A. Bruce Cahoon

Current Research Interests

 I am currently focused on two broad interests:  organelle gene expression and plant tissue culture

 

Organelle Gene Expression

 Chloroplasts and mitochondria are semi-autonomous organelles that were incorporated into pre-eukaryotic cells through a process called endosymbiosis.  They have circular chromosomes with genes that are organized and expressed in ways that are unique in the biological world. 

 Gene expression is a two step process often called the central dogma of biology. One interesting aspect of this process in organelles is the variety of post-transcriptional processing events that do not resemble anything you learned about mRNA modifications in your basic biology or genetics courses.  These include trans-splicing, RNA editing, odd poly-cistronic gene groups, transcript separation, poly-A degradation signaling, and others both discovered and un-discovered.

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Members of my lab and collaborators recently published a survey of all the transcripts produced by the tobacco mitochondrial genome (Grimes et al 2014).  We initially asked the questions, “Why does the tobacco mitochondrial genome have so many uncharacterized open reading frames?  And  Are any of them transcribed and translated?”

 

We learned that some of them are transcribed and some may even be translated into protein.

 We also asked, “How many nucleotides are edited in all the RNAs?” and was surprised at the total number, 635, and that 73 of these were in non-coding regions.

 The result of this study is two new questions regarding RNA editing -  “Why are sites outside of coding regions edited?”  and much more broadly “Are there any evolutionary patterns within the botanical kingdom regarding these edit sites?”  We are designing experiments and will hopefully have some answers in the coming months/years.

 

Another transcriptome and RNA processing study is nearly completed for the dinoflagellate Karenia brevis, which is an environmentally important alga that causes red tide.  

 

This project was begun with the simple question, “Can we identify the chloroplast genes of the non-model alga, K. brevis using the sequenced transcriptome?” ; “Can we determine the genome morphology from the transcriptome?” ; and “Is it possible to infer processing events from the transcriptome?”

 

So far, more than 50 K. brevis chloroplast transcripts have been identified and several interesting processing events have been characterized.

 

 

Plant Tissue Culture

 Plant tissue culture is a tool or method used to propagate plant tissues, organs, or whole plants.

 

I have used culture techniques for embryo rescue, organogenesis, and embryogenesis, as needed, for the completion of experiments over the last 20+ years.  I have also taught tissue culture as part of a course in plant biotechnology. 

 

Recently, a collaboration with the Tennessee Center for Botanical Medicine Research inspired the culture of plants used in traditional herbology, including American ginseng (Panax quinquefolius).  My lab is currently attempting to answer the question, “What is the best way to cultivate ginseng on a commercial scale using micropropagation techniques?”