Evolution of Development and Physiology
Shakirov, Eugene V. , Song, Xiangyu , Zanis, Michael , Croy, Johnny , Wuttke, Debbie , Shippen, Dorothy E. .
Evolution of POT genes in plants.
Telomeres are nucleoprotein complexes that distinguish the natural ends of chromosomes from damage-induced double-strand DNA breaks and help overcome the end-replication problem. Telomere architecture is well-conserved across evolution. In most plants, telomeric DNA consists of TTTAGGG repeats and is associated with sequence-specific DNA binding proteins, including Protection of Telomeres 1 (POT1). Although most organisms have only a single POT1 gene, Arabidopsis thaliana encodes two POT1-like genes. We have shown that AtPOT1a and AtPOT1b proteins are functionally non-redundant. AtPOT1a serves as a positive regulator of telomere length, acting as a component of the telomerase enzyme. In contrast, AtPOT1b functions in chromosome end protection. To explore the evolution of POT genes in plants, we obtained POT coding regions from over thirty organisms within the plant kingdom, ranging from green algae to the flowering plants. The presence of two POT genes appears to be a rare event: only two examples of such gene duplication events were detected. One POT gene duplication occurred in the family of Grasses, and the second in members of the Brassicaceae family. Members of the Brassicaceae POT lineage display an extraordinary rapid rate of amino acid change. Interestingly, AtPOT1a appears to be under greater evolutionary pressure than AtPOT1b. Our analysis suggests evidence for positive selection for AtPOT1a, with several residues located in an evolutionarily conserved alpha-helix of the DNA-binding domain. We are currently testing the functional relevance of these changes using a genetic complementation approach. Our findings suggest emerging neo-functionalization of AtPOT1a as a telomerase-associated telomere length regulator.
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1 - Texas A&M University, Biochemistry and Biophysics, 2128 tamu, College Station, TX, 77843-2128, USA
2 - Purdue University, Botany and Plant Pathology
3 - University of Colorado, Boulder, Chemistry and Biochemistry
4 - University of Colorado-Boulder, Chemistry and Biochemistry
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM