Experimental evolution of multicellularity [Evolution]

Experimental evolution of multicellularity [Evolution]: Multicellularity was one of the most significant innovations in the history of life, but its initial evolution remains poorly understood. Using experimental evolution, we show that key steps in this transition could have occurred quickly. We subjected the unicellular yeast Saccharomyces cerevisiae to an environment in which we expected multicellularity to be adaptive. We observed the rapid evolution of clustering genotypes that display a novel multicellular life history characterized by reproduction via multicellular propagules, a juvenile phase, and determinate growth. The multicellular clusters are uniclonal, minimizing within-cluster genetic conflicts of interest. Simple among-cell division of labor rapidly evolved. Early multicellular strains were composed of physiologically similar cells, but these subsequently evolved higher rates of programmed cell death (apoptosis), an adaptation that increases propagule production. These results show that key aspects of multicellular complexity, a subject of central importance to biology, can readily evolve from unicellular eukaryotes.

Transcriptional interpretation of the EGF receptor signaling gradient [Developmental Biology]

Transcriptional interpretation of the EGF receptor signaling gradient [Developmental Biology]: Epidermal growth factor receptor (EGFR) controls a wide range of developmental events, from body axes specification in insects to cardiac development in humans. During Drosophila oogenesis, a gradient of EGFR activation patterns the follicular epithelium. Multiple transcriptional targets of EGFR in this tissue have been identified, but their regulatory elements are essentially unknown. We report the regulatory elements of broad (br) and pipe (pip), two important targets of EGFR signaling in Drosophila oogenesis. br is expressed in a complex pattern that prefigures the formation of respiratory eggshell appendages. We found that this pattern is generated by dynamic activities of two regulatory elements, which display different responses to Pointed, Capicua, and Mirror, transcription factors involved in the EGFR-mediated gene expression. One of these elements is active in a pattern similar to pip, a gene repressed by EGFR and essential for establishing the dorsoventral polarity of the embryo. We demonstrate that this similarity of expression depends on a common sequence motif that binds Mirror in vitro and is essential for transcriptional repression in vivo.

Tissue-specific analysis of chromatin state identifies temporal signatures of enhancer activity during embryonic development

Tissue-specific analysis of chromatin state identifies temporal signatures of enhancer activity during embryonic development:

Tissue-specific analysis of chromatin state identifies temporal signatures of enhancer activity during embryonic development

Nature Genetics 44, 148 (2012).
doi:10.1038/ng.1064

Authors: Stefan Bonn, Robert P Zinzen, Charles Girardot, E Hilary Gustafson, Alexis Perez-Gonzalez, Nicolas Delhomme, Yad Ghavi-Helm, Bartek Wilczyński, Andrew Riddell & Eileen E M Furlong

Sex Pheromone Evolution Is Associated with Differential Regulation of the Same Desaturase Gene in Two Genera of Leafroller Moths

Sex Pheromone Evolution Is Associated with Differential Regulation of the Same Desaturase Gene in Two Genera of Leafroller Moths:

by Jérôme Albre, Marjorie A. Liénard, Tamara M. Sirey, Silvia Schmidt, Leah K. Tooman, Colm Carraher, David R. Greenwood, Christer Löfstedt, Richard D. Newcomb

Chemical signals are prevalent in sexual communication systems. Mate recognition has been extensively studied within the Lepidoptera, where the production and recognition of species-specific sex pheromone signals are typically the defining character. While the specific blend of compounds that makes up the sex pheromones of many species has been characterized, the molecular mechanisms underpinning the evolution of pheromone-based mate recognition systems remain largely unknown. We have focused on two sets of sibling species within the leafroller moth genera Ctenopseustis and Planotortrix that have rapidly evolved the use of distinct sex pheromone blends. The compounds within these blends differ almost exclusively in the relative position of double bonds that are introduced by desaturase enzymes. Of the six desaturase orthologs isolated from all four species, functional analyses in yeast and gene expression in pheromone glands implicate three in pheromone biosynthesis, two Δ9-desaturases, and a Δ10-desaturase, while the remaining three desaturases include a Δ6-desaturase, a terminal desaturase, and a non-functional desaturase. Comparative quantitative real-time PCR reveals that the Δ10-desaturase is differentially expressed in the pheromone glands of the two sets of sibling species, consistent with differences in the pheromone blend in both species pairs. In the pheromone glands of species that utilize (Z)-8-tetradecenyl acetate as sex pheromone component (Ctenopseustis obliquana and Planotortrix octo), the expression levels of the Δ10-desaturase are significantly higher than in the pheromone glands of their respective sibling species (C. herana and P. excessana). Our results demonstrate that interspecific sex pheromone differences are associated with differential regulation of the same desaturase gene in two genera of moths. We suggest that differential gene regulation among members of a multigene family may be an important mechanism of molecular innovation in sex pheromone evolution and speciation.

Stochastic Expression of the Interferon-β Gene

Stochastic Expression of the Interferon-β Gene:

by Mingwei Zhao, Jiangwen Zhang, Hemali Phatnani, Stefanie Scheu, Tom Maniatis

Virus infection of mammalian cells induces the production of high levels of type I interferons (IFNα and β), cytokines that orchestrate antiviral innate and adaptive immunity. Previous studies have shown that only a fraction of the infected cells produce IFN. However, the mechanisms responsible for this stochastic expression are poorly understood. Here we report an in depth analysis of IFN-expressing and non-expressing mouse cells infected with Sendai virus. Mouse embryonic fibroblasts in which an internal ribosome entry site/yellow fluorescent protein gene was inserted downstream from the endogenous IFNβ gene were used to distinguish between the two cell types, and they were isolated from each other using fluorescence-activated cell sorting methods. Analysis of the separated cells revealed that stochastic IFNβ expression is a consequence of cell-to-cell variability in the levels and/or activities of limiting components at every level of the virus induction process, ranging from viral replication and expression, to the sensing of viral RNA by host factors, to activation of the signaling pathway, to the levels of activated transcription factors. We propose that this highly complex stochastic IFNβ gene expression evolved to optimize both the level and distribution of type I IFNs in response to virus infection.

Gene Regulatory Logic for Reading the Sonic Hedgehog Signaling Gradient in the Vertebrate Neural Tube

Gene Regulatory Logic for Reading the Sonic Hedgehog Signaling Gradient in the Vertebrate Neural Tube: Nikolaos Balaskas, Ana Ribeiro, Jasmina Panovska, Eric Dessaud, Noriaki Sasai, Karen M. Page, James Briscoe, Vanessa Ribes. Secreted signals, known as morphogens, provide the positional information that organizes gene expression and cellular differentiation in many developing tissues. In the vertebrate neural tube, Son....

Extensive Promoter-Centered Chromatin Interactions Provide a Topological Basis for Transcription Regulation

Extensive Promoter-Centered Chromatin Interactions Provide a Topological Basis for Transcription Regulation: Guoliang Li, Xiaoan Ruan, Raymond K. Auerbach, Kuljeet Singh Sandhu, Meizhen Zheng, Ping Wang, Huay Mei Poh, Yufen Goh, Joanne Lim, Jingyao Zhang, Hui Shan Sim, Su Qin Peh, Fabianus Hendriyan Mulawadi, Chin Thing Ong, Yuriy L. Orlov, Shuzhen Hong, Zhizhuo Zhang, Steve Landt, Debasish Raha, Ghia Euskirchen, Chia-Lin Wei, Weihong Ge, Huaien Wang, Carrie Davis, Katherine I. Fisher-Aylor, Ali Mortazavi, Mark Gerstein, Thomas Gingeras, Barbara Wold, Yi Sun, Melissa J. Fullwood, Edwin Cheung, Edison Liu, Wing-Kin Sung, Michael Snyder, Yijun Ruan. Higher-order chromosomal organization for transcription regulation is poorly understood in eukaryotes. Using genome-wide Chromatin Interaction Analysis with Paired-End-Tag sequencing (ChIA-PET), w....