Brooks Steven A, Huang Li, Gill Bikram S, Fellers John P
Department of Plant Pathology, Kansas State University, Manhattan 66506, USA.
Genome. 2002 Oct;45(5):963-72. doi: 10.1139/g02-049.
Vast differences exist in genome sizes of higher plants; however, gene count remains relatively constant among species. Differences observed in DNA content can be attributed to retroelement amplification leading to genome expansion. Cytological and genetic studies have demonstrated that genes are clustered in islands rather than distributed at random in the genome. Analysis of gene islands within highly repetitive genomes of plants like wheat remains largely unstudied. The objective of our work was to sequence and characterize a contiguous DNA sequence from chromosome IDS of Aegilops tauschii. An RFLP probe that maps to the Lr21 region of IDS was used to isolate a single BAC. The BAC was sequenced and is 106 kb in length. The contiguous DNA sequence contains a 46-kb retroelement-free gene island containing seven coding sequences. Within the gene island is a complex arrangement of resistance and defense response genes. Overall gene density in this BAC is 1 gene per 8.9 kb. This report demonstrates that wheat and its relatives do contain regions with gene densities similar to that of Arabidopsis.
高等植物的基因组大小存在巨大差异；然而，不同物种间的基因数量相对恒定。观察到的DNA含量差异可归因于逆转录元件扩增导致基因组扩张。细胞学和遗传学研究表明，基因聚集在基因岛中，而非随机分布于基因组中。对于像小麦这样具有高度重复基因组的植物，其基因岛的分析在很大程度上仍未得到研究。我们工作的目标是对节节麦（Aegilops tauschii）ID染色体上的一段连续DNA序列进行测序并加以表征。一个定位于ID染色体Lr21区域的RFLP探针被用于分离单个BAC。该BAC被测序，长度为106 kb。这段连续DNA序列包含一个46 kb的无逆转录元件基因岛，其中含有七个编码序列。在基因岛内，抗性和防御反应基因呈复杂排列。该BAC中的总体基因密度为每8.9 kb有1个基因。本报告表明，小麦及其近缘物种确实含有基因密度与拟南芥相似的区域。
