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The figure shows a schematic image of an rRNA cluster in fungi. ITS stands for Internal Transcribed Spacer and IGS for InterGenic spacer. - Click on the image to enlarge it.
ITS sequences means "Internal Transcribed Spacer" sequences and refers to the DNA segments that lie between the rRNA genes in the rRNA operon. Eukaryotic organisms have four different rRNA molecules: 5S, 5.8S, 18S and 26S rRNA or 28S rRNA. The genes for rRNA molecules are organized in clusters or operons and between the genes there are ITS sequences. These clusters are present in many copies in the genome and the figure shows how rRNA genes, ITS sequences and IGS (InterGenic spacer) sequences are organized in the genomes of fungi.
For the identification and phylogenetic studies of fungi, ITS sequences have proven to be very useful and these sequences are called molecular barcodes. Thanks to the variability in ITS, sequence analysis can provide information about family affiliation and often also species affiliation. Sometimes geographical variants can also be identified, which is useful in epidemiology. In the fungus pages in AgriMyc, links will be provided to ITS sequences deposited in the GenBank database. Fungi have two ITS sequences, while bacteria only have one such gene.