谷类作物基因结构及其数量的比较

Comparison of structure and numbers of genes among cereals

本文综述了谷类作物基因组结构现状,基于水稻和拟南芥全基因组分析以及谷类作物基因组长片段的测序注释表明,谷类作物基因组存在许多嵌合结构,富基因岛重组上活性部分常被高拷贝DNA模块分隔.谷类作物基因组内,具保守的宏共线性.玉米,水稻,高梁,小麦,及大麦的Sh2/A1直向同源区域的基因顺序分析表明,Sh2和A1同系物间隔分别为20kb(在水稻和高梁)和140kb(在玉米);小麦族Sh2/A1区同线性在X1和X2基因间有一个断裂.如同其他禾本科作物,A1和X2基因在部分同源染色体保留共线性,Sh2和X1直向同源依然是共线性,但在非部分同源染色体的位置已改变.植物基因可以通过多倍体化,节段重复及局部基因扩增3种途径增加序列的数量.单个基因内,微共线性常被破坏.对基因组直向同源区段的初步比较分析暗示,植物基因组内基因局部扩增和易位也许有某些关联.

This review describes the current state of knowledge regarding cereal genome structure. Annotation based on the sequencing of long genomic segments from cereals and the whole-genome analyses of Arabidopsis and rice,suggests that a mosaic structure consisting of recombinationally active gene-rich islands that are separated by blocks of high-copy DNA. Macrocolinearity within the cereals is conserved. By analysing the gene order of the Sh_2/A_1 orthologous region of maize, rice, sorghum, wheat, and barley, the Sh_2 and A_1 homologs are separated by 20 kb in rice and sorghum and by 140 kb in maize. The synteny in the Sh_2/A_1 region is interrupted by a break between the X_1 and X_2 genes in the triticeae. The colinear between A_1 and X_2 genes remains in homeologous chromosomes as in other grasses, but that between Sh_2 and X_1 orthologs were translocated to a nonhomeologous chromosome. Through three forms of duplication, i.e. polyploidization, segmental duplication, and local gene amplification, increases the number of paralogous gene sequences found in plants. At the level of individual genes, microcolinearity is frequently disrupted. Preliminary evidence from comparative analysis of sequenced orthologous genomic segments suggests that local gene amplification and translocation within a plant genome may be linked in some cases.