Biology subjects

Brady, S.

Publications and source records attributed to Brady, S..

22 records · Page 2Linked to original sources

bioRxiv2019

Epistatic Transcription Factor Networks Differentially Modulate Arabidopsis Growth and Defense

Plants integrate internal and external signals to finely coordinate growth and defense allowing for maximal fitness within a complex environment. One common model for the relationship between growth and defense is a trade-off model in which there is a simple negative interaction between growth and defense theoretically driven by energy costs. However, there is a developing consensus that the coordination of growth and defense likely involves a more conditional and intricate connection. To explore how a transcription factor network may coordinate growth and defense, we used high-throughput phenotyping to measure growth and flowering in a set of single and pairwise mutants previously linked to the aliphatic glucosinolate defense pathway. Showing the link between growth and aliphatic glucosinolate defense, 17 of the 20 tested TFs significantly influence plant growth and/or flowering time. These effects were conditional upon the environment, age of the plant and more critically varied amongst the phenotypes when using the same genotype. The phenotypic effects of the TF mutants on SC GLS accumulation and on growth did not display a simple correlation, supporting the coordination model. We propose that large transcription factor networks create a system to integrate internal and external signals and separately modulate growth and the accumulation of the defensive aliphatic GLS.

plant biology↗

bioRxiv2019

A beneficial genomic rearrangement creates multiple versions of calcipressin in C. elegans

Gene duplication is a major source of genetic novelty and evolutionary adaptation, providing a molecular substrate that can generate biological complexity and diversity (Ohno 1967, Taylor and Raes 2004). Despite an abundance of genomic evidence from extant organisms suggesting the importance of gene duplication, consensus about how they arise and functionally diversify is lacking (Innan and Kondrashov 2010). In the process of studying the adaptation of laboratory strains of C. elegans to new food sources, we identified a recombinant inbred line (RIL) with higher relative fitness and hyperactive exploration behavior compared to either parental strain. Using bulk-segregant analysis and short-read resequencing, we identified a de novo beneficial, complex rearrangement of the rcan-1 gene, which we resolved into five new unique tandem inversion/duplications using Oxford Nanopore long-read sequencing. rcan-1 encodes an ortholog to human RCAN1/DSCR1, which has been implicated as a causal gene for Down syndrome (Fuentes, Genesca et al. 2000). The genomic rearrangement in rcan-1 causes two complete and two truncated versions of the rcan-1 coding region, with a variety of modified promoter and 3 regions, which ultimately reduce whole-body gene expression. This rearrangement does not phenocopy a loss-of-function allele, which indicates that the rearrangement was necessary for the observed fitness gains. Our results demonstrate that adaptation can occur through unexpectedly complex genetic changes that can simultaneously duplicate and diversify a gene, providing the molecular substrate for future evolutionary change.

evolutionary biology↗

bioRxiv2019

Transcriptional dynamics of bread wheat in response to nitrate and phosphate supply reveal functional divergence of genetic factors involved in nitrate and phosphate signaling

Nitrate (N) and phosphate (P) levels are sensed by plant cells and signaled via local and systemic signaling pathways to modulate plant growth and development. Understanding the genetic basis of these signaling mechanisms is key to future improvement of nutrient use efficiency. While major progress has been made in understanding N and P signaling pathways and their interaction in the model plant Arabidopsis, understanding of transcriptional responses to N and P in a major monocot crop wheat is lacking. Therefore, we investigated gene expression dynamics of wheat roots in response to N and/or P provision using RNA-Seq. We found that nitrate presence is the major trigger for most of the transcriptional response to occur within 24 h, however, we also identified a large array of synergistic transcriptional responses to concomitant supply of N and P. Through gene co-expression analysis, we identified gene co-expression modules prominent in nitrate signaling and metabolism in wheat. Importantly, we identified likely instances of functional divergence in major N-responsive transcription factors families HRS1/HHO and TGA of wheat from their rice/Arabidopsis homologues. Our work broadens the understanding of wheat N and P transcriptional responses and aids in prioritizing gene candidates for production of wheat varieties that are efficient in nitrogen usage.

plant biology↗

bioRxiv2018

Common loci underlie natural variation in diverse toxin responses

Phenotypic complexity is caused by the contributions of environmental factors and multiple genetic loci, interacting or acting independently. Studies of yeast and Arabidopsis found that the majority of natural variation across phenotypes is attributable to independent additive quantitative trait loci (QTL). Detected loci in these organisms explain most of the estimated heritable variation. By contrast, many heritable components underlying phenotypic variation in metazoan models remain undetected. Before the relative impacts of additive and interactive variance components on metazoan phenotypic variation can be dissected, high replication and precise phenotypic measurements are required to obtain sufficient statistical power to detect loci contributing to this missing heritability. Here, we used a panel of 296 recombinant inbred advanced intercross lines of Caenorhabditis elegans and a high-throughput fitness assay to detect loci underlying responses to 16 different toxins, including heavy metals, chemotherapeutic drugs, pesticides, and neuropharmaceuticals. Using linkage mapping, we identified 82 QTL that underlie variation in responses to these toxins and predicted the relative contributions of additive loci and genetic interactions across various growth parameters. Additionally, we identified three genomic regions that impact responses to multiple classes of toxins. These QTL hotspots could represent common factors impacting toxin responses. We went further to generate near-isogenic lines and chromosome-substitution strains and then experimentally validated these QTL hotspots, implicating additive and interactive loci that underlie toxin-response variation.

genetics↗