Sesquiterpenes of the ectomycorrhizal fungus Pisolithus microcarpus alter root growth and promote host colonization.

Trees form symbioses with ectomycorrhizal (ECM) fungi, maintained in part through mutual benefit to both organisms. Our understanding of the signaling events leading to the successful interaction between the two partners requires further study. This is especially true for understanding the role of volatile signals produced by ECM fungi. Terpenoids are a predominant class of volatiles produced by ECM fungi. While several ECM genomes are enriched in the enzymes responsible for the production of these volatiles (i.e., terpene synthases (TPSs)) when compared to other fungi, we have limited understanding of the biochemical products associated with each enzyme and the physiological impact of specific terpenes on plant growth. Using a combination of phylogenetic analyses, RNA sequencing, and functional characterization of five TPSs from two distantly related ECM fungi (Laccaria bicolor and Pisolithus microcarpus), we investigated the role of these secondary metabolites during the establishment of symbiosis. We found that despite phylogenetic divergence, these TPSs produced very similar terpene profiles. We focused on the role of P. microcarpus terpenes and found that the fungus expressed a diverse array of mono-, di-, and sesquiterpenes prior to contact with the host. However, these metabolites were repressed following physical contact with the host Eucalyptus grandis. Exposure of E. grandis to heterologously produced terpenes (enriched primarily in γ -cadinene) led to a reduction in the root growth rate and an increase in P. microcarpus-colonized root tips. These results support a very early putative role of fungal-produced terpenes in the establishment of symbiosis between mycorrhizal fungi and their hosts.

Continuous non-invasive vs. invasive arterial blood pressure monitoring during neuroradiological procedure: a comparative, prospective, monocentric, observational study.

BACKGROUND: In the perioperative setting, the most accurate way to continuously measure arterial blood pressure (ABP) is using an arterial catheter. Surrogate methods such as finger cuff have been developed to allow non-invasive measurements and are increasingly used, but need further evaluation. The aim of this study is to evaluate the accuracy and clinical concordance between two devices for the measurement of ABP during neuroradiological procedure. METHODS: This is a prospective, monocentric, observational study. All consecutive patients undergoing a neuroradiological procedure were eligible. Patients who needed arterial catheter for blood pressure measurement were included. During neuroradiological procedure, ABP (systolic, mean and diatolic blood pressure) was measured with two different technologies: radial artery catheter and Nexfin. Bland-Altman and error grid analyses were performed to evaluate the accuracy and clinical concordance between devices. RESULTS: From March 2022 to November 2022, we included 50 patients, mostly ASA 3 (60%) and required a cerebral embolization (94%) under general anaesthesia (96%). Error grid analysis showed that 99% of non-invasive ABP measures obtained with the Nexfin were located in the risk zone A or B. However, 65.7% of hypertension events and 41% of hypotensive events were respectively not detected by Nexfin. Compared to the artery catheter, a significant relationship was found for SAP (r2 = 0.78) and MAP (r2 = 0.80) with the Nexfin (p < 0.001). Bias and limits of agreement (LOA) were respectively 9.6 mmHg (- 15.6 to 34.8 mmHg) and - 0.8 mmHg (- 17.2 to 15.6 mmHg), for SAP and MAP. CONCLUSIONS: Nexfin is not strictly interchangeable with artery catheter for ABP measuring. Further studies are needed to define its clinical use during neuroradiological procedure. TRIAL REGISTRATION: Clinicaltrials.gov, registration number: NCT05283824.