Biology subjects

Thouin, J.

Publications and source records attributed to Thouin, J..

4 recordsLinked to original sources

bioRxiv2025

Comparing the Seasonal Diets of Buff-tailed Bumblebees and Honey Bees in a Forest Landscape: A Metabarcoding Approach

The declining diversity of pollinating insects is a major threat to ecosystem conservation, pollination services, and global food security. Honeybees (Apis mellifera L.) dominate managed pollination, but their dominance can affect other pollinators. Competition for resources can lead to decreased foraging success and survival rates for wild bees, especially bumblebees. This study explores the dietary composition of honeybees and buff-tailed bumblebees (Bombus terrestris L.) using metabarcoding techniques with three primers (ITS2, TrnLgh, and TrnLch) in Avensan, France. Primers detected different species pools, indicating a high diversity of plants visited by both species - including some false positives results inherent to metabarcoding methods. The "primer" effect was more important than the "pollinator" effect in segregating plants found. The Schoener index revealed a slight diet overlap in plant species used by honeybees and bumblebees, depending on the primer. Correspondence analyses showed a high segregation between species associated with honeybees or with bumblebees, regardless of the primer. The metabarcoding technique was found to be accurate in separating pollinator food niches, despite some biases of this technique: this result is not comparable with previous literature studying the diets of these two species, as traditional [fi]eld studies are needed to complement it and overcome these biases. To conclude, this study provides a fast and inexpensive approach to study pollinators floral resources sharing in the same geographical area and time scale, and provide insights to improve metabarcoding effectiveness in order to better describe diet niches.

ecology↗

bioRxiv2023

Simultaneous tracking of near-isogenic bacterial strains in synthetic Arabidopsis microbiota by chromosomally-integrated barcodes

DNA amplicon-based microbiota profiling currently relies on polymorphisms in microbial marker genes to estimate species diversity and abundance. However, this technique cannot resolve genetic differences among microbial individuals of the same species. We report here the development of modular bacterial tags (MoBacTags) encoding DNA barcodes. These tags facilitate tracking of near-isogenic bacterial commensals in synthetic communities (SynComs), which allow assessment of the contributions of individual bacterial genes to root microbiota establishment in Arabidopsis thaliana. Chromosomally-integrated DNA barcodes are co-amplified with endogenous marker genes of the community by integrating corresponding primer binding sites into the barcode. We generated MoBacTag-labeled strains of wild-type Pseudomonas capeferrum WCS358 and of pqqF and cyoB mutants with known defects in gluconic acid-mediated host immunosuppression and validated reduced root colonization of both mutants in a 15-member synthetic microbiota. We detected a reduced SynCom load on roots in the presence of the WCS358:pqqF mutant, but not WCS358:cyoB, revealing distinct pqqF and cyoB activities in a community context. Using MoBacTags, we also show that WCS358 pqqF mutant-specific colonization and community establishment is not trans-complemented by wild-type WCS358. Given that gluconic acid production in P. capeferrum is indirectly abolished in the pqqF mutant by disruption of pyrroloquinoline quinone (PQQ) biosynthesis, we propose that drastic changes in the root-associated community result from depletion of the cofactor PQQ, which might serve as a common good during root microbiota establishment. Our proof-of-principle experiments illustrate how MoBacTags can be applied to assess scaling of individual bacterial genetic determinants in the plant microbiota.

microbiology↗

bioRxiv2019

The Medicago truncatula HKT family: Ion transport properties and regulation of expression upon abiotic stresses and symbiosis

Soil salinity is one of the most important abiotic stresses affecting plant growth. In legumes, symbiotic nitrogen fixation in nodules is affected by salt stress, and salinity tolerance is variable among species. Genes from the High affinity K+ Transporter (HKT) family are known to play crucial roles in salt stress tolerance in different plant species. In legumes these transporters are still very poorly characterized.. Here we study the HKT transporter family from the model legume Medicago trunacatula, which is moderately tolerant to salinity. The genome of this species comprises five HKT genes, hereafter named MtHKT1;1 to MtHKT1;5. Phylogenetic analysis indicated that the MtHKT polypeptides belong to HKT subfamily 1. Three members (MtHKT1;2, MtHKT1;4 and MtHKT1;5) of the Medicago truncatula family were cloned and expressed in Xenopus oocytes. Their electrophysiological properties revealed a permeability 10 times higher for Na+ than for K+ and varying rectification properties. Expression analyses of the three MtHKT genes under different biotic and abiotic conditions suggested that MtHKT1;5 is the main transporter from this family in the root, the three genes sharing a decrease of expression in drought and salt stress conditions in non inoculated plants as well as plants inoculated with rhizobia. In the shoot, the three MtHKT would be present at similar levels independently on the applied stresses. Based on biomass and ion content analysis, the nodule appeared as the most sensitive organ to the applied salt and drought stresses. The level of expression of the three MtHKT genes was strongly decreased by both stresses in the nodule.

plant biology↗

bioRxiv2019

Medicago truncatula possesses a single Shaker outward K+ channel: functional characterization and roles in planta

The model legume Medicago truncatula possesses a single outward Shaker K+ channel, while Arabidopsis thaliana possesses two channels of this type, named SKOR and GORK, the former having been shown to play a major role in K+ secretion into the xylem sap in the root vasculature and the latter to mediate the efflux of K+ across the guard cell membrane upon stomatal closure. Here we show that the expression pattern of the single M. truncatula outward Shaker channel, which has been named MtGORK, includes the root vasculature, guard cells and root hairs. As shown by patch-clamp experiments on root hair protoplasts, besides the Shaker-type slowly-activating outwardly-rectifying K+ conductance encoded by MtGORK, a second K+-permeable conductance, displaying fast activation and weak rectification, can be expressed by M. truncatula. A KO mutation resulting in absence of MtGORK activity is shown to weakly reduce K+ translocation to shoots, and only in plants engaged in rhizobial symbiosis, but to strongly affect the control of stomatal aperture and transpitational water loss. In legumes, the early electrical signaling pathway triggered by Nod Factor perception is known to comprise a short transient depolarization of the root hair plasma membrane. In absence of MtGORK functional expression, while the rate of the membrane repolarization is shown to be decreased by about 3 times, this defect is without any consequence on infection thread development and nodule production, indicating that the plant capacity to engage rhizobial symbiosis does not require integrity of the early electrical signaling events.

plant biology↗