Comparative metabolomic study of fungal foliar endophytes and their long-lived host Astrocaryum sciophilum: a model for exploring the chemodiversity of host-microbe interactions

Introduction

In contrast to the dynamics observed in plant/pathogen interactions, endophytic fungi have the capacity to establish enduring associations within their hosts, leading to the development of a mutually beneficial relationship that relies on specialized chemical interactions. Research indicates that the presence of endophytic fungi has the ability to significantly modify the chemical makeup of the host organism. Our hypothesis proposes the existence of a reciprocal exchange of chemical signals between plants and fungi, facilitated by specialized chemical processes that could potentially manifest within the tissues of the host. This research aimed to precisely quantify the portion of the cumulative fungal endophytic community's metabolome detectable within host leaves, and tentatively evaluate its relevance to the host-endophyte interplay. The understory palm Astrocaryum sciophilum (Miq.) Pulle was used as a interesting host plant because of its notable resilience and prolonged life cycle, in a tropical ecosystem.

Method

Using advanced metabolome characterization, including UHPLC-HRMS/MS and molecular networking, the study explored enriched metabolomes of both host leaves and 15 endophytic fungi. The intention was to capture a metabolomic "snapshot" of both host and endophytic community, to achieve a thorough and detailed analysis.

Results and discussion

This approach yielded an extended MS-based molecular network, integrating diverse metadata for identifying host- and endophyte-derived metabolites. The exploration of such data (>24000 features in positive ionization mode) enabled effective metabolome comparison, yielding insights into cultivable endophyte chemodiversity and occurrence of common metabolites between the holobiont and its fungal communities. Surprisingly, a minor subset of features overlapped between host leaf and fungal samples despite significant plant metabolome enrichment. This indicated that fungal metabolic signatures produced in vitro remain sparingly detectable in the leaf. Several classes of primary metabolites were possibly shared. Specific fungal metabolites and/or compounds of their chemical classes were only occasionally discernible in the leaf, highlighting endophytes partial contribution to the overall holobiont metabolome. To our knowledge, the metabolomic study of a plant host and its microbiome has rarely been performed in such a comprehensive manner. The general analytical strategy proposed in this paper seems well-adapted for any study in the field of microbial- or microbiome-related MS and can be applied to most host-microbe interactions.

Paleoenvironments shaped the exchange of terrestrial vertebrates across Wallace's Line

Faunal turnover in Indo-Australia across Wallace's Line is one of the most recognizable patterns in biogeography and has catalyzed debate about the role of evolutionary and geoclimatic history in biotic interchanges. Here, analysis of more than 20,000 vertebrate species with a model of geoclimate and biological diversification shows that broad precipitation tolerance and dispersal ability were key for exchange across the deep-time precipitation gradient spanning the region. Sundanian (Southeast Asian) lineages evolved in a climate similar to the humid "stepping stones" of Wallacea, facilitating colonization of the Sahulian (Australian) continental shelf. By contrast, Sahulian lineages predominantly evolved in drier conditions, hampering establishment in Sunda and shaping faunal distinctiveness. We demonstrate how the history of adaptation to past environmental conditions shapes asymmetrical colonization and global biogeographic structure.

Temperature-dependent evolutionary speed shapes the evolution of biodiversity patterns across tetrapod radiations

Biodiversity varies predictably with environmental energy around the globe, but the underlaying mechanisms remain incompletely understood. The evolutionary speed hypothesis predicts that environmental kinetic energy shapes variation in speciation rates through temperature- or life history-dependent rates of evolution. To test whether variation in evolutionary speed can explain the relationship between energy and biodiversity in birds, mammals, amphibians, and reptiles, we simulated diversification over 65 million years of geological and climatic change with a spatially explicit eco-evolutionary simulation model. We modelled four distinct evolutionary scenarios in which speciation-completion rates were dependent on temperature (M1), life history (M2), temperature and life history (M3), or were independent of temperature and life-history (M0). To assess the agreement between simulated and empirical data, we performed model selection by fitting supervised machine learning models to multidimensional biodiversity patterns. We show that a model with temperature-dependent rates of speciation (M1) consistently had the strongest support. In contrast to statistical inferences, which showed no general relationships between temperature and speciation rates in tetrapods, we demonstrate how process-based modelling can disentangle the causes behind empirical biodiversity patterns. Our study highlights how environmental energy has played a fundamental role in the evolution of biodiversity over deep time.

Coral reef fishes reveal strong divergence in the prevalence of traits along the global diversity gradient

Coral reefs are experiencing declines due to climate change and local human impacts. While at a local scale these impacts induce biodiversity loss and shifts in community structure, previous biogeographical analyses recorded consistent taxonomic structure of fish communities across global coral reefs. This suggests that regional communities represent a random subset of the global species and traits pool, whatever their species richness. Using distributional data on 3586 fish species and latest advances in species distribution models, we show marked gradients in the prevalence of size classes and diet categories across the biodiversity gradient. This divergence in trait structure is best explained by reef isolation during past unfavourable climatic conditions, with large and piscivore fishes better represented in isolated areas. These results suggest the risk of a global community re-organization if the ongoing climate-induced reef fragmentation is not halted.

Diversification of the cold-adapted butterfly genus Oeneis related to Holarctic biogeography and climatic niche shifts

Both geographical and ecological speciation interact during the evolution of a clade, but the relative contribution of these processes is rarely assessed for cold-dwelling biota. Here, we investigate the role of biogeography and the evolution of ecological traits on the diversification of the Holarctic arcto-alpine butterfly genus Oeneis (Lepidoptera: Satyrinae). We reconstructed the molecular phylogeny of the genus based on one mitochondrial (COI) and three nuclear (GAPDH, RpS5, wingless) genes. We inferred the biogeographical scenario and the ancestral state reconstructions of climatic and habitat requirements. Within the genus, we detected five main species groups corresponding to the taxonomic division and further paraphyletic position of Neominois (syn. n.). Next, we transferred O. aktashi from the hora to the polixenes species group on the bases of molecular relationships. We found that the genus originated in the dry grasslands of the mountains of Central Asia and dispersed over the Beringian Land Bridges to North America several times independently. Holarctic mountains, in particular the Asian Altai Mts. and Sayan Mts., host the oldest lineages and most of the species diversity. Arctic species are more recent, with Pliocene or Pleistocene origin. We detected a strong phylogenetic signal for the climatic niche, where one lineage diversified towards colder conditions. Altogether, our results indicate that both dispersal across geographical areas and occupation of distinct climatic niches promoted the diversification of the Oeneis genus.

Soil fungal communities of grasslands are environmentally structured at a regional scale in the Alps

Studying patterns of species distributions along elevation gradients is frequently used to identify the primary factors that determine the distribution, diversity and assembly of species. However, despite their crucial role in ecosystem functioning, our understanding of the distribution of below-ground fungi is still limited, calling for more comprehensive studies of fungal biogeography along environmental gradients at various scales (from regional to global). Here, we investigated the richness of taxa of soil fungi and their phylogenetic diversity across a wide range of grassland types along a 2800 m elevation gradient at a large number of sites (213), stratified across a region of the Western Swiss Alps (700 km(2)). We used 454 pyrosequencing to obtain fungal sequences that were clustered into operational taxonomic units (OTUs). The OTU diversity-area relationship revealed uneven distribution of fungal taxa across the study area (i.e. not all taxa are everywhere) and fine-scale spatial clustering. Fungal richness and phylogenetic diversity were found to be higher in lower temperatures and higher moisture conditions. Climatic and soil characteristics as well as plant community composition were related to OTU alpha, beta and phylogenetic diversity, with distinct fungal lineages suggesting distinct ecological tolerances. Soil fungi, thus, show lineage-specific biogeographic patterns, even at a regional scale, and follow environmental determinism, mediated by interactions with plants.

Evaluation of laparoscopic treatment of common bile duct stones in a prospective series of 505 patients: indications and results

BACKGROUND

The aim of this prospective study was the evaluation of the laparoscopic treatment of common bile duct stones (CBDS) and its indications.

METHODS

Five hundred five patients who underwent laparoscopic treatment of CBDS from October 1990 to September 2006 were included in the prospective study. The mean age of the patients was 63 years (range = 19-93). Four hundred fifteen patients were classified ASA I and ASA II and 90 were ASA III and ASA IV. CBDS were suspected or diagnosed preoperatively in 373 patients (73.8%) and diagnosed at intraoperative cholangiography (IOC) in 132 patients (26.2%). A transcystic duct extraction (TCDE) was attempted in 254 patients (50.4%) and a primary choledochotomy in 251 patients (49.6%). Biliary drainage after choledochotomy was used in 148 cases (48.8%).

RESULTS

TCDE was successful in 191 cases (75.2%). The 63 failures were managed by laparoscopic choledochotomy in 53 cases and by endoscopic sphincterotomy (ES) in 10 cases. A choledochotomy was thus performed in 304 patients and successful in 295 cases (97%). The nine failures were managed by six conversions to laparotomy (2%) and three postoperative ES. The overall success rate was 96.2%. The morbidity rate was 7.9% with 4.8% of local complications and 3.1% of general complications. The mortality rate was 1%. There were 14 residual stones (2.8%) that were managed by a second laparoscopy in two cases and by ES in 12 cases with four failures managed by laparotomy in one case and laparoscopy in three cases.

CONCLUSION

Laparoscopic management of CBDS was effective in more than 96% of cases and particularly safe in ASA I and ASA II patients. It has the advantage over ES followed by laparoscopic cholecystectomy (LS) to be a one-stage procedure.

Reoperation for persistent or recurrent primary hyperparathyroidism

AIM

To analyse the causes and outcome of reoperations for persistent or recurrent primary hyperparathyroidism (HPT).

MATERIALS AND METHODS

We reviewed the medical records of 38 patients who underwent reoperation between December 1965 and April 1997 for persistent or recurrent primary HPT. During this period of time, 1448 patients underwent operation for primary HPT, 294 for renal HPT and 58 for questionable disease, i. e. a total of 1800. In the 1448 cases of HPT, 22 patients were reoperated after a first cervicotomy in the institution, i. e. a first reoperation rate of 1.5%. Sixteen patients were referred after unsuccessful parathyroid surgery. Six patients were reoperated on twice and one patient seven times for a graft-dependent recurrence.

RESULTS

Reasons for failed parathyroid operations included tumour tissue in ectopic location (75%) or tumour tissue that had not been seen in normal position (19%), parathyreomatosis (2%), parathyroid cancer (2%) and graft-dependent hypercalcaemia (2%). Of the ectopic glands, 45 % were intrathymic, 12.5% intrathyroidal, 7.5% retro-oesophageal, 7.5% in the carotid sheath, 5% interthyrotracheal, 5% in the mediastinum (extrathymic), 5% in the aorto-pulmonary window, 2.5% undescended, 2.5% overdescended and 2.5% intertracheooesophageal. Of the patients, 38% had uniglandular lesions, 60% multiglandular lesions, and 2% parathyroid cancer. The histologically confirmed cause of HPT was adenoma in 50% of cases, hyperplasia in 38% and "normal" but overweight glands in 9.5%. Of the 38 patients studied, 15 presented one or more supernumerary glands (fifth to eighth gland). Reoperation was performed through a cervical incision in 82% of cases and using a mediastinal approach in 18% (8 median sternotomies, 1 thoracoscopy). The success rate of the reoperations was 92%. A total of 8% of patients suffered permanent unilateral vocal cord paralysis; 5% are definitely hypocalcaemic. The sensitivities of preoperative localization studies ranged from 69% for sestamibi scan and 63% for selective venous catheterization to 16% for computed tomography.

CONCLUSION

Repeated parathyroidectomy can be avoided in more than 98% of patients if an experienced surgeon performs bilateral cervical exploration during the initial parathyroid operation. For patients with persistent or recurrent primary HPT, preoperative localization studies and a focused surgical approach can result in a 92% success rate with a minimal complication rate.