IMEG

Institute of Molecular
Evolutionary Genetics

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

IMEG SEMINARS
Fall 2011

 

Previous IMEG Seminars and Abstracts:

Fall 2013

Spring 2013

Fall 2012

 

Spring 2012

Fall 2011

Fall 2010

 

Spring 2010
Fall 2009

Spring 2009

Fall 2008

Spring 2008

Fall 2007
Spring 2007
Fall 2006

Spring 2006
Fall 2005
Spring 2005

Fall 2004

Spring 2004

Fall 2003

Spring 2003
Fall 2002

Date

Speaker

 09/20/11

(Tues)

4:00 PM

100 Life Sci. Bldg.

HUCK INSTITUTES DINSTINGUISHED LECTURE

Speaker: Dr. Gunter Wagner - Yale University - Department of Ecology & EvolBiol

Title: Thinking outside the homeobox: evolution of gene regulation after the cis-trans controversy


 09/26/11

(Mon)

5:00PM

100 Life Sci Bldg.

MARKER LECTURE

Speaker: Dr. Jack Szostak - Harvard University - Department of Molecular Biology

Title: The Origin of Cellular Life

 

Abstract:

Dr. Szostak is an Investigator of the Howard Hughes Medical Institute, Professor of Genetics at Harvard Medical School, and the Alex Rich Distinguished Investigator in the Dept. of Molecular Biology and the Center for Computational and Integrative Biology at Massachusetts General Hospital. Dr. Szostak is a member of the National Academy of Sciences, and a Fellow of the New York Academy of Sciences, the American Academy of Arts and Sciences, and the American Association for the Advancement of Science.


Dr. Szostak’s early research was on the genetics and biochemistry of DNA recombination, which led to the double-strand-break repair model for meiotic recombination. At the same time Dr. Szostak made fundamental contributions to our understanding of telomere structure and function, and the role of telomere maintenance in preventing cellular senescence.  For this work Dr. Szostak shared, with Drs. Elizabeth Blackburn and Carol Greider, the 2006 Albert Lasker Basic Medical Research Award and the 2009 Nobel Prize in Physiology or Medicine.


In the 1990s Dr. Szostak and his colleagues developed in vitro selection as a tool for the isolation of functional RNA, DNA and protein molecules from large pools of random sequences.  His laboratory has used in vitro selection and directed evolution to isolate and characterize numerous nucleic acid sequences with specific ligand binding and catalytic properties. For this work, Dr. Szostak was awarded, along with Dr. Gerald Joyce, the 1994 National Academy of Sciences Award in Molecular Biology and the 1997 Sigrist Prize from the University of Bern.  In 2000, Dr. Szostak was awarded the Medal of the Genetics Society of America, and in 2008 Dr. Szostak received the H.P. Heineken Prize in Biophysics and Biochemistry.


Dr. Szostak’s current research interests are in the laboratory synthesis of self-replicating systems and the origin of life.

 09/27/11

(Tues)

4:00 PM

100 Life Sci. Bldg.

MARKER LECTURE

Speaker: Dr. Jack Szostak - Harvard University - Department of Molecular Biology

Title: Towards Self-Replicating Genetic Polymers

 10/19/11

(Wed)

12:10 PM

317 Mueller

Speaker: Dr. Stephen Schaeffer - Penn State University - Department of Biology

Title: Evolution of Genomic Rearrangements in Drosophila pseudoobscura

Abstract: The gene composition of chromosomes is conserved among Drosophila species, however, gene order varies widely among species.  An important mechanism for rearranging genes is chromosomal inversions that result from two double strand DNA breaks that are rejoined in reverse order.  Four general classes of models are used to explain how chromosomal inversions arise and are established in populations.  Drosophila pseudoobscura is a model for the study of mechanisms for the origin and spread of inversions.  This species has over 30 different gene arrangements that were generated by a series of overlapping inversions.  The frequencies of the different arrangements vary among populations and the major shifts in frequency are correlated with changes in the physiographic provinces in the southwestern United States.  My laboratory uses a combination of theoretical and experimental approaches to understand the genetic forces that modulate the frequencies of gene arrangements among populations.  This talk will summarize data from numerical and molecular population genetic analyses that evaluate hypotheses about the origin and maintenance of different gene arrangements.

 

References:

BHUTKAR, A., S. W. SCHAEFFER, S. RUSSO, M. XU, T. F. SMITH et al., 2008 Chromosomal rearrangement inferred from comparisons of twelve Drosophila genomes. Genetics 179: 1657-1680.

SCHAEFFER, S. W., M. J. BERNHARDT and W. W. ANDERSON, 2003 Evolutionary rearrangement of the amylase genomic regions between Drosophila melanogaster and Drosophila pseudoobscura. J. Hered. 94: 464-471.

WALLACE, A. G., D. DETWEILER and S. W. SCHAEFFER, 2011 Evolutionary History of the Third Chromosome Gene Arrangements of Drosophila pseudoobscura Inferred from Inversion Breakpoints. Mol. Biol. Evol. 28: 2219-2229.

 


11/01/11

(Tues)

4:00 PM

100 Life Sci. Bldg.

HUCK INSTITUTES DINSTINGUISHED LECTURE

Speaker: Dr. Robert Waterson – Washington University – Department of Genome Science

Title: Decoding Genomes: Lessons from C. elegans

 11/16/11

(Wed)

12:10 PM

317 Mueller

 

Speaker: Dr. Teh-hui Kao - Penn State University - Department of BMB

Title: A self/nonself recognition mechanism employing S-locus F-box proteins and S-RNase to prevent inbreeding in flowering plants

Abstract: Many flowering plants possess self-incompatibility (SI), which allows pistils to distinguish between self and non-self pollen, rejecting self-pollen to prevent inbreeding.  We are using Petunia inflata as a model to study the SI mechanism possessed by the Solanaceae.  Here, self/non-self recognition is controlled by the highly polymorphic S-locus.  The pistil recognizes pollen as self-pollen if the S-haplotype of pollen is also present in the pistil.  I will first discuss two polymorphic genes at the S-locus: the S-RNase gene (Ref. 1) which controls pistil specificity, and the S-locus F-box (SLF) gene, now named SLF1 (Ref. 2).   For several years after its identification, SLF1 was thought to be solely responsible for pollen specificity, and several models were developed based on this assumption (Ref. 3).  However, results inconsistent with this notion were subsequently obtained, which led to the recent finding that pollen specificity is controlled by multiple polymorphic SLF genes, SLF1, SLF2, SLF3, etc., at the S-locus (Ref. 4).  I will discuss a new model, named collaborative non-self recognition, which explains how pollen uses multiple SLF proteins to detoxify all non-self S-RNases during cross pollination, and why pollen allows self-S-RNase to exert its cytotoxicity during self-pollination.  I will close by discussing the implications of this new model for the evolution, operation and maintenance of SI possessed by the Solanaceae.

 

References:

1.  Lee H-S, Huang S, Kao T-h (1994). S proteins control rejection of incompatible pollen in Petunia inflata. Nature 367: 560-563

2.  Sijacic P, Wang X, Skirpan AL, Wang Y, Dowd PE, McCubbin AG, Huang S, Kao T-h (2004). Identification of the pollen determinant of S-RNase-mediated self-incompatibility. Nature 429: 302-305

3. Hua Z, Fields A, Kao T-h (2008). Biochemical models for S-RNase-based self-incompatibility. Mol Plant 1: 575-585

4.  Kubo K-I, Entani T, Takara A, Wang N, Fields AM, Hua Z, Toyoda M, Kawashima S-i, Ando T, Isogai A, Kao T-h, Takayama S (2010). Collaborative non-self recognition in S-RNase-based self-incompatibility. Science 330: 796-799

 

12/2011

(Wed)

12:10 PM

317 Mueller

Speaker: Sayaka Miura – Penn State University – Department of Biology

(Nei Lab)

Title: Is the larger number of miRNA genes in the teleost fish lineage than in tetrapod caused by genome duplication?

Abstract: The teleost fish lineage was separated from the tetrapod lineage about 400 million years ago, and it has been proposed that the teleost fish experienced genome duplication after separation from the tetrapod lineage. This genome duplication is supported by the studies of Hox gene, Fox gene, ParaHox gene, and KCNA gene families. However, inferring the occurrence of ancient genome duplication is very difficult, because duplicate genes changed by mutations and gene gains and losses. For this reason, the occurrence of genome duplication in the ancestral lineage of teleost fish is still controversial. MicroRNAs (miRNAs) are non-coding RNAs, and they are generally highly conserved. We therefore identified the miRNA genes that existed in the common ancestor of the teleost fish and tetrapod lineages and examined the number of these genes in the two descendant lineages. We examined the genomes of three teleost fish (zebrafish, Tetraodon, and medaka) and four tetrapod species (human, mouse, cow, and chicken). We identified ~100 ancestral miRNA homologous gene groups, and genes in 50-60% of these gene groups have experienced gene duplications. Therefore, we tested whether those duplications were caused by the genome duplication. We found that ~20 homologous gene groups have experienced more gene duplications in teleost fish than in tetrapods, and ~40% of gene duplications were found within duplicate segments that include other gene duplications. However, phylogenetic trees of miRNA genes in those duplicate segments indicated that only three duplicate segments were generated at the time of the genome duplication. Therefore, the larger number of miRNA genes in teleost fish than in tetrapods is suggestive of the genome duplication in teleost fish, but it is not conclusive.


References:

1. Amores A et al. 1998. Zebrafish hox clusters and vertebrate genome evolution. Science. 282:1711-1714.

2. Taylor JS, Braasch I, Frickey T, Meyer A, Van de Peer Y. 2003. Genome duplication, a trait shared by 22000 species of ray-finned fish. Genome Res. 13:382-390.