ARS | Publication request: Chromatin structure and physical mapping of chromosome 6 of potato and comparative analyses with tomato

Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 2, 2008
Publication Date: November 1, 2008
Citation: Iovene, M., Wielgus, S.M., Simon, P.W., Buell, C.R., Jiang, J. 2008. Chromatin structure and physical mapping of chromosome 6 of potato and comparative analyses with tomato. Genetics. 180(3):1307-1317.

Interpretive Summary: Genetic experiments have long suggested that genes are on chromosomes, but it has not often been demonstrated that this is true. Many genes of potato are thought to be located on chromosome number 6. In this study, short pieces of DNA with 25 chromosome 6 genes were visually associated with that chromosome. This visualization was done by using fluorescent labeling of these short pieces of DNA to actually see where the genes are located. All genes were proven to be located in the linear order they were expected, but some distances between genes were greater or less than expected. This same potato chromosome was compared to an equivalent chromosome in tomato, which is a close relative. With the exception of one short region (where gene order was inverted), the potato and tomato chromosomes had the same linear order of genes. This study is of interest to geneticists studying genes and chromosomes, to taxonomists studying how chromosomes change in evolution, and plant breeders interested in moving genes during the plant breeding process.

Technical Abstract: Potato (Solanum tuberosum) has the densest genetic linkage map and one of the earliest established cytogenetic maps among all plant species. However, there has been limited effort to integrate these maps. Here, we report fluorescence in situ hybridization (FISH) mapping of 25 genetic marker-anchored bacterial artificial chromosome (BAC) clones on the pachytene chromosome 6 of potato. The FISH mapping results allowed us to define the genetic positions of the centromere and the pericentromeric heterochromatin and to relate chromatin structure to the distribution of recombination along the chromosome. A drastic reduction of recombination was associated with the pericentromeric heterochromatin which accounts for approximately 27% of the physical length of the pachytene chromosome. The pachytene chromosome 6 of tomato (Solanum lycopersicum) and potato share a similar morphology. However, distinct differences of heterochromatin distribution were observed between the two chromosomes. Mapping of several potato BACs on tomato pachytene chromosome 6 revealed an overall colinearity between the two chromosomes. A previously unreported chromosome inversion was observed in the euchromatic region of the short arms. These results show that the potato and tomato genomes contain more chromosomal rearrangements than those reported previously based on comparative genetic linkage mapping.