Li Wanlong, Gill Bikram S
Wheat Genetics Resource Center, Department of Plant Pathology, Kansas State University, Manhattan, KS 66506-5502, USA.
Funct Integr Genomics. 2006 Oct;6(4):300-9. doi: 10.1007/s10142-005-0015-y. Epub 2006 Jan 11.
Shattering is an essential seed dispersal mechanism in wild species. It is believed that independent mutations at orthologous loci led to convergent domestication of cereal crops. To investigate genetic relationships of Triticeae shattering genes with those of other grasses, we mapped spike-, barrel- (B-type), and wedge-type (W-type) spikelet disarticulation genes in wheat and its wild relatives. The Br1 gene for W-type disarticulation was mapped to a region delimited by Xpsr598 and Xpsr1196 on the short arm of chromosomes 3A in Triticum timopheevii and 3S in Aegilops speltoides. The spike- and W-type disarticulation genes are allelic at Br1 in Ae. speltoides. The B-type disarticulation gene, designated as Br2, was mapped to an interval of 4.4 cM between Xmwg2013 and Xpsr170 on the long arm of chromosome 3D in Aegilops tauschii, the D-genome donor of common wheat. Therefore, B- and W-type disarticulations are governed by two different orthologous loci on group-3 chromosomes. Based on map position, orthologs of Br1 and Br2 were not detected in barley, maize, rice, and sorghum, indicating multiple genetic pathways for shattering in grasses. The implications of the mapping results are discussed with regard to the evolution of polyploid wheat and domestication of cereals.
破碎是野生植物中一种重要的种子传播机制。人们认为，直系同源位点的独立突变导致了谷类作物的趋同驯化。为了研究小麦族破碎基因与其他禾本科植物破碎基因之间的遗传关系，我们对小麦及其野生近缘种中的穗型、桶型（B型）和楔形（W型）小穗脱节基因进行了定位。控制W型脱节的Br1基因被定位到提莫菲维小麦3A染色体短臂上由Xpsr598和Xpsr1196界定的区域，以及斯卑尔脱山羊草3S染色体上的相同区域。在斯卑尔脱山羊草中，穗型和W型脱节基因在Br1位点上是等位基因。控制B型脱节的基因，命名为Br2，被定位到普通小麦D基因组供体节节麦3D染色体长臂上Xmwg2013和Xpsr170之间4.4 cM的区间内。因此，B型和W型脱节受3组染色体上两个不同的直系同源位点控制。基于图谱位置，在大麦、玉米、水稻和高粱中未检测到Br1和Br2的直系同源基因，这表明禾本科植物中存在多种破碎遗传途径。我们讨论了这些定位结果对多倍体小麦进化和谷类作物驯化的意义。
