The footprint of polygenic adaptation on stress-responsive cis-regulatory divergence in the Arabidopsis genus
ABSTRACT: We generated F1 hybrids of each of the sister species A. halleri and A. lyrata with their outgroup relative of A. thaliana and monitored allele-specific levels of expression in standard growth conditions, in response to dehydration or cold exposure. This data allowed us to map the genome-wide distribution of cis-regulatory mutations active in three distinct environments reflecting divergent adaptations of the two species. Because the sister species were both crossed to an outgroup species, it was possible to assign a phylogenetic origin to cis-acting mutations. Cis-acting mutations observed in only one of the two hybrids were likely to be derived, whereas those observed in both hybrids either predate predated the split between the two species or arose along the A. thaliana lineage. By contrasting the distribution of cis-regulatory mutations derived in the A. halleri to those derived on the A. lyrata lineage, we could establish relative rates of cis-acting evolution across polygenic molecular functions and detect lineage-specific polygenic adaptation to environmental challenges. A.thalianaxA.lyrata under cold, dehydration and standard conditions, 3 biological replicates; A.thalianaxA.halleri under cold, dehydration and standard conditions, 3 biological replicates; toal 18 RNA-seq samples
Project description:We compared the expression between inter-specific hybrids (A. thaliana-A. lyrata, A. thaliana-A. halleri) and mid parent values of their parental lines. Mature leaves in A. thaliana (Col), A. lyrata ssp. lyrata, A. halleri ssp. gemmifera and interspecific hybrid between A. thaliana and A. lyrata and between A. thaliana and A. halleri
Project description:We compared the expression between inter-specific hybrids (A. thaliana-A. lyrata, A. thaliana-A. halleri) and mid parent values of their parental lines. Overall design: Mature leaves in A. thaliana (Col), A. lyrata ssp. lyrata, A. halleri ssp. gemmifera and interspecific hybrid between A. thaliana and A. lyrata and between A. thaliana and A. halleri
Project description:Gene copy number variation (CNV) is a form of genetic polymorphism that contributes significantly to genome size and function but remains poorly characterized due to technological limitations. Inter-specific comparisons of CNVs in recently diverged plant species are crucial to uncover selection patterns underlying adaptation of a species to stressful environments. Especially given that gene amplifications have long been implicated in emergence of species-specific traits, we conducted a genome-wide survey to identify species-specific gene copy number expansions and deletions in the model extremophile species - Arabidopsis halleri that has diverged in evolutionarily recent time from Arabidopsis thaliana. Cross-species cDNA array based comparative genomic hybridization was employed to compare and identify gene copy number variation in the two sister-species - the metallophyte Arabidopsis halleri and non-metallophyte Arabidopsis lyrata, both relative to Arabidopsis thaliana. We uncovered an unprecedented level of gene copy number polymorphism in Arabidopsis halleri, with a species-specific enrichment of metal homeostasis function in the genes found to be copy number expanded, thus indicating CNV as a mechanism that underlies the key physiological trait of metal hyperaccumulation and hypetolerance in A. halleri. Overall design: A total of 6 gDNA samples were hybridized to Affymetrix cDNA microarrays, two biological replicates for each of the three Arabidopsis species.
Project description:We analyzed allele-specific expression (ASE) in leaf and floral tissues of F1 interspecific hybrids generated between the two closely related species of Arabidopsis thaliana and Arabidopsis lyrata with a whole-genome SNP tiling array (AtSNPtile1). 24 sampes, 12 DNA samples from parents and hybrids, 12 RNA sample from leaf and flowers of hybrids
Project description:Self-pollen rejection in the Brassicaceae is determined by the diploid genotype of the pollen-producing plant, and it has long been known that the alleles show a dominance hierarchy. How this hierarchy is controlled and evolves has been a classical puzzle since the pre-molecular days of genetics. Here, we uncover the system of at least 17 small RNA (sRNA) producing loci and their multiple target sites that collectively control the dominance hierarchy among alleles of a self-incompatible Arabidopsis species. Our results demonstrate that natural selection shapes a dynamic repertoire of sRNA/targets interactions by jointly acting on sRNA genes, their processing precision and their target sites. It is remarkable that a single gene can evolve such a complex system of regulation among its own alleles. Sequencing of small RNAs from A. halleri floral buds, with this single exception (Al14, from A. lyrata).
Project description:Arabidopsis thaliana and Arabidopsis lyrata are two closely related Brassicaceae species, which are used as models for plant comparative biology. They differ by lifestyle, predominant mating strategy, ecological niches and genome organization. In order to explore molecular basis of specific traits, we performed RNA-sequencing of vegetative rosettes from both species. Additionally, we sequenced apical meristems and inflorescences of A. lyrata that allow for intra-specific transcriptome comparison in several major developmental stages. Arabidopsis lyrata and Arabidopsis thaliana aerial tissues were collected from mock treated plants, total RNA isolated and poly-A RNA populations sequenced
Project description:New shoot growth from underground adventitious buds of leafy spurge is critical for survival of this invasive perennial weed after episodes of severe abiotic stress. Because global climate change is expected to increase abiotic stress, such as dehydration, objectives of this study include examining the impact that dehydration stress has on molecular mechanisms associated with vegetative reproduction. Greenhouse plants were exposed to mild- (3-day), intermediate- (7-day), severe- (14-day) and extended- (21-day) dehydration treatments, prior to decapitation of aerial tissue and rehydration of soil to induce new vegetative shoot growth. Compared to well-watered control plants, mild-dehydration accelerated new vegetative shoot growth but intermediate- and severe-dehydration treatments both delayed and reduced shoot growth, and 21-day dehydration treatment inhibited initiation of new vegetative shoots and was considered a lethal treatment. Overall, transcriptome profiles revealed that 2109 genes were differentially-expressed (P<0.05) in crown buds in response to the various dehydration treatments. Sub-network enrichment analyses identified central hubs of over-represented genes involved in processes such as hormone responses and signaling (e.g., ABA, auxin, ethylene, GA, and JA), response to abiotic stress (DREB1A/2A) and light (PIF3), phosphorylation (CLV1, MPK3/4/6, SOS2), gene silencing (miRNA156/172a), circadian regulation (CRY2, LHY, PHYA/B), and flowering (AGL8/20, AP2, FLC). Further, results from this and previous studies highlight HY5, MAF3, MYB-like/RVE1 and RD22 as molecular markers for endodormancy in crown buds of leafy spurge. Early response to dehydration also highlighted involvement of upstream ethylene and jasmonate signaling, whereas longer-term dehydration impacted ABA signaling. The identification of conserved ABRE- and MYC-consensus, cis-acting elements in the promoter of a leafy spurge gene similar to Arabidopsis MYB-like/RVE1 (AT5G17300) implicates a potential role for ABA signaling in its dehydration-induced expression. Response of these molecular mechanisms to dehydration-stress provides insights on the ability of invasive perennial weeds to adapt and survive under harsh environments, which provide new insights for addressing future management practices. Changes in transcript abundance for underground adventitious buds of leafy spurge which were exposed various levels of dehydration stress (Day-3, -7, -14, -16, -21) are analysed relative to controls (Day-0).
Project description:Arabidopsis thaliana and Arabidopsis lyrata are two closely related Brassicaceae species, which are used as models for plant comparative biology. They differ by lifestyle, predominant mating strategy, ecological niches and genome organization. To identify heat stress induced genes, we performed RNA-sequencing of rosette leaves from mock-treated, heat-stressed and heat-stressed-recoved plants of both species. Analysis of genetic element transcriptional changes in response to 6 hours of 37°C heat stress and 48 hours of recovery in Arabidopsis thaliana Col-0 and Arabidopsis lyrata MN47.
Project description:Deep sequencing of the 5' ends of uncapped, polyA-enriched mRNA from two biological replicate samples from Arabidopsis thaliana inflorescences, as well as two biological replicates of Arabidopsis lyrata inflorescences. These data were used to experimentally identify sliced microRNA targets from the two species. Two biological replicate samples of the 5' ends of uncapped, polyA+ RNAs from both A. thaliana and A. lyrata
Project description:Changes in gene regulation rapidly accumulate between species and may contribute to reproductive isolation through misexpression of genes in interspecific hybrids. Hybrid misexpression, defined by expression levels outside the range of both parental species, is thought to be a result of cis- and trans-acting regulatory changes that interact in the hybrid, or arise from changes in the relative abundance of various tissues or cell types due to defects in developmental. Here, we show that misexpressed genes in a sterile interspecific Saccharomyces yeast hybrid result from a heterochronic shift in the timing of the normal meiotic gene expression program. By tracking nuclear divisions, we find that S. cerevisiae initiates meiosis earlier than its closest known relative, S. paradoxus, yet both species complete meiosis at the same time. Although the hybrid up- and down-regulates genes in a similar manner to both parents, the hybrid meiotic program occurs earlier than both parents. The timing shift results in a heterochronic pattern of misexpression throughout meiosis I and the beginning of meiosis II. Coincident with the timing of misexpression, we find an increase in the relative abundance of opposing cis and trans-acting changes and compensatory changes, as well as a transition from predominantly trans-acting to cis-acting expression divergence over the course of meiosis. However, misexpression does not appear to be a direct consequence of cis- and trans-acting regulatory divergence. Our results demonstrate that hybrid misexpression in yeast results from a heterochronic shift in the meiotic gene expression program. We analyzed three biological replicates of the parental yeast strains, S. cerevisiae and S. paradoxus, and four replicates of their hybrid over four developmental time points. Two hybrid replicates contain MATa from S. cerevisiae and MATalpha from S. paradoxus. The other two hybrid replicates are reciprocal crosses. The developmental time points are T0, which serves as a control, and is the moment cells enter sporulation media. M1 is the beginning of meiosis I. M1/M2 is the overlap of the end of meiosis I and the beginning of meiosis II. M2 is the end of meiosis II.