Biology subjects

Sawers, R. J. H.

Publications and source records attributed to Sawers, R. J. H..

3 recordsLinked to original sources

bioRxiv2018

Adaptive phenotypic divergence in teosinte differs across biotic contexts

Climate is a powerful force shaping adaptation within species, often creating dramatic phenotypic clines. Yet adaptation to climate does not occur in a vacuum: species interactions filter the fitness consequences of both climatic and phenotypic variation. In other words, the translation of genotype to phenotype may be altered by biotic context, influencing the variation upon which climatic selection can act. We investigate the role of such interactions in changing the phenotypes on which selection acts using ten populations of an annual grass species (teosinte: Zea mays ssp. mexicana) sourced from along an elevational gradient, along with rhizosphere biota sourced from three of those populations. We grow teosinte families in a half-sibling design in separate biota treatments to first test whether the divergence we see among traits in teosinte populations exceeds what we would expect from genetic drift and then whether the source of rhizosphere biota affects the expression of divergent traits. We also assay the influence of these three rhizosphere biotas on contemporary additive genetic variation in teosinte traits across populations. We find that expression of most measured traits in teosinte is altered by rhizosphere biota, as well as the degree of variance and covariance among traits involved in root mass and flowering time. As a number of these traits are also found to underlie adaptive divergence across habitats, our data suggest that biota influence the expression of traits underlying local adaptation. Together, our results suggest that changes in trait expression and covariance elicited by interactor communities in root mass and flowering time may have played a historical role in local adaption of teosinte to environments, and that they would play a contemporary role in responses to changing selection pressures.

evolutionary biology↗

bioRxiv2017

Allele specific expression analysis identifies regulatory variation associated with stress-related genes in the Mexican highland maize landrace Palomero Toluqueno

BackgroundGene regulatory variation has been proposed to play an important role in the adaptation of plants to environmental stress. In the central highlands of Mexico, farmer selection has generated a unique group of maize landraces adapted the challenges of the highland niche. In this study, gene expression in Mexican highland maize and a reference maize breeding line were compared to identify evidence of regulatory variation in stress-related genes. It was hypothesised that local adaptation in Mexican highland maize would be associated with a transcriptional signature observable even under benign conditions.\n\nMethodsAllele specific expression analysis was performed using the seedling-leaf transcriptome of an F1 individual generated from the cross between the highland adapted Mexican landrace Palomero Toluqueno and the reference line B73, grown under benign conditions. Results were compared with a published dataset describing the transcriptional response of B73 seedlings to cold, heat, salt and UV treatments.\n\nResultsA total of 2386 genes were identified to show allele specific expression. Of these, 277 showed an expression difference between Palomero Toluqueno and B73 alleles that mirrored the response of B73 cold, heat, salt and/or UV treatments, and, as such, were considered to display a constitutive stress response. Constitutive stress response candidates included genes associated with plant hormone signaling and a number of transcription factors. Construction of a gene co-expression network revealed further signaling and stress-related genes to be among the potential targets of the transcription factors candidates.\n\nDiscussionConstitutive activation of responses may represent the best strategy when stresses are severe but predictable. Expression differences observed here between PT and B73 alleles indicate the presence of cis-acting regulatory variation linked to stress-related genes in PT. Considered alongside gene annotation and population data, allele specific expression analysis of plants grown under benign conditions provides an attractive strategy to identify functional variation potentially linked to local adaptation.

plant biology↗

bioRxiv2016

Identification of the maize Mediator CDK8 module, and Dissociation insertional mutagenesis of ZmMed12a

Mediator is a conserved transcriptional co-activator that links transcription factors bound at enhancer elements to RNA Polymerase II. Mediator-RNA Polymerase II interactions can be sterically hindered by the Cyclin Dependent Kinase 8 (CDK8) module, a submodule of Mediator that acts to repress transcription in response to discrete cellular and environmental cues. The CDK8 module is conserved in all eukaryotes and consists of 4 proteins: CDK8, CYCLIN C (CYCC), MED12, and MED13. In this study, we have characterized the CDK8 module of Mediator in maize. The maize genome contains single copy genes for Cdk8, CycC, and Med13, and two genes for Med12. Analysis of expression data for the CDK8 module demonstrated that all five genes are broadly expressed in maize tissues, with ZmMed12a, ZmMed12b, and ZmMed13 exhibiting similar expression patterns. We performed a Dissociation (Ds) insertional mutagenesis, recovering two independent insertions in the ZmMed12a gene. One of these Ds insertions results in a truncation of the ZmMed12a transcript. Our molecular characterization of the maize CDK8 module, as well as transposon tagging of ZmMed12a, establish the basis for molecular and functional studies of these important transcriptional regulators in Zea mays.

plant biology↗