Biology subjects

Jacquemot, M.-P.

Publications and source records attributed to Jacquemot, M.-P..

5 recordsLinked to original sources

bioRxiv2026

Same visitors, different outcomes: floral phenotype gates pollinator-vectored nectar microbial establishment

The microbiome of nectar has the potential to modify flower chemistry and plant-pollinator interactions. How its assembly differs between diurnal and nocturnal guilds, and how it depends on the flower they visit, remains poorly resolved in crops. We conducted field assays using two commercial sunflower cultivars (Helianthus annuus) that differ markedly in nectar volume and sugar composition, under four pollinator access treatments. Diurnal pollinator access, whether continuous or daytime-only, resulted in a cultivar-dependent microbiome signature. In one cultivar, nectar communities were characterized by the dominance of specialist taxa such as the yeast Metschnikowia and the bacterium Acinetobacter. However, neither taxa established dominance in the nectar of the other cultivar despite receiving substantial insect visits. Instead, continuous access alone lowered overall fungal diversity without restructuring composition, which was more strongly structured by inter-annual variation than by pollinator access treatment. Profiling of the volatile organic compounds in florets revealed clear differences between cultivars, but different access treatment induced only minor changes in the volatile blends. Our findings establish that pollinator guilds shape sunflower nectar microbiota in a genotype-dependent manner. We propose that diurnal insect visits seed nectar with specialist taxa, but whether those specialists establish depends on nectar availability and composition.

microbiology↗

bioRxiv2026

A plant single nucleotide polymorphism impacts nectar sugar composition, microbial diversity and pollinator visits

Nectar is a hub for plant-pollinator interactions, yet gene-level causal links between plant genetic variation, pollinator foraging and nectar microbial assembly remain poorly resolved. Using near-isogenic lines, innovative field time-lapse monitoring of pollinator visits and long-read amplicon sequencing of nectar microbiota, we show that a natural single-nucleotide variant at a cell-wall invertase gene (HaCWINV2) controls sunflower nectar chemistry and influences both pollinators and microbes. Plants homozygous for a loss-of-function HaCWINV2 allele produce sucrose-rich nectar, resulting in fewer bee visits under field conditions, while bumblebee visitation remained unaffected. In pollinator-excluded flowers, invertase-deficient plants harboured greater fungal diversity and compositionally distinct communities, indicating that nectar sugar profiles act as ecological filters shaping the nectar microbiome. This loss-of-function allele was found rarely and only at the heterozygote state in wild sunflowers and was fixed in 35% of cultivated lines indicating a positive selection during domestication. Our findings establish a causal link between a single gene and nectar chemistry with cascading ecological effects in a plant-pollinator system, illustrating how subtle genetic changes scale up to alter nectar traits, microbial assembly and pollinator foraging behaviour.

genetics↗

bioRxiv2025

Genotype-Dependent Response to Water Deficit: Increases in Maize Cell Wall Digestibility Occurs Through Reducing Both p-Coumaric Acid and Lignification of the Rind

The compositional dynamics of the cell wall are influenced by drought, and it has been demonstrated that water deficit induces significant changes in its main components. Moreover, changes in cell wall concentration and distribution in response to water deficit affect maize degradability. This study presents a histological and biochemical analysis of thirteen maize inbred lines, evaluated over two years in Pobra de Brollon (Spain) and Mauguio (France) under contrasting water availability conditions. Our aim was to investigate the environmental and genotypic impacts on histological and biochemical profiles, to assess in vitro cell wall digestibility under water deficit, and to explore how these responses relate to changes in cell wall composition and structure. Overall, we observed greater concentrations of p-coumaric acid under control conditions, with significant decreases in stressed conditions at each location. Histologically, we found an increase in non-lignified tissues under water deficit conditions across all tissues and in both locations. In terms of in vitro cell wall digestibility (IVCWRD), significant increases were detected in response to water deficit. Additionally, genotype-dependent response patterns were evident, revealing two distinct behavioural groups. Notably, in plastic genotypes, increases in IVCWRD in response to water deficit were concomitant to reductions in p-coumaric acid content and a decrease in red-stained lignified tissues in the rind. This study emphasizes the complex, genotype-dependent responses to water deficit, underscoring the important roles of plasticity and stability in shaping the impact on maize cell wall digestibility; paving the way to breed for adapted genotypes to face climate changes. HighlightIncreased digestibility in response to water deficit is genotype-dependent and linked to reductions in p-coumaric acid content and lower lignification of the rind

physiology↗

bioRxiv2024

Cell wall digestibility outperforms ear in maintaining digestibility even under severe combined water and heat stress

CONTEXT OR PROBLEMForage maize is a central pillar of dairy cow feeding in France, directly influencing milk production. Drought significantly affects both maize yield and digestibility, which are both key parameters required for hybrid registration purposes. OBJECTIVE OR RESEARCH QUESTIONResearch on maize inbred lines has revealed droughts notable effect on dry matter and cell wall digestibilities due to changes in cell wall composition, directly impacting forage quality. No such studies have been performed on forage maize hybrids however, which are the main seed type used in the agricultural sector. In this paper, we aimed to understand the impact of water and heat stress on forage maize digestibility, and to uncover the factors controlling it. METHODSWe grew a range of modern forage maize hybrids for two years under four different controlled water stress modalities. These plants were agronomically, biochemically and histologically assayed, allowing us to perform a multiscale analysis to determine the traits responsible for variations in digestibility. RESULTSBy establishing a comprehensive heat and water stress index, we classified the environmental conditions. We demonstrated that under severe stress, ear production decreases significantly, but dry matter digestibility can be maintained through increased cell wall digestibility. This boost in cell wall digestibility was due to a reduction in p-hydroxycinnamic acid content and changes in lignin distribution, while lignin content and structure remained stable. The significant impact of lignin distribution on cell wall digestibility increased with the severity of the stress, reaching an extreme threshold where biochemical parameters solely account for digestibility variations. CONCLUSION AND IMPLICATIONSTo improve maize digestibility, it will be necessary to better understand how the reduction in carbon flux under stress affects p-hydroxycinnamic acid levels without greatly impacting lignin content. Finally, our work suggests that the inclusion of moderate stress conditions in future maize breeding programs will be necessary to better adapt forage maize hybrids to climate change.

plant biology↗

bioRxiv2018

Assessing the response of small RNA populations to allopolyploidy using resynthesized Brassica napus allotetraploids

Allopolyploidy, combining interspecific hybridization with whole genome duplication, has had significant impact on plant evolution. Its evolutionary success is related to the rapid and profound genome reorganizations that allow neo-allopolyploids to form and adapt. Nevertheless, how neo-allopolyploid genomes adapt to regulate their expression remains poorly understood. The hypothesis of a major role for small non-coding RNAs (sRNAs) in mediating the transcriptional response of neo-allopolyploid genomes has progressively emerged. Generally, 21-nt sRNAs mediate post-transcriptional gene silencing (PTGS) by mRNA cleavage whereas 24-nt sRNAs repress transcription (transcriptional gene silencing, TGS) through epigenetic modifications. Here, we characterize the global response of sRNAs to allopolyploidy in Brassica, using three independently resynthesized B. napus allotetraploids surveyed at two different generations in comparison with their diploid progenitors. Our results suggest an immediate but transient response of specific sRNA populations to allopolyploidy. These sRNA populations mainly target non-coding components of the genome but also target the transcriptional regulation of genes involved in response to stresses and in metabolism; this suggests a broad role in adapting to allopolyploidy. We finally identify the early accumulation of both 21- and 24-nt sRNAs involved in regulating the same targets, supporting a PTGS-to-TGS shift at the first stages of the neo-allopolyploid formation. We propose that reorganization of sRNA production is an early response to allopolyploidy in order to control the transcriptional reactivation of various non-coding elements and stress-related genes, thus ensuring genome stability during the first steps of neo-allopolyploid formation.

evolutionary biology↗