Biology subjects

Bresson, J.

Publications and source records attributed to Bresson, J..

5 recordsLinked to original sources

bioRxiv2024

Fis family members synergistically control the virulence of Legionella pneumophila

Legionella pneumophila virulence is controlled in a growth phase-dependent manner by a complex regulatory network involving several two-component systems, small regulatory RNAs and the translational CsrA regulator. Here, we address the additional role of Nucleoid-associated proteins (NAP) regulators in this network, by investigating the regulatory functions of the three Fis paralogs (Fis1, Fis2, Fis3), a unique feature among bacteria, in the infection cycle of L. pneumophila. Specifically, we show that deletion of fis1 has a major impact on L. pneumophila virulence, and that deletion of fis2 enhances the intensity of this phenotype. Consistently, RNA-seq analysis and reporter gene fusions demonstrate the predominant role of Fis1 in the regulation of many virulence-related genes, including those involved in the flagellum, pili biosynthesis, and Dot/Icm type 4 secretion machinery, as well as several genes encoding Dot/Icm effectors. Both Fis1 and Fis2 bind to AT-rich motifs upstream their target genes, but Fis1 with higher affinity than Fis2. Importantly, Fis1 and Fis2 would be capable of forming heterodimers that could bind with variable affinity to this AT-rich motif. It is also important to note that the three Fis proteins are not produced at the same time and in the same amounts. We therefore hypothesize that the duplication of fis genes in L. pneumophila is not simply a back-up system to compensate for potentially deleterious mutations in a fis gene, but rather a means to fine-tune the expression of targeted genes, particularly virulence genes. IMPORTANCEAppropriate control of virulence gene expression is crucial to the success of bacterial infection. Nucleoid-associated protein regulators, including Fis proteins, have been shown to participate in the virulence of several human pathogens. The importance of our discovery lies in the fact that L. pneumophila possesses three non-homologous Fis proteins instead of just one. We demonstrate that Fis1 and Fis2 are not functional duplicates of each other. On the contrary, Fis1 and Fis2 are synthesized neither simultaneously nor in equal amounts during the bacterial growth phase, and they cooperate to regulate virulence gene expression by targeting similar AT-rich motifs, albeit with distinct affinity, and by being capable of forming heterodimers. Taken together, our data suggest that the high conservation of fis gene duplication results from the need for fine-tuned control of Legionella virulence in response to its different environmental and human hosts, rather than from functional redundancy to circumvent deleterious fis mutations.

microbiology↗

bioRxiv2021

Into the range: a latitudinal gradient or a center-margins differentiation of ecological strategies in Arabidopsis thaliana?

Background and AimsDetermining within-species large-scale variation in phenotypic traits is central to elucidate the drivers of species ranges. Intraspecific comparisons offer the opportunity to understand how trade-offs and biogeographical history constrain adaptation to contrasted environmental conditions. Here we test whether functional traits, ecological strategies and phenotypic plasticity in response to abiotic stress vary along a latitudinal or a center-margins gradient within the native range of Arabidopsis thaliana. MethodsThe phenotypic outcomes of plant adaptation at the center and margins of its geographic range were experimentally examined in 30 accessions from southern, central and northern Europe. The variation of traits related to stress tolerance, resource use, colonization ability as well as survival and fecundity was determined in response to high temperature (34{degrees}C) or frost (- 6{degrees}C), in combination with response to water deficit. Key ResultsBoth evidence for a latitudinal and a center-margins differentiation was found. Traits related to the acquisitive/conservative strategy trade-off varied along a latitudinal gradient. Northern accessions presented a greater survival to stress than central and southern accessions. Traits related to a colonization-competition trade-off followed a center-margin differentiation. Central accessions presented a higher phenotypic plasticity and trait values associated with a higher colonization ability than northern and southern accessions which instead had a higher competition ability. ConclusionsIntraspecific phenotypic variation helps us understand how the distribution range has evolved in Arabidopsis thaliana, which is shaped both by climate and the population migratory history. We advocate to consider intraspecific trait variation in species range studies instead of species means only as classically done in macroecology.

ecology↗

bioRxiv2021

The genetic interaction of REVOLUTA and WRKY53 links plant development, senescence, and immune responses

In annual plants, tight coordination of successive developmental events is of primary importance to optimize performance under fluctuating environmental conditions. The recent finding of the genetic interaction of WRKY53, a key senescence-related gene with REVOLUTA, a master regulator of early leaf patterning, raises the question of how early and late developmental events are connected. Here, we investigated the developmental and metabolic consequences of an alteration of the REVOLUTA and WRKY53 gene expression, from seedling to fruiting. Our results show that REVOLUTA critically controls late developmental phases and reproduction while inversely WRKY53 determines vegetative growth at early developmental stages. We further show that these regulators of distinct developmental phases frequently, but not continuously, interact throughout ontogeny and demonstrated that their genetic interaction is mediated by the salicylic acid (SA). Moreover, we showed that REVOLUTA and WRKY53 are keys regulatory nodes of development and plant immunity thought their role in SA metabolic pathways, which also highlights the role of REV in pathogen defence. Together, our findings demonstrate how late and early developmental events are tightly intertwined by molecular hubs. These hubs interact with each other throughout ontogeny, and participate to the interplay between plant development and immunity.

plant biology↗

bioRxiv2019

Transcriptional natural variation at FLM induces synergistic pleiotropy in Arabidopsis thaliana

Investigating the evolution of complex phenotypes and the underlying molecular bases of their variation is critical to understand how organisms adapt to the environment. We used leaf growth as a model trait as it is highly integrative of internal and external cues and relies on functions at different levels of the plant organization. Applying classical quantitative genetics on a recombinant inbred line population derived from a Can-0 x Col-0 cross, we identified the MADS-box transcription factor FLOWERING LOCUS M (FLM) as a player of the phenotypic variation for leaf growth and colour. Interestingly, we showed that allelic variation at FLM modulates plant growth strategy along the leaf economics spectrum, a trade-off between resource acquisition and resource conservation observable across thousands of plant species. We demonstrated that the functional differences at FLM relies on a single intronic substitution, disturbing transcript splicing and leading to a low expression of the active FLM transcript. Using phenotypic and climatic data across Arabidopsis natural populations, our work shows how noncoding genetic variation of a single gene may be adaptive through synergistic pleiotropy.

plant biology↗

bioRxiv2017

Image-based methods for phenotyping growth dynamics and fitness in large plant populations

BackgroundThe model species Arabidopsis thaliana has extensive resources to investigate intraspecific trait variability and the genetic bases of ecologically relevant traits. However, the cost of equipment and software required for high-throughput phenotyping is often a bottleneck for large-scale studies, such as mutant screening or quantitative genetics analyses. Simple tools are needed for the measurement of fitness-related traits, like relative growth rate and fruit production, without investment in expensive infrastructures. Here, we describe methods that enable the estimation of biomass accumulation and fruit number from the analysis of rosette and inflorescence images taken with a regular camera.\n\nResultsWe developed two models to predict plant dry mass and fruit number from the parameters extracted with the analysis of rosette and inflorescence images. Predictive models were trained by sacrificing growing individuals for dry mass estimation, and manually measuring a fraction of individuals for fruit number at maturity. Using a cross-validation approach, we showed that quantitative parameters extracted from image analysis predicts more 90% of both plant dry mass and fruit number. When used on 451 natural accessions, the method allowed modelling growth dynamics, including relative growth rate, throughout the life cycle of various ecotypes. Estimated growth-related traits had high heritability (0.65 < H2 < 0.93), as well as estimated fruit number (H2 = 0.68). In addition, we validated the method for estimating fruit number with rev5, a mutant with increased flower abortion.\n\nConclusionsThe method we propose here is based on the automated computerization of plant images with ImageJ, and subsequent statistical modelling in R. It allows plant biologists to measure growth dynamics and fruit number in hundreds of individuals with simple computing steps that can be repeated and adjusted to a wide range of laboratory conditions. It is thus a flexible toolkit for the measurement of fitness-related traits in large plant populations.

bioinformatics↗