Phylogeny and Genome Evolution of Oryza (Poaceae)

[00:89701]水稻（Oryza sativa）是世界上最重要的粮食作物。它是一个属中两个栽培种（与非洲栽培稻O. glaberrima）之一，另外还有21个野生种，分布在亚洲、非洲、澳大利亚和拉丁美洲。二倍体和四倍体都是已知的物种（染色体数量加倍的植物），后者被怀疑是二倍体（2n=24）水稻的各种组合的稳定杂交。与美国和中国的同事一起，Tao Sang博士正在解决与水稻物种进化和分类相关的四个主要目标：(1)从12个核单拷贝或少拷贝基因加上叶绿体matK基因的基因序列中重建23种水稻及其附近的草类近亲的系统发育；(2)利用核和叶绿体分子标记确定四倍体水稻可能的物种亲本，包括可能的母本；(3)将新的单拷贝或低拷贝核基因添加到系统学家的工具包中，以进行物种水平的系统发育解决；(4)将基因组学方法与现代系统实践相结合，特别是在杂交和多倍体分析方面。桑博士已经积累了7个核基因的初步比较数据，被认为标记了水稻的5个不同的连锁群（染色体）；这12个基因的目标是在组合基因分析中代表几乎所有的12条染色体，以确定一致性并区分“基因系统发生”和“物种系统发生”。与中国科学院植物研究所的宋戈博士合作，确保了稻谷所有物种和几个外群分类群的代表性采样，通常来自多个资料。目前正在作出特别努力，以发现四倍体中同源位点上基因沉默或缺失的情况，并在这些变化中寻找可能证明在多倍体植物进化中具有普遍意义的模式。

0089701Sang Rice, Oryza sativa, is the world's most important food crop. It is one of two cultivated species (with African cultivated rice, O. glaberrima) in a genus with 21 additional wild species, distributed in Asia, Africa, Australia, and Latin America. Both diploid and tetraploid species are known (plants with double the number of chromosomes), the latter suspected to be stabilized hybrids of various combinations of diploid (2n=24) rices. With colleagues in the U.S. and China, Dr. Tao Sang is addressing four major goals related to the evolution and classification of rice species: (1) reconstruct a phylogeny of the 23 species of Oryza and nearby grass relatives from gene sequences from 12 nuclear single- or few-copy genes plus the chloroplast matK gene; (2) determine with nuclear and chloroplast molecular markers the likely species parentage of the tetraploid rices, including the likely maternal parent; (3) add new single-copy or low-copy nuclear genes to the systematist's toolkit for species-level phylogenetic resolution; and (4) integrate genomic methods with modern systematic practices, particularly in the analysis of hybrids and polyploids. Dr. Sang has accumulated preliminary comparative data for 7 nuclear genes already, thought to mark 5 different linkage groups (chromosomes) of rice; the goal of the 12 genes is to represent nearly all 12 chromosomes in combined-genes analyses, to determine congruence and distinguish "gene phylogenies" from "species phylogenies." Collaboration with Dr. Song Ge at the Institute of Botany, Chinese Academy of Sciences has ensured representative sampling of all species of Oryza and of several outgroup taxa, usually from multiple accessions. Special efforts are being made to detect cases of gene silencing or deletion at homoeologous loci in the tetraploids, and to search for patterns in such changes that may prove of general significance in the evolution of polyploid plants.