Submitted to: Genome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2001
Publication Date: 5/2/2002
Citation: BROOKS,S., HUANG,L., GILL,B.S., FELLERS,J.P., ANALYSIS OF 106 KB OF CONTIGUOUS DNA SEQUENCE FROM THE D GENOME OF WHEAT REVEALS HIGH GENE DENSITY AND A COMPLEX ARRANGEMENT OF GENES RELATED TO DISEASE RESISTANCE, GENOME RESEARCH, 2002. Interpretive Summary: DNA sequencing technology is allowing researchers to unlock the genetic secrets of life. In plants, the weedy plant Arabidopsis thaliana has had its entire genome deciphered. Cereals, like rice and wheat, have yet to have their genome sequenced. This manuscript describes the results of a sequencing project on a small portion of the wheat genomes. We have found that wheat contains concentrated regions of genes along its chromosomes. What is unique about this work is that the genes in this concentrated block are involved in making the plant resistant to various diseases. This is the first report of such a high concentration of genes in all of the cereals. Also found was a significant number of nucleotide repeat regions that can be used as molecular markers for this region.
Technical Abstract: Vast differences exist in genome sizes of higher plants; however, gene count remains relatively constant among species. Differences observed in DNA content can be attributed to retroelement amplification leading to genome expansion. Cytological and genetic studies have demonstrated that genes are clustered in islands rather than distributed at random in the genome. Analysis of gene islands within highly repetitive genomes of plants such as wheat remains largely unstudied. The objective of our work was to sequence and characterize a contiguous DNA sequence from chromosome 1DS of Aegilops tauschii. An RFLP probe that maps to the Lr21/40 region of 1DS was used to isolate a single BAC. The BAC was sequenced and is 106 Kb in length. The contiguous DNA sequence contains a 54 Kb retroelement-free gene island containing 9 coding sequences. Within the gene island is a complex arrangement of 2 resistance and 2 defense response genes. Gene density in this BAC is 1 gene per 6.7 Kb. This report demonstrates that wheat and its relatives do contain regions with gene densities similar to that of Arabidopsis.