Kihara Institute for Biological Research and Department of Nanobioscience, Yokohama City University, Maioka-cho 641-12, Yokohama 244-0813, Japan.
Funct Integr Genomics. 2012 Jun;12(2):341-55. doi: 10.1007/s10142-012-0269-0. Epub 2012 Feb 28.
To better understand genome structure and the expression of α/β-gliadin multigenes in hexaploid wheat, bacterial artificial chromosome (BAC) clones containing α/β-gliadin genes from the three loci, Gli-A2, Gli-B2, and Gli-D2, were screened. Based on their restriction fragment patterns, we selected five BAC clones, namely, two clones for Gli-A2, two clones for Gli-B2, and one clone for Gli-D2, to fully sequence. Approximately 200 kb was sequenced for each locus. In total, twelve α/β-gliadin intact genes and four pseudogenes were found, and retrotransposons or other transposons existed in each BAC clone. Dot-plot analysis revealed the pattern of genome segmental duplication within each BAC. We calculated time since duplication of each set of α/β-gliadin genes and insertion of retrotransposons. Duplication of all adjacent genes within the same BAC clone took place before or after allotetrapolyploidization, but duplication of certain genes occurred before diploid differentiation of wheat species. Retrotransposons were also inserted before and after the segmental duplication events. Furthermore, translocation of α/β-gliadin genes from chromosomes 1 to 6 apparently occurred before the diversification of various wheat genomes. Duplication of genome segments containing α/β-gliadin genes and retrotransposons were brought about through unequal crossing-over or saltatory replication and α/β-gliadin genes per se were duplicated without any recombination events. Out of twelve intact α/β-gliadin genes detected from their sequences, nine were expressed, although their patterns of expression were distinct. Since they have similar cis-elements and promoter structures, the mechanisms underlying their distinct gene expression and possible applications are discussed.
为了更好地理解六倍体小麦的基因组结构和 α/β-醇溶蛋白多基因的表达，我们筛选了包含来自Gli-A2、Gli-B2 和 Gli-D2 三个基因座的 α/β-醇溶蛋白基因的细菌人工染色体 (BAC) 克隆。根据它们的限制性片段模式，我们选择了五个 BAC 克隆，即两个Gli-A2 克隆、两个Gli-B2 克隆和一个Gli-D2 克隆，进行完全测序。每个基因座大约测序了 200kb。总共发现了 12 个完整的 α/β-醇溶蛋白基因和 4 个假基因，并且每个 BAC 克隆中都存在反转录转座子或其他转座子。点图分析揭示了每个 BAC 内部基因组片段重复的模式。我们计算了每一组 α/β-醇溶蛋白基因和反转录转座子插入的复制时间。同一 BAC 克隆中所有相邻基因的复制发生在多倍体化之前或之后，但某些基因的复制发生在小麦种间二倍体分化之前。反转录转座子也在片段重复事件之前和之后插入。此外，α/β-醇溶蛋白基因从染色体 1 到 6 的易位显然发生在各种小麦基因组多样化之前。包含 α/β-醇溶蛋白基因和反转录转座子的基因组片段的复制是通过不等交换或跳跃复制引起的，而 α/β-醇溶蛋白基因本身在没有任何重组事件的情况下复制。从它们的序列中检测到的 12 个完整的 α/β-醇溶蛋白基因中有 9 个被表达，尽管它们的表达模式不同。由于它们具有相似的顺式元件和启动子结构，因此讨论了它们不同基因表达的机制及其可能的应用。
