Department of Biological Sciences, Purdue University, 47907, W. Lafayette, IN, USA.
Theor Appl Genet. 1989 Jun;77(6):844-50. doi: 10.1007/BF00268337.
The structure and organization of the ribosomal DNA (rDNA) of sorghum (Sorghum bicolor) and several closely related grasses were determined by gel blot hybridization to cloned maize rDNA. Monocots of the genus Sorghum (sorghum, shattercane, Sudangrass, and Johnsongrass) and the genus Saccharum (sugarcane species) were observed to organize their rDNA as direct tandem repeats of several thousand rDNA monomer units. For the eight restriction enzymes and 14 cleavage sites examined, no variations were seen within all of the S. bicolor races and other Sorghum species investigated. Sorghum, maize, and sugarcane were observed to have very similar rDNA monomer sizes and restriction maps, befitting their close common ancestry. The restriction site variability seen between these three genera demonstrated that sorghum and sugarcane are more closely related to each other than either is to maize. Variation in rDNA monomer lengths were observed frequently within the Sorghum genus. These size variations were localized to the intergenic spacer region of the rDNA monomer. Unlike many maize inbreds, all inbred Sorghum diploids were found to contain only one rDNA monomer size in an individual plant. These results are discussed in light of the comparative timing, rates, and modes of evolutionary events in Sorghum and other grasses. Spacer size variation was found to provide a highly sensitive assay for the genetic contribution of different S. bicolor races and other Sorghum species to a Sorghum population.
高粱（高粱属）及其几个近缘禾本科植物的核糖体 DNA（rDNA）的结构和组织通过与克隆的玉米 rDNA 的凝胶印迹杂交来确定。高粱属（高粱、碎米高粱、苏丹草和约翰逊草）和甘蔗属（甘蔗种）的单子叶植物被观察到将其 rDNA 组织为几千个 rDNA 单体单位的直接串联重复。在所研究的 8 种限制酶和 14 个切割位点中，没有观察到所有 S. bicolor 品种和其他高粱种之间的变化。高粱、玉米和甘蔗被观察到具有非常相似的 rDNA 单体大小和限制图谱，这与其密切的共同祖先相符。这三个属之间的限制位点变化表明，高粱和甘蔗彼此之间的亲缘关系比与玉米更为密切。高粱属内经常观察到 rDNA 单体长度的变化。这些大小变化定位于 rDNA 单体的基因间间隔区。与许多玉米自交系不同，所有自交高粱二倍体在单个植物中仅含有一种 rDNA 单体大小。这些结果是根据高粱和其他禾本科植物进化事件的比较时间、速度和模式进行讨论的。间隔大小的变化被发现为高粱种群中不同 S. bicolor 品种和其他高粱种的遗传贡献提供了一种高度敏感的测定方法。
