Deep Time Colloquium
Barthet, Michelle , Hilu, Khidir W. .
MatK: molecular evolution and functional constraints across green plants.
THE matK gene evolves at three times the rate of rbcL and atpB at the nucleotide level and six times that at the amino acid level. It has provided strong phylogenetic signals for resolving evolutionary relationships among plants at shallow and deep taxonomic levels. However, this high substitution rate, as well as the presence of indels, suggests relaxed evolutionary constraint on matK and potential instability in protein structure that may impact its function. MatK is proposed to function as a group II intron maturase in the chloroplast. This potentially essential function of MatK implies that evolutionary constraint must exist in some manner on this gene or its protein product. We propose that evolutionary constraint exists on MatK to maintain chemical properties of amino acid side chains, conserving its protein function. Analyses of amino acid side chain composition and variation for putative MatK protein sequences across green plants, as well as prediction of secondary structure from Oryza sativa, have demonstrated that both functional and structural constraints act at the protein level. Further, this study has identified three regions of functional or structural importance, suggested hydrophobic tendencies in this protein similar to other maturases, and supported MatK function as a putative group II intron maturase of the chloroplast. This work also provides a framework for examining molecular evolution beyond the nucleotide and amino acid sequence levels to determine the actual effect of substitution on the protein product, particularly in rapidly evolving genes. These results further support the utility of this gene in plant systematics.[c.e.:srb]
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1 - Virginia Tech, Biological Sciences, Blacksburg, Virginia, 24061, USA
Presentation Type: Symposium or Colloquium Presentation
Location: 206/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 11:30 AM