UMBI’s Dr. Tsvetan R. Bachvaroff and Dr. Allen R. Place have provided a glimpse of the dinoflagellate genome that reveals a number of novel features. These findings are published in the August 2008 issue of PLoS one.

Dinoflagellates consist of a large group of mostly single celled, nucleated organisms that are abundant food sources for larger organisms in oceans, estuaries and lakes. Some dinoflagellates are associated with destructive blooms associated with environmental degradation.

Dr. Tsvetan R. Bachvaroff (left) and Dr. Allen R. Place

This first glimpse of the dinoflagellate genome—the genetic material of the organism—indicates a number of unusual features. First, the genome is unusually large—about 20 times larger than the human genome. Second, highly expressed genes appear to be present in large numbers of copies that are found in tandem arrays. Third, several of the genes are subject to a novel pattern of splicing when they are expressed.

In most nucleated organisms, segments of RNA transcribed from one single gene can be spliced together to create several new patterns, which allows one gene to be expressed as several distinct protein sequences. But in the dinoflagellates, a segment of a specific RNA-- called the spliced leader RNA or SL-RNA-- is added to the start of most of the protein-coding RNAs. This process, called trans-splicing--which is found in other organisms like some parasites, nematodes and rotifers--allows for novel ways to control the expression of the genes.

An intriguing feature of dinoflagellates is that they appear to be especially susceptible to a process known as endosymbiosis—an evolutionary process in which a microorganism is captured by a larger cell, and actually becomes part of a new organism that fuses both cells into a larger functional whole. In order for this to take place, some of the genes of the microorganism are incorporated into the nucleus of the larger cell. The authors suggest that the novel patterns observed in the genome may make the dinoflagellates unusually susceptible to incorporating microorganisms and their genetic material.

These early studies of the dinoflagellate genome indicate that these unusual organisms may provide important new insights into the various ways that organisms evolve and control the expression of their genetic information. Dr. Place says, “These studies provide a glimpse into the mechanisms responsible in the evolution of large patchwork genomes.”