Submitted to: Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/8/2003
Publication Date: 5/3/2003
Citation: FARIS, J.D., FELLERS, J.P., BROOKS, S.A., GILL, B.S. A BACTERIAL ARTIFICIAL CHROMOSOME CONTIG SPANNING THE MAJOR DOMESTICATION LOCUS Q IN WHEAT AND IDENTIFICATION OF A CANDIDATE GENE. GENETICS. 2003. VOL. 164:311-321. Interpretive Summary: Crop plants have undergone certain genetic changes through evolution that allowed them to become domesticated. For domesticated bread wheat, the free-threshing characteristic of the spike is probably the most important domestication trait. The Q gene is responsible for conditioning the free-threshing character, and it also influences other important traits such as rachis toughness, glume tenacity, spike length, and plant height. The Q gene has been located on the long arm of chromosome 5A in wheat. We sequenced a contiguous segment of 300,000 bp of DNA spanning the Q gene. From this, we narrowed the position of Q to a segment less than 100,000 bp and identified a candidate gene sequence which is likely to be the Q gene. Experiments to verify that the candidate gene is actually the Q gene are ongoing. Once the Q gene is isolated, we will be able to study the regulatory effects that Q has on other genes and dissect the biochemical pathways. Furthermore, Q may be used to domesticate other wild wheat species by transformation, rendering them useful for cultivation in order to exploit value added traits.
Technical Abstract: The Q locus played a major role in the domestication of wheat because it confers the free-threshing character and influences many other agronomically important traits. We constructed a physical contig spanning the Q locus using a Triticum monococcum BAC library. Four chromosome walking steps were performed by complete sequencing of BACs and identification of low-copy markers through homology searches of database sequences. The BAC contig spans a physical distance of about 300 kb corresponding to a genetic distance of 0.9 cM. The physical map of T. monococcum had perfect colinearity with the genetic map of wheat chromosome arm 5AL. Recombination data in conjunction with analysis of fast-neutron deletions confirmed that the contig spanned the Q locus. The Q gene was narrowed to a 100 kb segment which contains an APETALA2 (AP2)-like gene that cosegregates with Q. AP2 is known to play a major role in controlling floral homeotic gene expression and thus, is an excellent candidate for Q.