|Jacobus, Barbara Hass|
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2005
Publication Date: 7/1/2005
Citation: Lin, J., Jacobus, B., Sanmiguel, P., Walling, J., Yuan, Y., Shoemaker, R.C., Young, N., Jackson, S. 2005. Centric regions of soybean (Glycine max L. merr.) chromosomes consist of retroelements and tandemly repeated DNA and are structurally and evolutionarily labile. Genetics. 170:1221-1230. Interpretive Summary: The organization of plant chromosomes is often complex. Understanding how the many repetitive DNA elements are organized is essential to planning whole-genome sequencing projects. In this study the authors used a combination of molecular techniques, DNA cloning, and high-powered microscopy to identify specific regions on all 20 soybean chromosomes that contain many of the same repetititve sequences. They determined that some of the sequences are unique to soybean and its closest relative. These findings are important pieces of information about the evolution of soybean chromosomes and will be useful to geneticists and evolutionary biologists. This information will be essential to the planning of large-scale genomics projects designed to decode the hereditary information of soybean chromosomes.
Technical Abstract: Little is known about the physical makeup of the soybean (Glycine max L. merr.) genome apart from its size and chromosome number. Using DNA sequencing and molecular cytogenetics, an initial analysis of the repetititve fraction of the soybean genome is presented. BAC076J21, derived from Linkage Group L, has sequences conserved in the pericentromeric heterochromatin of all 20 chromosomes. FISH analysis of this BAC and three subclones on pachytene chromosomes revealed relatively strict partitioning of the heterochromatic and euchromatic regions. Sequence analysis showed that this BAC consists primarily of repetitive sequences such as a 102 bp tandem repeat with sequence identity to apreviously charactrerized ~120 bp repeat (STR120). Fragments of Calypso-like retroelements, a recently inserted SIRE1 element and a SIRE1 solo-LTR were present within this BAC. Some of these sequences are methylated and are not conserved outside of G. max and G. soja, a close relative of soybean, except for STR102 that hybridized to a restriction fragment from G. latifolia. These data present a picture of the repetitive fraction of the soybean genome that is highly concentrated in the pericentromeric regions, consisting of rapidly evolving tandem repeats with interspersed retroelements.