In “Molecular Phylogenetic Status of Microcentrum rhombifolium in the Family Tettigoniidae”, the authors of this paper focused on figuring out the molecular phylogenetic status of Microcentrum rhombifolium in the family Tettigoniidae. They did this by finding the partial sequence of the mitochondrial gene cytochrome oxidase subunit I (COI) of M. rhombifolium and comparing it to the other species in the family.

The family Tettigoniidae consists of about 6,000 species around the world. Included in the family are the katydids. The katydid we are focusing on today is the Microcentrum rhombifolium, or the “greater angle-wing katydid” of India. The paper focuses on its molecular phylogeny, or the DNA sequences of the organism, and uses them to analyze the organism’s relationship with the other species within the family. The specific DNA sequence found in this paper is the cytochrome oxidase subunit I. The cytochrome oxidase I gene is one that is mitochondrially encoded for cytochrome oxidase I, a protein that is the main subunit of the cytochrome oxidase complex of the electron transport chain.  

In order to analyze the COI subunit sequence for M. rhombifolium, the adult organisms were collected from the Calicut University in Malappuram, Kerala, India. After the genomic DNA was isolated from the thoracic legs of the organism, it was amplified using PCR for the mitochondrial COI gene. The PCR product was purified and sequenced from both ends using forward and reverse primers. Then, the forward and reverse sequences were assembled, the primer sequences were removed, and the sequence was analyzed. Finally, the divergence of COI sequence of M. rhombifolium from the other species of the family was calculated and placed in a phylogenetic tree.

Depicted is the phylogenetic status of M. rhombifolium among the 58 species of various genera of the family Tettigoniidae. (The text may not be clear in this picture. It is more clear on the original paper, which will be hyperlinked to this picture.)

Analyzing the COI subunit, it was found that the nearest relatives of genus Microcentrum were the genus Dioncomena and Monticolaria, Dioncomena ornate and Monticolaria meruensis being the nearest relatives to our species M. rhombifolium. Interestingly, Dioncomena and Microcentrum were found to come from a common ancestor. This makes sense as their evolutionary divergence between their COI sequences was one of the least, at 18.80%.

Since the genome is a fundamental property of all living organisms, it makes sense that some evolutionary trees have been constructed entirely from DNA sequences. This can be helpful in identifying organisms and their phylogenetic status. In the field of medicine, these evolutionary trees can be used to identify the origins of certain diseases caused by certain organisms in efforts to create a drug to combat the disease.

Overall, I found this paper very interesting! I have only ever seen phylogenetic trees based on external characteristics that organisms have in common. Therefore, I thought it was very unique how this study created a phylogenetic tree using entirely genomic DNA sequences. 

References:

Mashhoor, K., Akhilesh, V. P., Sebastian, C. D., Rosy, P. A., & Kottickal, L. V. (2012). Molecular Phylogenetic Status of Microcentrum rhombifolium in the Family Tettigoniidae. Developmental Microbiology and Molecular Biology, 3, 9-15.