W223 Chromosome Synteny in Cucumis Species

Date: Sunday, January 15, 2012
Time: 5:10 PM
Room: Pacific Salon 1
Yiqun Weng , USDA ARS/ Universtiy of Wisconsin, Madison, WI
Luming Yang , University of Wisconsin-Madison, Madison, WI
Dal-Hoe Koo , University of Wisconsin - Madison, Madison, WI
Dawei Li , University of Wisconsin - Madison, Madison, WI
Jiming Jiang , University of Wisconsin-Madison, Madison, WI
Michael J. Havey , University of Wisconsin, Madison, WI
Cucumber, Cucumis sativus L. (2n = 2x = 14) and melon, C. melo L. (2n = 2x = 24) are two important vegetable species in the genus Cucumis (family Cucurbitaceae). Two inter-fertile botanical varieties with 14 chromosomes, the cultivated C. sativus var. sativus L. and the wild C. sativus var. hardwickii (Royle) Alef., comprise the primary gene pool of cucumber. Cucumber is believed to have evolved from a n=12 common ancestor of melon through chromosome fusion, but the details of this process are largely unknown. Our knowledge of chromosome evolution during domestication of cultivated cucumber is also very limited. In this study, a high-resolution genetic map of cultivated cucumber was constructed and anchored to whole genome scaffolds. The completeness of this linkage map was verified by fluorescence in situ hybridization (FISH) with fosmid clones. At least six inversions were identified between cultivated (C.s. var. sativus) and wild (C.s. var. hardwickii) cucumbers. Comparative genetic mapping between cucumber and melon suggested that Chromosome 7 of cucumber is syntenic to Chromosome I of melon. Chromosomes 2 and 6 of cucumber each contained genomic regions syntenic to melon chromosomes III+V+XI and III+VIII+XI, respectively.  Likewise, Chromosomes 1, 3, 4, and 5 of cucumber each are syntenic with genomic regions of two melon chromosomes previously designated as II+XII, IV+VI, VII+VIII, and IX+X, respectively. However, comparison of marker orders in several syntenic blocks suggested more complicated structural changes beyond simple chromosome fusion events since the evolution of cucumber from a 2n = 24 ancestor. Interestingly, comparative FISH among several Cucurbitaceae species suggested that Chromosome 7 of wild cucumber has remained largely intact over the last twenty million years. Many structural changes may have occurred during the evolution of the remaining six cucumber chromosomes.