Barthet, Michelle , Hilu, Khidir W. .
matK, A Pseudogene or Not?.
The matK gene resides within the group II intron of trnK in the plastid genome of most land plants and Charaphyceae (green algae). This gene is approximately 1500 bp in length, corresponding to 500 amino acids. Sequence analysis identified highly variable regions in matK and at least one highly conserved region with homology to mitochondrial group II intron maturases. The substitution rate of the matK K gene was found to be up to three times higher than that of rbcL, denoting matK as a rapidly evolving gene. matK is also a signal rich gene. The molecular information contained within this single gene has produced phylogenies as robust as those achieved with five to eleven other genes combined. However, the high substitution rate, frame-shift mutations, and premature stop codons have led some to hypothesize that matK is a pseudogene. As a pseudogene, the matK DNA sequence would accumulate random mutations as junk DNA. Consequently, this gene would be considered less reliable for plant molecular phylogenetics. Pseudogenes can be described as copied genes that lack transcription or are unable to form a functional protein. We used the methods of RT-PCR and northern blot analysis to address the matK pseudogene hypothesis. We demonstrated that matK produces an RNA transcript in several taxa throughout the plant kingdom, supporting its functionality. Furthermore, we characterized aspects of this transcript including time of maximum transcription, approximate transcript length, and polyadenylation. This study strongly refutes the hypothesis that matK is a pseudogene and supports its function in the chloroplast genome. Thus,matK remains as a valuable gene in plant systematics.
1 - Virginia Polytechnic Institute and State University, Department of Biology, Blacksburg, Virginia, 24061, USA
Presentation Type: Paper
Location: Peruvian (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 1:15 PM