Research Sheds Light on “Dark Matter” of Genome

Most of the time, Dr. Stefano Torriani is a plant pathologist. His most recent research project revolved around the fungus Mycosphaerella graminicola where he analyzed a special class of genes that encode cell-wall-degrading enzymes. A virulent fungus relies heavily on these enzymes when attacking a plant. But while investigating these genes, Dr. Torriani came across something odd; one gene came in different sizes in different individuals. To further explore and better understand this phenomenon, the researcher deviated from his original plan and drew in other experts, including Drs. Daniel Croll, Patrick Brunner, and Eva Stukenbrock from the research group led by Dr. Bruce McDonald, Professor of Plant Pathology, ETH Zurich. What the collaborators discovered after a year of feverish research throws new light on genome evolution - but still leaves many questions unanswered. The plant pathologists quickly answered the question of why the same gene came in different lengths in different individuals. In some strains, the gene "ID-60105," which encodes for a cell-wall-digesting enzyme, had an intron; in other strains, the same gene did not have an intron. Thus, the researchers stepped into a relatively young field in biology. So-called "spliceosomal introns" were discovered only 30 years ago. Because they are non-coding regions of a gene, they provide no information on the structure of the encoded protein. Introns are separated by the coding regions, called exons. A gene, including both exons and introns, is read by the cellular machinery and transcribed into a messenger RNA. In a next step, the noncoding introns are cut away and the coding exons are spliced together. This creates the blueprint for the corresponding protein encoded by a gene.
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