Project description:Leaf shape is a spectacularly diverse trait that influences various aspects of plant physiology, and is even correlated with crop yield and quality in multiple species. However, only a few genetic dissections of leaf shape have been accomplished at a species-wide level. Here, we perform an initial characterization of leaf shape variation in Ipomoea batatas, the sweetpotato, at multiple scales of analysis. We use a transcriptomic survey to identify gene expression changes associated with two commonly studied leaf shape traits--circularity and aspect ratio using 19 individuals (accession) of sweetpotato. We comprehensively describe the remarkable morphological diversity in leaf shape in sweetpotato, and identify 147 differentially regulated genes associated with circularity and aspect ratio, providing an initial set of hypotheses regarding the genetic basis of leaf shape in this species.
Project description:The observation that animal morphology tends to be conserved during the embryonic phylotypic period led to the proposition that embryogenesis diverges more extensively early and late than in the middle, known as the hourglass model. This pattern of conservation is thought to reflect a major constraint on the evolution of animal body plans. Despite a wealth of morphological data confirming that there is often remarkable divergence in the early and late embryos of species from the same phylum, it is not yet known to what extent gene expression evolution, which plays a central role in the elaboration of different animal forms, underpins the morphological hourglass. Here we address this question using species-specific microarrays designed from six sequenced Drosophila species. Although it is generally appreciated that gene expression divergence plays a key role in the evolution of morphological diversity, no studies to date have addressed the extent to which expression divergence underpins the hourglass pattern at the genome-wide level. We test the molecular basis of the hourglass model of developmental evolution using gene expression data from six Drosophila species with sequenced genomes (D. ananassae, D. melanogaster, D. persimilis, D. pseudoobscura, D. simulans, and D. virilis) thereby enabling unambiguous quantitative comparisons across orthologous genes for a set of species separated by up to 40 million years. Gene expression levels were measured for 3019 genes, known to be expressed during embryonic development from RNA in situ data, at 2 hour intervals for the majority of embryogenesis using a microarray time-course with three biological replicates per species and four species-specific probes per gene.
Project description:Neural crest (NC) is a vertebrate-specific embryonic progenitor cell population at the basis of important vertebrate features such as the craniofacial skeleton and pigmentation patterns. Despite the wide-ranging variation of NC-derived traits across vertebrates, the contribution of NC to species diversification remains underexplored. Here, leveraging the adaptive diversity of African Great Lakes’ cichlid species, we combined comparative transcriptomics and population genomics to investigate the evolution of the NC genetic programme in the context of their morphological divergence. Our analysis revealed substantial differences in transcriptional landscapes across somitogenesis, an embryonic period coinciding with NC development and migration. This included dozens of genes with described functions in the vertebrate NC gene regulatory network, several of which showed signatures of positive selection. Among candidates showing between-species expression divergence, we focused on teleost-specific paralogs of the NC-specifier sox10 (sox10a and sox10b) as prime candidates to influence NC development. These genes, expressed in NC cells, displayed remarkable spatio-temporal variation in cichlids, suggesting their contribution to inter-specific morphological differences, such as craniofacial structures and pigmentation. Finally, through CRISPR/Cas9 mutagenesis, we demonstrated the functional divergence between cichlid sox10 paralogs, with the acquisition of a novel skeletogenic function by sox10a. When compared to teleost models zebrafish and medaka, our findings reveal that sox10 duplication, although retained in most teleost lineages, had variable functional fates across their phylogeny. Altogether, our study suggests that NC-related processes – particularly those controlled by sox10s – are involved in generating morphological diversification between species and lays the groundwork for further investigations into the mechanisms underpinning vertebrate NC diversification.
Project description:Iron is limiting in the environment, bacteria respond to this deprivation by activating genes required for bacterial iron homeostasis. Transcriptional regulation in response to iron in Gram-negative bacteria is largely mediated by the ferric uptake regulator protein Fur, which in the presence of iron binds to a specific sequence in the promoter regions of genes under its control and acts as a repressor. Here we describe comparative global gene expression analysis using DNA microarray based on the whole genome sequence of the magnetotactic bacterium Magnetospirillum magneticum AMB-1 was conducted between wild type strain and a non-magnetic NMA61 mutant strain, generated by mini-Tn5 transposon mutagenesis which is incapable of assimilating iron to cytoplasm. No induction of the fur genes in NMA61 mutant strain was considered to be due to low intracellular iron concentration. In the iron-replete condition, among 4492 genes, 434 genes were down-regulated and 527 genes were up-regulated in the wild type strain. Among 434 genes down-regulated, 299 genes were not down-regulated in NMA61 mutant strain, indicating these genes are candidates of Fur-regulated. Keywords: Iron, magnetotactic bacteria
Project description:Gene-expression divergence between species shapes morphological evolution, but the molecular basis is largely unknown. Here we show cis- and trans-regulatory elements and chromatin modifications on gene-expression diversity in genetically tractable Arabidopsis allotetraploids. In Arabidopsis thaliana and Arabidopsis arenosa, both cis and trans with predominant cis-regulatory effects mediate gene-expression divergence. The majority of genes with both cis- and trans-effects are subjected to compensating interactions and stabilizing selection. Interestingly, chromatin modifications correlate with cis - and trans -regulation. In F1 allotetraploids, Arabidopsis arenosa trans factors predominately affect allelic expression divergence. Arabidopsis arenosa trans factors tend to upregulate Arabidopsis thaliana alleles, whereas Arabidopsis thaliana trans factors up- or down-regulate Arabidopsis arenosa alleles. In resynthesized and natural allotetraploids, trans effects drive expression of both homoeologous loci into the same direction. We provide evidence for natural selection and chromatin regulation in shaping gene-expression diversity during plant evolution and speciation. Examination of gene expression in 5 tetraploid Arabidopsis using mRNA-seq