[Seminars] PSB event reminder

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Calendar Name: seminars
Scheduled for: Thursday, January 24 2013, 11:00 - 12:30
Event text:    Dr Steven Maere
	       
	       VIB, Dept. of Plant Systems Biology
	       Ghent University
	       
	       Gent
	       BELGIUM
Details:       “Innovation through gen(om)e duplication” 
	       
	       ABSTRACT
	       Gene and genome duplications are believed to facilitate
	       evolutionary innovation. However, the mechanisms shaping
	       the fate of duplicated genes remain heavily debated
	       because the molecular processes and evolutionary forces
	       involved are difficult to reconstruct. The first part of
	       the talk will focus on the MALS gene family, a large
	       family of fungal glucosidase genes with members
	       generally having activity on only one of two broad
	       substrate classes. We reconstructed several key
	       ancestral enzymes and show that the very first
	       preduplication enzyme was primarily active on
	       maltose-like substrates, but had trace activity for
	       isomaltose-like sugars. Structural analysis and activity
	       measurements on resurrected and present-day enzymes
	       suggest that both activities cannot be fully optimized
	       in a single enzyme. However, gene duplications
	       repeatedly spawned daughter genes in which mutations
	       optimized either isomaltase or maltase activity.
	       Interestingly, similar shifts in enzyme activity were
	       reached multiple times via different evolutionary
	       routes. Together, our results provide a detailed picture
	       of the molecular mechanisms that drove divergence and
	       innovation in the MALS gene family. In the second part
	       of the talk, I will discuss a framework we developed for
	       simulating the evolution of small biological systems in
	       silico. The genotype-phenotype map (GPM) of any
	       molecular system results from a highly multilayered
	       information processing cascade, in which gene regulatory
	       networks (GRNs) play a crucial role. Several simplifying
	       mathematical representations of GPMs have been developed
	       in the past. However, these representations generally
	       lack biological realism in the genotypic encoding of the
	       structure and parameters of GRNs. To study GPMs in
	       mechanistic detail, we have developed a sequence-based
	       dynamical modeling framework built upon biochemical
	       first principles. As a proof of concept, we focus on
	       genomes coding for small GRNs displaying oscillatory
	       expression phenotypes. We show that genome duplication
	       drastically impacts the navigability of the fitness
	       landscape and the accessibility of novel phenotypes.

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