小麦族遗传资源的多样性及其保护

禾木科小麦族中包含了三种世界最重要的粮食作物,即：小麦、大麦和黑麦以及许多具有重要经济价值的牧草种类。小麦族植物种类繁多、分布广泛、生态多样,具有极其丰富的形态和遗传变异类型。作为巨大的基因资源库,小麦族植物在通过现代生物技术而导入外源有益基因的麦类作物育种程序中,具有重要和特殊的价值。然而对于小麦族植物的生物多样性的研究和了解还远远不足。同时在全球环境的不断改变和遭到破坏的今天,一些小麦族的物种已处于濒危的状态而面临灭绝,因此对于小麦族丰富的遗传多样性制定有效的措施进行保护是摆在我们面前亟待解决的课题。     

小麦族植物DNA重复序列研究

近些年来从小麦族植物中分离到了许多DNA重复序列,并对其组织结构特点,物种分布特异性和在染色体上的分布特征做了广泛的研究,其中一些重复序列已被成功地用于检测遐入小麦的外源染色质和小麦族有关种属的进化研究,本文就以上诸方面进行了简要介绍。     

Phylogenetic analysis of the genus Pseudoroegneria and the Triticeae tribe using the rbcL gene

The Pseudoroegneria species are perennial grasses in the Triticeae tribe, whose St genome has been linked to several important polyploid species. Due to frequent hybridization and complex genetic mechanism, the relationships within Pseudoroegneria, and within the Triticeae have been heavily disputed. Using the chloroplast rbcL gene we estimated the nucleotide diversity of 8 Pseudoroegneria species. We also examined the phylogenetic relationships within Pseudoroegneria and of Pseudoroegneria within the Triticeae. The estimates of nucleotide diversity indicated that Pseudoroegneria tauri and Pseudoroegneria spicata species had the highest diversity, while Pseudoroegneria gracillima had the lowest diversity. The phylogenetic analysis of Pseudoroegneria placed all P. spicata species into a clade separate from the other Pseudoroegneria species, while the relationship of the other Pseudoroegneria species could not be determined. Due to the groupings of Pseudoroegneria with the polyploid Elymus, our results strongly supported Pseudoroegneria as the maternal genome donor to Elymus. There was also weak support that P. spicata may be the maternal donor to the StH Elymus species.     

Studies on Morphological Evolution,Classification and Distribution of the Triticeae in China

_{The classification and the relationships among the genera of Chinese Triticeae were studied based on morphological characters with reference to geographical distribution and habitat conditions. The spike of Triticeae might have been derived from a panicled inflorescence like that in the Bromeae through a racemose inflorescence like the one in the Brachypodieae. There might be three evolutionary lines in the tribe. 1. Pedicels of the panicled inflorescence have become short and bracts decreased in size, which has resulted in a panicled spike with indefinite spikelets or false solitary spikelets at each node of rachis. The middle ribes of both glumes and lemmas and rachilla are not in a single plane. 2. A simple spike with usual solitary spikelets at each node of rachis has been derived from the raceme. The middle ribe of both glumes and lemmas and rachilla are in a single plane. 3. A cymose spike with 3-spikelets at each node of rachis has evolved from the cymose panicle. The glume on the central spikelet is behind the lemma, while those on the lateral spikelets are on lateral sides of the lemmas. From what we have described above Triticeae may be divided into three subtribes: Elyminae, Triticinae and Hordeinae. Then according to the morphological characters of glume, lemma and other organs as well as the habitats and distribution, the native and introduced triticeous plants are classified into 13 genera (Leymus, Elymus, Roegneria, Elytrigia, Aegilops, Triticum, Agropyron, Eremopyrum, Secale, Haynaldia, Psathyrostachys, Hordeum and Hystrix) and their relationships are also discussed meanwhile.}     

Large-scale analysis of NBS domain-encoding resistance gene analogs in Triticeae

Proteins containing nucleotide binding sites (NBS) encoded by plant resistance genes play an important role in the response of plants to a wide array of pathogens. In this paper, an in silico search was conducted in order to identify and characterize members of NBS-encoding gene family in the tribe of Triticeae. A final dataset of 199 sequences was obtained by four search methods. Motif analysis confirmed the general structural organization of the NBS domain in cereals, characterized by the presence of the six commonly conserved motifs: P-loop, RNBS-A, Kinase-2, Kinase-3a, RNBS-C and GLPL. We revealed the existence of 11 distinct distribution patterns of these motifs along the NBS domain. Four additional conserved motifs were shown to be significantly present in all 199 sequences. Phylogenetic analyses, based on genetic distance and parsimony, revealed a significant overlap between Triticeae sequences and Coiled coil-Nucleotide binding site-Leucine rich repeat (CNL)-type functional genes from monocotyledons. Furthermore, several Triticeae sequences belonged to clades containing functional homologs from non Triticeae species, which has allowed for these sequences to be functionally assigned. The findings reported, in this study, will provide a strong groundwork for the isolation of candidate R-genes in Triticeae crops and the understanding of their evolution.     

陕西、宁夏部分地区小麦族植物资源调查、收集与分类鉴定

2002年8月对陕西、宁夏部分地区分布的小麦族(Triticeae)植物进行了调查与收集,共收集小麦族植物6属、16种、145个居群,并对每一物种及其居群的分布区、生境、海拔、2n染色体数目等进行了分析。同时,对所收集材料的可利用性、调查收集的基本单元以及小麦族植物的保护进行了讨论。     

小麦族中间鹅观草不同居群的形态多样性分析

小麦族（Triticeae）植物的野外调查、收集通常是以形态学为依据的。为了探讨小麦族植物在野外调查、收集的科学取样策略,本项研究以小麦族具有自花授粉习性的3个中间鹅观草（Roegneria sinica．vat．media Keng）居群、每个居群30个单株为材料,对11个形态学性状的多样性进行了分析。结果表明,3个居群的总遗传多样性指数为1．991,遗传多样性主要集中于居群内（91．76％）,而居群间的遗传变异（8．24％）相对较小;不同取样梯度下的遗传多样性指数随单株取样数目的增加呈现增大趋势,但当取样数目达到18株时,遗传多样性指数达到最高值。上述结果说明,对于小麦族自花授粉植物野外调查、收集时,应以居群为单位,而且每一居群至少应调查、收集18个单株,才能代表居群的遗传多样性。以形态学为依据的取样策略的建立,对于指导野外调查、收集具有现实意义。     

Phylogenetic analysis of the dimeric alpha-amylase inhibitor sequences from an orthologous region in 21 different genomes of the tribe Triticeae (Poaceae)

Six hundred and thirty gene sequences from 21 different genomes in Triticeae tribe were obtained and subjected to phylogenetic analysis. The sequences showed high homology in both nucleotide sequences and length variation, and had a common conserved cysteine skeleton C–Xn–C–Xn–C–Xn–CC–Xn–C–X–C–Xn–C–Xn–C–Xn–C. The sequences from common wheat formed three clusters; two were close to Aegilops tauschii and Aegilops speltoides sequences, respectively, and the third cluster was complex with sequences from Ae. speltoides, Aegilops searsii, and Aegilops bicornis. Different S genome(s) of Aegilops contributed α-amylase inhibitor loci to polyploid wheat by gene introgression in interspecific hybridizations. No sequence from common wheat was similar to that from einkorn wheat. We conclude that the occurrence of multiple chromosomal translocations or inversions in the different genomes of Triticeae had not dramatically affected the primary structure of dimeric α-amylase inhibitors. The results revealed important information on genome shaping events and processes occurring at the dimeric α-amylase inhibitor genes loci and their bearing on the phylogenetic relationships in the tribe Triticeae (Poaceae).     

短柄草与麦类作物的比较基因组学研究进展

麦类作物是人类主要的食物来源,其遗传改良对于保障世界粮食生产具有重要作用。获得麦类作物的基因组和功能基因组信息是作物遗传育种学家解析种质资源高产及抗逆机理,并准确选择目标性状、实现分子设计育种目标的有效途径。目前,二穗短柄草（Brachypodium distachyum）是早熟禾亚科中唯一完成全基因组测序的植物。以二穗短柄草为模式植物,利用比较基因组学方法获得早熟禾亚科中基因组庞大而复杂的麦类作物的相关信息,必将加速麦类作物的遗传改良进程。本文重点介绍近十年来短柄草在麦类作物比较基因组学方面的研究进展。     

山东小麦族植物叶表皮微形态的研究

利用光学显微镜,对山东小麦族5属9种植物的叶片下表皮微形态特征进行了研究。叶片下表皮微形态在属间差异明显,可作为分属的参考依据;山东5种鹅观草属植物的叶片下表皮微形态可分为两种类型,这与形态上划分的拟披碱草组和犬草组相一致。     

An efficient Oligo-FISH painting system for revealing chromosome rearrangements and polyploidization in Triticeae

A chromosome-specific painting technique has been developed which combines the most recent approaches of the companion disciplines of molecular cytogenetics and genome research. We developed seven oligonucleotide (oligo) pools derivd from single-copy sequences on chromosomes 1 to 7 of barley (Hordeum vulgare L.) and corresponding collinear regions of wheat (Triticum aestivum L.). The seven groups of pooled oligos comprised between 10 986 and 12 496 45-bp monomers, and these then produced stable fluorescence in situ hybridization (FISH) signals on chromosomes of each linkage group of wheat and barley. The pooled oligo probes were applied to high-throughput karyotyping of the chromosomes of other Triticeae species in the genera Secale, Aegilops, Thinopyrum, and Dasypyrum, and the study also extended to some wheat-alien amphiploids and derived lines. We demonstrated that a complete set of whole-chromosome oligo painting probes facilitated the study of inter-species chromosome homologous relationships and visualized non-homologous chromosomal rearrangements in Triticeae species and some wheat-alien species derivatives. When combined with other non-denaturing FISH procedures using tandem-repeat oligos, the newly developed oligo painting techniques provide an efficient tool for the study of chromosome structure, organization, and evolution among any wild Triticeae species with non-sequenced genomes.     

披碱草属及其近源属植物种子胚乳细胞多样性研究

披碱草属不仅是小麦、大麦等作物的重要基因库,也是优良牧草的重要组成部分。胚乳是麦类作物种子的重要组成部分,其重量占籽粒重量在90%以上。胚乳特性是一个相对稳定的遗传性状,可以将胚乳特性作为植物分类和系统关系的一个指标。胚乳细胞特征作为植物的一类微形态特征,在麦类植物系统分类与进化研究中具有一定的价值。该研究对小麦族的6个披碱草属(Elymus)物种、2个拟鹅观草属(Pseudoroegneria)物种、1个大麦属(Hordeum)物种和2个冰草属(Agropyron)物种,共4属11份材料的胚乳细胞特征进行解剖观察并测量相关指标。结果表明:(1)不同属、种的植物种子胚乳细胞之间存在丰富的多样性,属间差异大于属内种间差异;(2)同样具有P染色体组的Agropyron cristatum和A.mongolicum与同样具有St染色体组的Pseudoroegneria libanotica和P.spicata各自在细胞形状和大小上的差异很小;(3)不同物种的胚乳细胞在大小、形状和数量上均表现出差异,但不能很好地反映属以及基因组间的差异,研究结果为揭示披碱草属植物的系统关系提供了胚乳细胞方面的证据,同时也为利用该属植物改良麦类作物品质积累资料。     

Dynamics of Tandem Repetitive Afa-Family Sequences in Triticeae, Wheat-Related Species

The Afa-family sequences in wheat-related species, Triticeae, are tandem repetitive sequences of 340 bp. All the analyzed Triticeae species carried the sequences in their genomes, though the copy numbers varied about 100-fold among the species. The nucleotide fragments amplified by PCR were cloned and sequenced, and their behavior in the evolution of Triticeae was analyzed by the neighbor-joining (NJ) method. The sequences in genomes with many copies of this family clustered at independent branches of the phylogenic tree, whereas the sequences in genomes with a few copies did not. This may suggest that Afa-family sequences had amplified several times in the evolution of Triticeae, each using a limited number of different master copies. In addition, the sequences of the A and B genomes of hexaploid common wheat indicated that the Afa-family sequences had not evolved in a concerted manner between the genomes. Furthermore, the sequences of each chromosome of the D genome of this species indicated that the sequences had amplified on all over the D-genome chromosomes in a short period. Received: 1 September 1997 / Accepted: 19 January 1998     

Updating of transposable element annotations from large wheat genomic sequences reveals diverse activities and gene associations

Triticeae species (including wheat, barley and rye) have huge and complex genomes due to polyploidization and a high content of transposable elements (TEs). TEs are known to play a major role in the structure and evolutionary dynamics of Triticeae genomes. During the last 5 years, substantial stretches of contiguous genomic sequence from various species of Triticeae have been generated, making it necessary to update and standardize TE annotations and nomenclature. In this study we propose standard procedures for these tasks, based on structure, nucleic acid and protein sequence homologies. We report statistical analyses of TE composition and distribution in large blocks of genomic sequences from wheat and barley. Altogether, 3.8 Mb of wheat sequence available in the databases was analyzed or re-analyzed, and compared with 1.3 Mb of re-annotated genomic sequences from barley. The wheat sequences were relatively gene-rich (one gene per 23.9 kb), although wheat gene-derived sequences represented only 7.8% (159 elements) of the total, while the remainder mainly comprised coding sequences found in TEs (54.7%, 751 elements). Class I elements [mainly long terminal repeat (LTR) retrotransposons] accounted for the major proportion of TEs, in terms of sequence length as well as element number (83.6% and 498, respectively). In addition, we show that the gene-rich sequences of wheat genome A seem to have a higher TE content than those of genomes B and D, or of barley gene-rich sequences. Moreover, among the various TE groups, MITEs were most often associated with genes: 43.1% of MITEs fell into this category. Finally, the TRIM and copia elements were shown to be the most active TEs in the wheat genome. The implications of these results for the evolution of diploid and polyploid wheat species are discussed. Electronic Supplementary Material Supplementary material is available for this article at     

麦类作物遗传转化

麦类作物包括小麦(Triticum aestivum L.)、硬粒小麦(Triticum turgidum con v.durum Dest.e.m)、大麦(Hordeum vulgare L.)、黑麦(Secale cereal L.)、燕麦(Avena sativa L.)及小大麦(×Tritordeum Ascherson et Graebuer.).自从基因枪被发明以来,科学家们已经利用来自麦类作物的幼胚、 盾片、成熟种子胚、花粉粒、花药、幼穗、叶基组织、发芽种子幼苗的顶端分生组织及其愈伤组织或培养物作为外植体,通过基因枪、农杆菌介导、 PEG法、电激法、微注射法、硅化纤维素介导、幼穗注射法等技术先后将一些选择标记基因、报告基因和有用的目的基因如抗真菌、抗虫、 籽粒品质、抗干旱基因等转化到麦类作物中.转基因植物表现为抗性增强或籽粒的加工品质提高和营养成份增加.被转化的基因通常以单位点多拷贝的形式随机整合到受体细胞的基因组中,并以孟德尔规律遗传.整合位点一般分布在染色体的近端粒区域,整合的拷贝数大多为5～10个拷贝,最高可达到50个拷贝.在转化过程中,被转化的质粒上的片段包括选择标记基因、目标基因、甚至质粒的抗生素基因和其他无关序列,随机地连接并形成多个分子量大小不等,组成成分不同的分子簇,或首先由其中一个分子簇整合到植物基因组中,这会导致在整合位点附近产生"热点",易于其他分子簇在此处整合,从而完成两期整合;或被转化的质粒上的选择标记基因、目标基因、质粒的抗生素基因和其他无关序列、植物基因组DNA等片段共同形成各种不同类型的分子簇,当植物细胞染色体复制时,在复制叉处整合到植物基因组中.转基因可以在各种水平上表达,也会时常发生基因沉默,这会导致转基因植物DNA水平上表达但在蛋白质水平上不表达,后代偏向分离,沉默的转基因重新表达.转基因的位置效应、甲基化和启动子都会诱发转基因沉默.在麦类作物中,35S启动子易于导致转基因沉默,应尽量减少使用.转基因还导致被转化麦类作物在农艺性状和细胞学上的变异.目前,麦类作物遗传转化已经成为一种常规的技术,转基因麦类作物正开始进入商业应用阶段.相信多种转化新技术的应用和发展将会培育出高产、稳产、优质、低投入的各类品种和种质.     

麦类作物遗传转化(英)

麦类作物包括小麦 (TriticumaestivumL .)、硬粒小麦 (Triticumturgidumconv .durumDest.e.m)、大麦 (HordeumvulgareL .)、黑麦 (SecalecerealL .)、燕麦 (AvenasativaL .)及小大麦 (×TritordeumAschersonetGraebuer.)。自从基因枪被发明以来 ,科学家们已经利用来自麦类作物的幼胚、盾片、成熟种子胚、花粉粒、花药、幼穗、叶基组织、发芽种子幼苗的顶端分生组织及其愈伤组织或培养物作为外植体 ,通过基因枪、农杆菌介导、PEG法、电激法、微注射法、硅化纤维素介导、幼穗注射法等技术先后将一些选择标记基因、报告基因和有用的目的基因如抗真菌、抗虫、籽粒品质、抗干旱基因等转化到麦类作物中。转基因植物表现为抗性增强或籽粒的加工品质提高和营养成份增加。被转化的基因通常以单位点多拷贝的形式随机整合到受体细胞的基因组中 ,并以孟德尔规律遗传。整合位点一般分布在染色体的近端粒区域 ,整合的拷贝数大多为 5～ 10个拷贝 ,最高可达到 5 0个拷贝。在转化过程中 ,被转化的质粒上的片段包括选择标记基因、目标基因、甚至质粒的抗生素基因和其他无关序列 ,随机地连接并形成多个分子量大小不等 ,组成成分不同的分子簇 ,或首先由其中一个分子簇整合到植物基因组中 ,这会导致在整合位点附近产生“热点     

Fertile transgenic plants obtained from tritordeum inflorescences by tissue electroporation

 Tissue electroporation was applied to a member of the Triticeae family, namely tritordeum (Hordeum chilense Roem.×Triticum turgidum L. Conv. durum), for the generation of fertile transgenic plants. Two transgenic plants were recovered following the treatment of 361 explants of immature inflorescences (although they were subsequently found to result from the same transformation event). The expression of both inserted marker genes (uidA and bar) was confirmed using standard assays, while transgene integration was confirmed using PCR and Southern hybridization analyses. Integration pattern, segregation ratio and the inheritance of transgene expression in T₁ progeny were consistent for the presence of a single transgene locus containing five to ten plasmid insertions. Although this procedure has been applied to other cereal species, stable transformation of the Triticeae using tissue electroporation has not previously been reported. Received: 28 October 1999 / Revision received: 25 August 2000 / Accepted: 29 August 2000     

小麦族四个属模式种的醇溶蛋白分析

利用酸性聚丙烯酰胺凝胶电泳 (APAGE)对小麦族披碱草属、鹅观草属、猬草属和仲彬草属 4个属的模式种进行了醇溶蛋白电泳分析 ,结果表明 :(1 ) 4个模式种具有明显的醇溶蛋白遗传多样性 ,其种间醇溶蛋白多态性高达 92 .3 % ;(2 ) Elymus sibiricus和 H ystrix patula具有相似的醇溶蛋白带型 ,而 Roegneria caucasica和Kengyilia gobicola的带型基本相似 ,其醇溶蛋白图谱能够反映一定的系统关系 ;(3 )不同收集地的 E. sibiricus材料间也存在明显的醇溶蛋白遗传差异 ,新疆的 E. sibiricus具有较丰富的醇溶蛋白带纹 ,而甘肃的 E. sibiricus的醇溶蛋白带纹较少。     

Sequence composition, organization, and evolution of the core Triticeae genome

We investigated the composition and the basis of genome expansion in the core Triticeae genome using Aegilops tauschii, the D-genome donor of bread wheat. We sequenced an unfiltered genomic shotgun (trs) and a methylation-filtration (tmf) library of A. tauschii, and analyzed wheat expressed sequence tags (ESTs) to estimate the expression of genes and transposable elements (TEs). The sampled D-genome sequences consisted of 91.6% repetitive elements, 2.5% known genes, and 5.9% low-copy sequences of unknown function. TEs constituted 68.2% of the D-genome compared with 50% in maize and 14% in rice. The DNA transposons constituted 13% of the D-genome compared with 2% in maize. TEs were methylated unevenly within and among elements and families, and most were transcribed which contributed to genome expansion in the core Triticeae genome. The copy number of a majority of repeat families increased gradually following polyploidization. Certain TE families occupied discrete chromosome territories. Nested insertions and illegitimate recombination occurred extensively between the TE families, and a majority of the TEs contained internal deletions. The GC content varied significantly among the three sequence sets examined ranging from 42% in tmf to 46% in trs and 52% in the EST. Based on enrichment of genic sequences, methylation-filtration offers one option, although not as efficient as in maize, for isolating gene-rich regions from the large genome of wheat.