1 polypeptide accumulation in transformed strains.

Epidermal cells of a symbiosis-defective mutant of Lotus japonicus show altered cytoskeleton organisation in the presence of a mycorrhizal fungus

The influence of the mycorrhizal fungus Gigaspora margarita on cytoskeleton organisation in epidermal cells of Lotus japonicus roots was compared between plants of the wild type Gifu and the mutant Ljsym4-2, in which the fungus is confined to the epidermal cells. Immunofluorescence labelling of plant microtubules and microfilaments showed only limited alterations in the peripheral cytoskeleton of epidermal cells during early stages of fungal interaction with the wild type. Later, microtubules and microfilaments enveloped the growing hypha, while the host cell nucleus moved close to the fungus. In contrast, epidermal cells of the mutant responded with disorganisation and disassembly of microtubules and microfilaments before and during fungal penetration attempts. The fungus penetrated only as far as to epidermal cells, whose cytoplasm became devoid of tubulin and actin, suggesting cell death. The close relationship between host cytoskeleton organisation and compatibility with the fungus suggests that a functional Ljsym4 gene is necessary for correct reorganisation of the epidermal cell cytoskeleton in the presence of the fungus and for avoiding hypersensitivity-like reactions.

Extracellular polysaccharides are involved in the attachment of Azospirillum brasilense and Rhizobium leguminosarum to arbuscular mycorrhizal structures

Arbuscular mycorrhizal (AM) fungi, one of the most important component of the soil microbial community, establish physical interactions with naturally occurring and genetically modified bacterial biofertilizers and biopesticides, commonly referred to as plant growth-promoting rhizobacteria (PGPR). We have used a genetic approach to investigate the bacterial components possibly involved in the attachment of two PGPR (Azospirillum and Rhizobium) to AM roots and AM fungal structures. Mutants affected in extracellular polysaccharides (EPS) have been tested in in vitro adhesion assays and shown to be strongly impaired in the attachment to both types of surfaces as well as to quartz fibers. Anchoring of rhizobacteria to AM fungal structures may have special ecological and biotechnological significance because it may facilitate colonisation of new rhizospheres by the bacteria, and may be an essential trait for the development of mixed inocula.

A combined morphological and molecular approach to characterize isolates of arbuscular mycorrhizal fungi in Gigaspora (Glomales)

•  Morphological features of resting spores and information from nucleotide sequences of ribosomal RNA were used to characterize seven mycorrhizal fungal isolates in Gigaspora from different geographical areas. •  Detailed observations were made under the light microscope on single spores mounted in Melzer's reagent and polyvinyl alcohol-lactic acid-glycerol medium to resolve size, colour and cell wall structures. Neighbour-joining analyses were carried out on a portion of the 18S gene and on the internal transcribed spacer (ITS) region amplified by PCR from multisporal DNA preparations. •  Combined data allowed us to design oligonucleotides that unambiguously distinguished Gi. rosea from Gi. margarita and Gi. gigantea and also identified two isolates as Gi. rosea that had been previously diagnosed as Gi. margarita. ITS sequences revealed substantial genetic variability within clones of a single isolate of Gi. rosea as well as among geographically disjunct Gi. rosea isolates. •  The results show how complementary morphological and molecular data can clarify relationships among species of low morphological divergence. Sequence information allowed the extent of genetic divergence within these species to be investigated and provided useful PCR primers for detection and identification.

Prognostic indicators of local recurrence in patients operated for rectal cancer

BACKGROUND/AIMS

To identify subgroups of patients at high risk of local relapse after curative surgery for rectal cancer.

METHODOLOGY

Thirty-five variables of 216 patients observed from January 1987 to December 1995 were retrospectively analyzed according to univariate and multivariate methods. Median follow-up was 38 months.

RESULTS

High and moderate grade (P = 0.0001), Size > or = 5 cm (P = 0.013), lymph nodes involvement (P = 0.002) and patients with locally advanced rectal cancer underwent extensive surgery and postoperative radiation significantly increased local relapse; whereas surgical procedure and experience of surgeons had no influence.

CONCLUSIONS

The above-mentioned prognostic factors of rectal cancer that show a risk of local relapse 2- to 3.5-times higher than comparative conditions could be useful in identifying subgroups of patients at high risk for local recurrence. These patients should undergo a careful selection according to risk factors of relapse in order to increase local control of disease performing "optimal" primary surgery, effective postoperative radiation and tailored follow-up.

Impact of biocontrol Pseudomonas fluorescens CHA0 and a genetically modified derivative on the diversity of culturable fungi in the cucumber rhizosphere

Little is known about the effects of Pseudomonas biocontrol inoculants on nontarget rhizosphere fungi. This issue was addressed using the biocontrol agent Pseudomonas fluorescens CHA0-Rif, which produces the antimicrobial polyketides 2,4-diacetylphloroglucinol (Phl) and pyoluteorin (Plt) and protects cucumber from several fungal pathogens, including Pythium spp., as well as the genetically modified derivative CHA0-Rif(pME3424). Strain CHA0-Rif(pME3424) overproduces Phl and Plt and displays improved biocontrol efficacy compared with CHA0-Rif. Cucumber was grown repeatedly in the same soil, which was left uninoculated, was inoculated with CHA0-Rif or CHA0-Rif(pME3424), or was treated with the fungicide metalaxyl (Ridomil). Treatments were applied to soil at the start of each 32-day-long cucumber growth cycle, and their effects on the diversity of the rhizosphere populations of culturable fungi were assessed at the end of the first and fifth cycles. Over 11,000 colonies were studied and assigned to 105 fungal species (plus several sterile morphotypes). The most frequently isolated fungal species (mainly belonging to the genera Paecilomyces, Phialocephala, Fusarium, Gliocladium, Penicillium, Mortierella, Verticillium, Trichoderma, Staphylotrichum, Coniothyrium, Cylindrocarpon, Myrothecium, and Monocillium) were common in the four treatments, and no fungal species was totally suppressed or found exclusively following one particular treatment. However, in each of the two growth cycles studied, significant differences were found between treatments (e.g., between the control and the other treatments and/or between the two inoculation treatments) using discriminant analysis. Despite these differences in the composition and/or relative abundance of species in the fungal community, treatments had no effect on species diversity indices, and species abundance distributions fit the truncated lognormal function in most cases. In addition, the impact of treatments at the 32-day mark of either growth cycle was smaller than the effect of growing cucumber repeatedly in the same soil.

Molecular and morphological characterization of Tuber magnatum mycorrhizas in a long-term survey

Tuber magnatum Pico is an ectomycorrhizal fungus whose mycorrhizas can be barely distinguished morphologically from those of other related white truffles. Here we describe the use of specific primers based on the T. magnatum ITS sequence for screening mycorrhizas from a large number of growth chambers, greenhouse and nursery samples taken in a long-term survey. This molecular identification technique enabled a new morphological characterization to be set up for T. magnatum mycorrhizas.

Mucoid mutants of the biocontrol strain pseudomonas fluorescens CHA0 show increased ability in biofilm formation on mycorrhizal and nonmycorrhizal carrot roots

Extracellular polysaccharides play an important role in the formation of bacterial biofilms. We tested the biofilm-forming ability of two mutant strains with increased production of acidic extracellular polysaccharides compared with the wild-type biocontrol strain Pseudomonas fluorescens CHA0. The anchoring of bacteria to axenic nonmycorrhizal and mycorrhizal roots as well as on extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices was investigated. The nonmucoid wild-type strain P. fluorescens CHA0 adhered very little on all surfaces, whereas both mucoid strains formed a dense and patchy bacterial layer on the roots and fungal structures. Increased adhesive properties of plant-growth-promoting bacteria may lead to more stable interactions in mixed inocula and the rhizosphere.

Nitrogen fixation genes in an endosymbiotic Burkholderia strain

In this paper we report the identification and characterization of a DNA region containing putative nif genes and belonging to a Burkholderia endosymbiont of the arbuscular mycorrhizal fungus Gigaspora margarita. A genomic library of total DNA extracted from the fungal spores was also representative of the bacterial genome and was used to investigate the prokaryotic genome. Screening of the library with Azospirillum brasilense nifHDK genes as the prokaryotic probes led to the identification of a 6,413-bp region. Analysis revealed three open reading frames encoding putative proteins with a very high degree of sequence similarity with the two subunits (NifD and NifK) of the component I and with component II (NifH) of nitrogenase from different diazotrophs. The three genes were arranged in an operon similar to that shown by most archaeal and bacterial diazotrophs. PCR experiments with primers designed on the Burkholderia nifHDK genes and Southern blot analysis demonstrate that they actually belong to the genome of the G. margarita endosymbiont. They offer, therefore, the first sequence for the nif operon described for Burkholderia. Reverse transcriptase PCR experiments with primers designed on the Burkholderia nifH and nifD genes and performed on total RNA extracted from spores demonstrate that the gene expression was limited to the germination phase. A phylogenetic analysis performed on the available nifK sequences placed the endosymbiotic Burkholderia close to A. brasilense.

Immunolocalization of hydrophobin HYDPt-1 from the ectomycorrhizal basidiomycete Pisolithus tinctorius during colonization of Eucalyptus globulus roots

•  The immunolocalization of one of the hydrophobins of Pisolithustinctorius (HYDPt-1) is reported. Hydrophobin proteins play key roles in adhesion and aggregation of fungal hyphae, and it is already known that formation of ectomycorrhizas on eucalypt roots enhances the accumulation of hydrophobin mRNAs in the mycelium of Pisolithus tinctorius. •  Purification of SDS-insoluble proteins from the mycelium of P. tinctorius showed the presence of a 13 kDa polypeptide with properties of class I hydrophobin. •  Polyconal antibodies were raised against a recombinant HYDPt-1 polypeptide, and these were used for immunofluorescence-coupled transmission electron microscopy. •  HYDPt-1 is a cell wall protein located at the surface of the hyphae with no preferential accumulation in the fungal cells of the different tissues of the ectomycorrhiza (i.e. extraradical hyphae, mantle or Hartig net).

Differential expression of chitin synthase III and IV mRNAs in ascomata of Tuber borchii Vittad

A full-length genomic clone encoding a class III chitin synthase (CHS) and one DNA fragment corresponding to a class IV CHS were isolated from the mycorrhizal fungus Tuber borchii and used for an extensive expression analysis, together with a previously identified DNA fragment corresponding to a class II CHS. All three Chs mRNAs are constitutively expressed in vegetative mycelia, regardless of the age, mode of growth, and proliferation capacity of the hyphae. A strikingly different situation was observed in ascomata, where class III and IV, but not class II, mRNAs are differentially expressed in a maturation stage-dependent manner and accumulate, respectively, in sporogenic and vegetative hyphae. These data, the first on the expression of distinct Chs mRNAs during fruitbody development, point to the different cellular roles that can be played by distinct chitin synthases in the differentiation of spores of sexual origin (CHS III) or in ascoma enlargement promoted by the growth of vegetative hyphae (CHS IV).

The Lotus japonicus LjSym4 gene is required for the successful symbiotic infection of root epidermal cells

The role of the Lotus japonicus LjSym4 gene during the symbiotic interaction with Mesorhizobium loti and arbuscular mycorrhizal (AM) fungi was analyzed with two mutant alleles conferring phenotypes of different strength. Ljsym4-1 and Ljsym4-2 mutants do not form nodules with M. loti. Normal root hair curling and infection threads are not observed, while a nodC-dependent deformation of root hair tips indicates that nodulation factors are still perceived by Ljsym4 mutants. Fungal infection attempts on the mutants generally abort within the epidermis, but Ljsym4-1 mutants allow rare, successful, infection events, leading to delayed arbuscule formation. On roots of mutants homozygous for the Ljsym4-2 allele, arbuscule formation was never observed upon inoculation with either of the two AM fungi, Glomus intraradices or Gigaspora margarita. The strategy of epidermal penetration by G. margarita was identical for Ljsym4-2 mutants and the parental line, with appressoria, hyphae growing between two epidermal cells, penetration of epidermal cells through their anticlinal wall. These observations define a novel, genetically controlled step in AM colonization. Although rhizobia penetrate the tip of root hairs and AM fungi access an entry site near the base of epidermal cells, the LjSym4 gene is necessary for the appropriate response of this cell type to both microsymbionts. We propose that LjSym4 is required for the initiation or coordinated expression of the host plant cell's accommodation program, allowing the passage of both microsymbionts through the epidermis layer.

Detection and identification of bacterial endosymbionts in arbuscular mycorrhizal fungi belonging to the family Gigasporaceae

Intracellular bacteria have been found previously in one isolate of the arbuscular mycorrhizal (AM) fungus Gigaspora margarita BEG 34. In this study, we extended our investigation to 11 fungal isolates obtained from different geographic areas and belonging to six different species of the family Gigasporaceae. With the exception of Gigaspora rosea, isolates of all of the AM species harbored bacteria, and their DNA could be PCR amplified with universal bacterial primers. Primers specific for the endosymbiotic bacteria of BEG 34 could also amplify spore DNA from four species. These specific primers were successfully used as probes for in situ hybridization of endobacteria in G. margarita spores. Neighbor-joining analysis of the 16S ribosomal DNA sequences obtained from isolates of Scutellospora persica, Scutellospora castanea, and G. margarita revealed a single, strongly supported branch nested in the genus Burkholderia.

Development and good breeding in legume models: poise and peas?: Molecular Genetics of Model Legumes

John Innes Centre, Norwich, UK, June 2000 Genomics research involving legumes, an area that is attracting major funding, has two distinct branches - work involving model species, and work involving crops. This meeting aimed to stimulate communication between these two groups. The major research areas covered included leaf, flower and seed development, establishment of symbioses, pathogen interactions and applied aspects (from the conservation of legume ecotypes to products required by the market).

TMpcp: a Tuber magnatum gene which encodes a putative mitochondrial phosphate carrier

Little is known about the genome of Tuber, Ascomycetes which comprise a number of ectomycorrhizal species. Screening of a genomic library of Tuber magnatum led to identification of a chitin synthase gene (chs). On sequencing upstream of it in the same phage, we found a 2000 bp long fragment that proved to contain a hypothetical gene with high homology with mitochondrial phosphate carriers from human and bovine heart, and from Saccharomyces cerevisiae. The sequence contains two putative introns and its open reading frame encodes for a protein 305 amino acids long. A primary sequence analysis revealed 6 hydrophobic segments and a signature pattern, similar to that of other mitochondrial carriers.

[Richter's hernia: a clinical case and the clinico-therapeutic considerations]

The authors report a case of Richter's hernia. They underline main clinical and therapeutic patterns, emphasizing the need of an early diagnosis and surgery. This is a hernia of abdominal wall with partial entrapment of bowel wall (antimesenteric site) through a small ring. The incidence increased in the last years because of diffusion of laparoscopic techniques. Richter's hernia could be asymptomatic for a long time or show vanish sign. Sometimes this hernia can be diagnosed during surgery. The clinical signs are conclamated if hernia is complicated by strangulation. High mortality is justified by performing too late diagnosis and operation.

A Burkholderia Strain Living Inside the Arbuscular Mycorrhizal Fungus Gigaspora margarita Possesses the vacB Gene, Which Is Involved in Host Cell Colonization by Bacteria

The arbuscular mycorrhizal (AM) fungus Gigaspora margarita harbors a resident population of endosymbiontic Burkholderia in its cytoplasm. Nothing is known about the acquisition of such bacteria and about the molecular bases which allow colonization of the fungus. We wondered whether the intracellular Burkholderia strain possesses genetic determinants involved in colonization of a eukaryotic cell. Using degenerated oligonucleotide primers for vacB, a gene involved in host cell colonization by pathogenic bacteria, an 842 bp DNA fragment was cloned, sequenced, and identified as a part of the vacB gene in Burkholderia sp. The insert was used as a probe to screen a fungal library that, because of the presence of intracellular Burkholderia cells, was also representative of the bacterial genome. The complete nucleotide sequence of vacB and flanking genes was determined. The bacterial origin of this genomic region was established by PCR, using specific vacB primers on DNA from Gigasporaceae that did or did not contain cytoplasmic Burkholderia, as well as on DNA from other bacteria, including free-living Burkholderia. We hypothesize that the vacB gene is part of a new genetic region acquired by a rhizospheric Burkholderia strain, which became able to establish a symbiotic interaction with the AM fungus G. margarita.

Is intensive follow-up really able to improve prognosis of patients with local recurrence after curative surgery for rectal cancer?

BACKGROUND

Because more than 90% of local recurrences after curative surgery for rectal cancer appear within the first 36 months after surgery, an intensive and strict follow-up program during this period could improve early diagnosis and, thus, prognosis of patients.

METHODS

Of the 216 patients who underwent surgery for rectal cancer, 127 entered an intensive follow-up program (median follow-up: 42 months); the clinical outcome of the remaining 89 patients was reconstructed with the help of their general practitioners.

RESULTS

Fifty eight (26.8%) of the 216 patients who were treated with curative surgery alone developed a local recurrence; pelvic recurrences were prevalent. Eleven (30.5%) of the 36 patients who had recurrence during follow-up, and 6 of the 22 who had not undergone follow-up, had a reoperation with curative intent; the median survival was 19 months vs. 8 months, respectively (P = ns). Four (44.4%) curative reoperations were performed on the 9 asymptomatic patients and in 13 (26.5%) of the 49 cases with symptomatic local recurrences. Median survival was 15 months vs. 14 months, respectively (P = n.s). All patients except one (living after 42 months from reoperation) died within 48 months.

CONCLUSIONS

In our study, adherence to a strict follow-up program unfortunately proved to be ineffective for improving long-term survival for patients who underwent reoperation with curative intent.

A novel class of ectomycorrhiza-regulated cell wall polypeptides in Pisolithus tinctorius

Development of the ectomycorrhizal symbiosis leads to the aggregation of fungal hyphae to form the mantle. To identify cell surface proteins involved in this developmental step, changes in the biosynthesis of fungal cell wall proteins were examined in Eucalyptus globulus-Pisolithus tinctorius ectomycorrhizas by two-dimensional polyacrylamide gel electrophoresis. Enhanced synthesis of several immunologically related fungal 31- and 32-kDa polypeptides, so-called symbiosis-regulated acidic polypeptides (SRAPs), was observed. Peptide sequences of SRAP32d were obtained after trypsin digestion. These peptides were found in the predicted sequence of six closely related fungal cDNAs coding for ectomycorrhiza up-regulated transcripts. The PtSRAP32 cDNAs represented about 10% of the differentially expressed cDNAs in ectomycorrhiza and are predicted to encode alanine-rich proteins of 28.2 kDa. There are no sequence homologies between SRAPs and previously identified proteins, but they contain the Arg-Gly-Asp (RGD) motif found in cell-adhesion proteins. SRAPs were observed on the hyphal surface by immunoelectron microscopy. They were also found in the host cell wall when P. tinctorius attached to the root surface. RNA blot analysis showed that the steady-state level of PtSRAP32 transcripts exhibited a drastic up-regulation when fungal hyphae form the mantle. These results suggest that SRAPs may form part of a cell-cell adhesion system needed for aggregation of hyphae in ectomycorrhizas.

Identification of a putative P-transporter operon in the genome of a Burkholderia strain living inside the arbuscular mycorrhizal fungus Gigaspora margarita

This article reports the identification of a putative P-transporter operon in the genome of a Burkholderia sp. living in the cytoplasm of the arbuscular mycorrhizal fungus Gigaspora margarita. Its presence suggests that Burkholderia sp. has the potential for P uptake from this environment. This finding raises new questions concerning the importance of intracellular bacteria for mycorrhizal symbiosis.

Cell wall proteins of the ectomycorrhizal basidiomycete Pisolithus tinctorius: identification, function, and expression in symbiosis

Specific cell-cell and cell-substrate interactions direct the growth of ectomycorrhizal fungi to their host root targets. These elaborate mechanisms lead to the differentiation of distinct multihyphal structures, the mantle, and the Hartig net. In the ectomycorrhizal basidiomycete Pisolithus tinctorius, the use of two-dimensional gel electrophoresis, immunocytochemical microscopy, and RNA blot analysis has demonstrated the differential expression of cell wall proteins (CWPs), such as hydrophobins, adhesins, and mannoproteins, during symbiotic interaction. In other fungi, these CWPs have been suggested to play a role in hyphae aggregation, intracellular signaling cascades, and cytoskeletal changes. The recent cloning of the genes for several of these CWPs in P. tinctorius allows us to address their function in symbiosis. This review summarizes our knowledge of CWPs in P. tinctorius and considers parallels with other biotrophic fungi as a possible framework for future work.

Local control after curative surgery for cancer of the extraperitoneal rectum. Twenty years of experience

A retrospective study was carried out in 264 patients with low rectal cancer surgically treated with curative intent from January 1975 to December 1995 to analyze the influence of stapling devices on surgical and disease outcome. Patients were classified as follows: group 1 underwent surgery from 1975 to 1980, when staplers were not employed, and group 2 from 1981 to 1995, when stapling devices were routinely used. The use of stapling devices determined a corresponding increase in low anterior resection (LAR) and a decrease in postoperative mortality. A statistically significant difference in local recurrence rate between abdominoperineal resection (APR) patients and LAR sutured cases of group 1 was observed. In T3, N+ cases local recurrence rate was comparable in APR patients and LAR cases with stapled anastomosis. Improved local control occurred in stapled group 2 patients which was independent of the distal clearance. Although APR still plays an important role in treatment of lower rectal cancer, results indicated that a similar outcome after stapled LAR can also be expected in locally advanced carcinoma of the distal rectum, if accurate excision of perirectal tissue is carried out.

Intrasporal variability of ribosomal sequences in the endomycorrhizal fungus Gigaspora margarita

The sequence variability of the ribosomal internal transcribed spacer (ITS) region, which comprises the 5.8 gene and the flanking regions ITS1 and ITS2, was investigated in the arbuscular mycorrhizal fungus Gigaspora margarita. DNA analysis of a multispore preparation and three single spores led to the identification of 11 slightly different sequences (three variants within a single spore), indicating substantial intersporal and intrasporal genetic variability (up to 9% sequence divergence). The sequence variations inside a single spore may be higher than that observed between spores. Even so, primers designed on the ITS1 and ITS2 regions identified Gi. margarita isolates and detected the endophyte during colonization.

[Renal hemangiopericytoma. Anatomo-pathologic and clinico-therapeutic considerations. A case report]

The Authors report a case of renal hemangiopericytoma, whose interest is related to the extreme rarity (24 cases reported until today), its insidious growth, the late in diagnosis, its uncertain clinical-biological evolution, not always predictable. Considering chemotherapy and radiotherapy ineffectiveness, an adequate treatment for such a neoplasm requires the surgical therapy, which must be followed by a careful follow-up.

Chitin synthase genes in the arbuscular mycorrhizal fungus Glomus versiforme: full sequence of a gene encoding a class IV chitin synthase

Chitin synthase genes of the arbuscular mycorrhizal fungus Glomus versiforme were sought in an investigation of the molecular basis of fungal growth. Three DNA fragments (Gvchs1, Gvchs2 and Gvchs3) corresponding to the conserved regions of distinct chitin synthase (chs) genes were amplified by means of the polymerase chain reaction (PCR) with two sets of degenerate primers. Gvchs1 and Gvchs2 encode two class I chitin synthases, whereas Gvchs3 encodes a class IV chitin synthase. A genomic library was used to obtain the Gvchs3 complete gene (1194 amino acids), which shows a very close similarity to the class IV chitin synthase from Neurospora crassa.

Cytoskeleton-related proteins in tobacco mycorrhizal cells: gamma-tubulin and clathrin localisation

Plant cytoskeletal components respond to the penetration of both pathogenic and symbiotic fungi with a new organization of microtubules and microfilaments. To determine the origin and potential role of microtubule arrays previously observed in tobacco cells colonised by an arbuscular mycorrhizal fungus, we have investigated the patterns of gamma-tubulin and clathrin in uninfected and mycorrhizal cells with immunofluorescence techniques. Antibody against gamma-tubulin revealed microtubule organising centers (MTOC) along the nuclear envelope and along the host membrane that surrounds the plant/fungus interface, while clathrin was observed along the peripheral and perifungal membranes, as well as along a tubular system of endomembranes.