Biology subjects

Walser, J.-C.

Publications and source records attributed to Walser, J.-C..

3 recordsLinked to original sources

bioRxiv2018

SPECIES-SPECIFIC ROOT MICROBIOTA DYNAMICS IN RESPONSE TO PLANT-AVAILABLE PHOSPHORUS

O_LIPhosphorus (P) is a limiting element for plant growth. Several root microbes, including arbuscular mycorrhizal fungi (AMF), have the capacity to improve plant nutrition and their abundance is known to depend on P fertility. However, how complex root-associated bacterial and fungal communities respond to changes in P availability remains ill-defined.\nC_LIO_LIWe manipulated the availability of soil P in pots and compared the root microbiota of non-mycorrhizal Arabidopsis with mycorrhizal Petunia plants. Root bacteria and fungi were profiled using ribosomal operon gene fragment sequencing, we searched for P sensitive microbes and tested whether a P sensitive core microbiome could be identified.\nC_LIO_LIRoot microbiota composition varied substantially by P availability. A P sensitive core microbiome was not identified as different bacterial and fungal groups responded to low-P conditions in Arabidopsis and Petunia. P sensitive microbes included Mortierellomycotina in Arabidopsis, while these were AMF and their symbiotic endobacteria in Petunia. Of note, their P-dependent root colonization was reliably quantified by sequencing.\nC_LIO_LIThe species-specific root microbiota dynamics suggest that Arabidopsis and Petunia evolved different microbial associations under the selection pressure of low P availability. This implies that the development of microbial products that improve P availability requires the consideration of host-species specificity.\nC_LI

plant biology↗

bioRxiv2018

Environmental sources of bacteria and genetic variation in behavior influence host-associated microbiota

In many organisms, host-associated microbial communities are acquired horizontally after birth. This process is believed to be shaped by a combination of environmental and host genetic factors. We examined whether genetic variation in animal behavior could affect the composition of the animals microbiota in different environments. The freshwater crustacean Daphnia magna is primarily planktonic, but exhibits variation in the degree to which it browses in benthic sediments. We performed an experiment with clonal lines of D. magna showing different levels of sediment-browsing intensity exposed to either bacteria-rich or bacteria-poor sediment or whose access to sediments was prevented. We find that the bacterial composition of the environment and genotype-specific browsing intensity together influence the diversity and composition of the Daphnia-associated bacterial community. Exposure to more diverse bacteria did not lead to a more diverse microbiome, but greater abundances of environment-specific bacteria were found associated with host genotypes that exhibited greater browsing behavior. Our results indicate that individual behavior can mediate genotype-by-environment interaction effects on microbiome composition.\n\nSummary statementGenetic differences in Daphnia behavior contribute to the amount of environmental bacteria present in their microbiome

evolutionary biology↗

bioRxiv2018

Genome-wide scans of selection highlight the impact of biotic and abiotic constraints in natural populations of the model grass Brachypodium distachyon.

Grasses are essential plants for ecosystem functioning. Quantifying the selective pressures that act on natural variation in grass species is therefore essential regarding biodiversity maintenance. In this study, we investigate the selection pressures that act on two distinct populations of the grass model Brachypodium distachyon without prior knowledge about the traits under selection. We took advantage of whole-genome sequencing data produced for 44 natural accessions of B. distachyon and used complementary genome-wide scans of selection (GWSS) methods to detect genomic regions under balancing and positive selection. We show that selection is shaping genetic diversity at multiple temporal and spatial scales in this species and affects different genomic regions across the two populations. Gene Ontology annotation of candidate genes reveals that pathogens may constitute important factors of positive and balancing selection in Brachypodium distachyon. We eventually cross-validated our results with QTL data available for leaf-rust resistance in this species and demonstrate that, when paired with classical trait mapping, GWSS can help pinpointing candidate genes for further molecular validation. Thanks to a near-base perfect reference genome and the large collection of freely available natural accessions collected across its natural range, B. distachyon appears as a prime system for studies in ecology, population genomics and evolutionary biology.

evolutionary biology↗