Phylogeny and Genome Evolution of Oryza (Poaceae)

桑稻是世界上最重要的粮食作物。它是一个属中的两个栽培种之一(与非洲栽培稻一起，O.angberrima)，另外还有21个野生种，分布于亚洲、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(染色体数目加倍的植物)，后者被怀疑是各种二倍体(2n=24)水稻组合的稳定杂交。与美国的同事和中国博士一起，陶桑博士正致力于与水稻物种的进化和分类有关的四个主要目标：(1)从12个核的单拷贝或少拷贝基因加上叶绿体matK基因的基因序列重建水稻及其邻近草本植物的23种的系统发育；(2)利用核和叶绿体分子标记确定四倍体水稻的可能物种亲本，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物种水平系统发育解析工具包中；以及(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的分析中。桑博士已经积累了7个核基因的初步比较数据，被认为可以标记5个不同的水稻连锁群(染色体)；12个基因的目标是在组合基因分析中代表几乎所有12条染色体，以确定同源性，并区分“基因系统学”和“物种系统学”。与中国科学院植物研究所的宋戈博士合作，确保了稻属所有物种和几个外群分类群的代表性样本，通常来自多个种质。人们正在做出特别的努力来检测四倍体中同源基因座上的基因沉默或缺失的情况，并寻找这种变化中的模式，这些模式可能被证明在多倍体植物的进化中具有普遍意义。

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.