Biology subjects

Schmitz, G.

Publications and source records attributed to Schmitz, G..

4 recordsLinked to original sources

bioRxiv2018

Arabidopsis species deploy distinct strategies to cope with drought stress

O_LIBackground and Aims Water limitation is an important determinant of the distribution, abundance and diversity of plant species. Yet, little is known about how the response to limiting water supply changes among closely related plant species with distinct ecological preferences. Comparison of the model annual species A. thaliana to its close perennial relatives A. lyrata and A. halleri, can help disentangle the molecular and physiological changes contributing to tolerance and avoidance mechanisms, because these species must maintain tolerance and avoidance mechanisms to increase long-term survival, but they are exposed to different levels of water stress and competition in their natural habitat.\nC_LIO_LIMethods We conducted a dry-down experiment that mimics a period of missing precipitation. We quantified the covariation of progressive decrease in soil water content (SWC) with various physiological and morphological plant traits across a set of representative genotypes in Arabidopsis thaliana, A. lyrata and A. halleri. To quantify the degree of plant stress, transcriptome changes were also monitored.\nC_LIO_LIKey Results The analysis of trait co-variation demonstrates that the three species differ in the strategies they deploy to respond to drought stress. A. thaliana showed drought avoidance reaction but failed to survive wilting. A. lyrata efficiently combined avoidance and tolerance mechanisms. By contrast, A. halleri showed some degree of tolerance to wilting but it did not seem to protect itself from the stress imposed by drought. Transcriptome data collected just before plant wilting and after recovery corroborated the phenotypic analysis, with A. lyrata and A. halleri showing a stronger activation of recovery- and stress-related genes, respectively.\nC_LIO_LIConclusions We conclude that these three Arabidopsis species have evolved distinct strategies to face drought stress, and discuss the extent to which these strategic differences reflect their respective ecological priorities.\nC_LI

plant biology↗

bioRxiv2018

Robustness of Transposable Element regulation but no genomic shock observed in interspecific Arabidopsis hybrids

The merging of two divergent genomes in a hybrid is believed to trigger a \"genomic shock\", disrupting gene regulation and transposable element (TE) silencing. Here, we tested this expectation by comparing the pattern of expression of transposable elements in their native and hybrid genomic context. For this, we sequenced the transcriptome of the Arabidopsis thaliana genotype Col-0, the A. lyrata genotype MN47 and their F1 hybrid. Contrary to expectations, we observe that the level of TE expression in the hybrid is strongly correlated to levels in the parental species. We detect that at most 1.1% of expressed transposable elements belonging to two specific subfamilies change their expression level upon hybridization. Most of these changes, however, are of small magnitude. We observe that the few hybrid-specific modifications in TE expression are more likely to occur when TE insertions are close to genes. In addition, changes in epigenetic histone marks H3K9me2 and H3K27me3 following hybridization do not coincide with TEs with changed expression. Finally, we further examined TE expression in parents and hybrids exposed to severe dehydration stress. Despite the major reorganization of gene and TE expression by stress, we observe that hybridization does not lead to increased disorganization of TE expression in the hybrid. We conclude that TE expression is globally robust to hybridization and that the term \"genomic shock\" is no longerappropriate to describe the anticipated consequences of merging divergent genomes in a hybrid.

genomics↗

bioRxiv2017

Super-Resolution Ultrasound Bubble Tracking for Preclinical and Clinical Multiparametric Tumor Characterization

Super-resolution imaging methods promote tissue characterization beyond the spatial resolution limits of the devices and bridge the gap between histopathological analysis and non-invasive imaging. Here, we introduce Ultrasound Bubble Tracking (UBT) as an easily applicable and robust new tool to morphologically and functionally characterize fine vascular networks in tumors at super-resolution. In tumor-bearing mice and for the first time in patients, we demonstrate that within less than one minute scan time UBT can be realized using conventional preclinical and clinical ultrasound devices. In this context, next to highly detailed images of tumor microvascularization and the reliable quantification of relative blood volume and perfusion, UBT provides access to multiple new functional and morphological parameters that showed superior performance in discriminating tumors with different vascular phenotypes. Furthermore, our initial clinical results indicate that UBT is a highly translational technology with strong potential for the multiparametric characterization of tumors and the assessment of therapy response.

cancer biology↗

bioRxiv2017

Signature Of Co-Evolution Between Defense And Vegetative Lifespan Strategies In Arabidopsis thaliana

The selective impact of pathogen epidemics on host defenses can be strong but remains transient. By contrast, life-history shifts can durably and continuously modify the balance between costs and benefits of immunity, which arbitrates the evolution of host defenses. Their impact on the evolutionary dynamics of host immunity, however, has seldom been documented. Optimal investment into immunity is expected to decrease with shortening lifespan, because a shorter life decreases the probability to encounter pathogens or enemies. Here, we document that in natural populations of Arabidopsis thaliana, the expression levels of immunity genes correlate positively with flowering time, which in annual species is a proxy for lifespan. Using a novel genetic strategy based on bulk-segregants, we partitioned flowering time-dependent from - independent immunity genes and could demonstrate that this positive co-variation can be genetically separated. It is therefore not explained by the pleiotropic action of some major regulatory genes controlling both immunity and lifespan. Moreover, we find that immunity genes containing variants reported to impact fitness in natural field conditions are among the genes whose expression co-varies most strongly with flowering time. Taken together, these analyses reveal that natural selection has likely assorted alleles promoting lower expression of immunity genes with alleles that decrease the duration of vegetative lifespan in A. thaliana and vice versa. This is the first study documenting a pattern of variation consistent with the impact that selection on flowering time is predicted to have on diversity in host immunity.

evolutionary biology↗