Enantiomeric resolution of p-toluenesulfonate of valine benzyl ester by preferential crystallizaion

Preferential crystallization of amino acid derivatives by seeding a pure enantiomer into racemic amino acid solutions has been studied for many years. However, few examples of valine derivatives have been reported so far. Although there have been some reports using valine hydrogen chloride with preferential crystallization, it is difficult to obtain optical isomers for valine derivatives using preferential crystallization. In this study, repeated preferential crystallization of p-toluenesulfonate valine benzyl ester with a 20% e.e. in 2-propanol gave a 94% e.e. on sonication. Sonication accelerated crystallization rate, but there was not a big difference in e.e. between with and without sonication. However, this research demonstrates the first preferential crystallization of p-toluenesulfonate of valine benzyl esters with an acceleration of crystallization using sonication.     

Cytoplasmic and genomic effects on meiotic pairing in brassica hybrids and allotetraploids from pair crosses of three cultivated diploids

Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and "fixed heterosis" in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids.     

随机配对法在亚高山草甸优势种群格局分析中的应用

随机配对法是植物种群格局分析的主要方法之一,理论上讲它是最好的方法,因为他改进了等级方差法的所有缺点.但该方法还没有在我国研究实践中应用过.本文将随机配对法应用于芦芽山亚高山草甸群落优势种群的格局研究.结果较好地反映了种群的空间特征.该方法分辨力较强,可以揭示各种格局规模.     

Observations on the division characterization of diploid nuclear in <Emphasis Type="Italic">Porphyra</Emphasis> (Bangiales,Rhodophyta)

Nuclear divisions of carpospores, conchocelis and conchospores of Porphyra yezoensis, P. haitanensis, P. katadai var. hemiphylla and P. oligospermatangia from China were investigated. The observations showed diploid chromosome numbers of 2n = 6 for P. yezoensis and P. oligospermatangia, and 2n = 10 for P. haitanensis and P. katadai var. hemiphylla. For all four species, somatic pairing of chromosome sets was observed in late prophase. Sister chromosomes separated at anaphase as mitosis took place in carpospores, conchocelis filamentous cells, conchosporangial branch cells and sporangial cells (conchospore formation). Chromosome configurations of tetrad and ring-shaped in conchospore germination were observed, demonstrating the occurrence of meiosis. The characteristics of diploid nuclear division in 2n = 6 species are the same as those of 2n = 10 species. The influence of somatic pairing on nuclear division of diploid cells in Porphyra was discussed.     

Crossability of Brassica tournefortii and B. rapa, and morphology and cytology of their F1 hybrids

The crossability between Brassica tournefortii (TT, 2n = 20) and Brassica rapa (AA, 2n = 20) and the cytomorphology of their F₁ hybrids were studied. Hybrids between these two species were obtained only when B. tournefortii was involved as a female parent. The hybrid plants were intermediate for most of the morphological attributes and were found to be free from white rust under field conditions. The F₁ plants showed poor pollen fertility, although occasional seed set was achieved from open pollination. Self-pollination or backcrosses did not yield any seeds in these plants. The occurrence of chromosome association ranging from bivalents (0–7), trivalents (0–2) to a rare quadrivalent (0–1) in the dihaploid hybrids indicates pairing between the T and A genomes. The homoeologous pairing coupled with seed set in the F₁ plants offer an opportunity for interspecific gene transfers from B. tournefortii to B. rapa and vice-versa through interspecific hybridization. Received: 3 July 2000 / Accepted: 22 September 2000     

Genetic dissection of a modern sugarcane cultivar (Saccharum spp.). I. Genome mapping with AFLP markers

Sugarcane cultivars are polyploid, aneuploid clones derived from interspecific hybridization between Saccharum officinarum and S. spontaneum. Their genome has recently started to be unravelled as a result of the development of molecular markers. We constructed an AFLP genetic map based on a selfing population of a specific cultivar, R570.Using 37 AFLP primer pairs, we detected 1,185 polymorphic markers of which 939 were simplex (segregated 3:1); these were used to construct the map. Of those 939, 887 were distributed on 120 cosegregation groups (CGs) based on linkages in coupling, while 52 remained unlinked. The cumulative length of all the groups was 5,849 cM, which is probably around one-third of the total genome length. Comparison with reference S. officinarum clones enabled us to assign 11 and 79 CGs to S. spontaneum and S. officinarum,respectively, whereas 11 CGs were probably derived from recombination between chromosomes of the two ancestral species. The patchy size of the groups, which ranges from 1 to 232 cM, illustrates the difficulty to access large portions of chromosomes, particularly those inherited from S. officinarum. Repulsion phase linkages suggested a high preferential pairing for 13 CG pairs. Out of the 120 CGs, 34 could be assigned to one of the 10 homo(eo)logy groups already defined in a previous RFLP map owing to the use of a small common marker set. The genome coverage was significantly increased in the map reported here. Implications for quantitative trait loci (QTL) research and marker-assisted breeding perspectives are discussed. Received: 31 August 2000 / Accepted: 16 October 2000     

Detecting and mapping repulsion-phase linkage in polyploids with polysomic inheritance

It has been suggested that ratios of coupling- to repulsion-phase linked markers can be used to distinguish between allopolyploids and autopolyploids, because repulsion-phase linkages are much more difficult to detect in autopolyploids with polysomic inheritance than allopolyploids with disomic inheritance. In this report, we analyze the segregation pattern of repulsion-phase linked markers in polyploids without complete preferential pairing. The observed repulsion-phase recombination fraction (R) in such polyploids is composed of a fraction due to crossing-over (R_c) and another fraction due to independent assortment (R_i). R_i is the minimum distance that can be detected between repulsion-phase linked markers. Because R_i is high in autopolyploids (0.3373, 0.4000, 0.4286 and 0.4444) for autopolyploids of 2n=4x, 6x, 8x and 10x), large population sizes are required to reliably detect repulsion linkages. In addition, the default linkage used in mapping-programs must be greater than the corresponding R_i to determine whether a polyploid is a true autopolyploid. Unfortunately, much lower default linkages than the R_is have been used in recent polyploid studies to determine polyploid type, and markers have been incorporated into polyploid maps based on the R values. Herein, we describe how mapping repulsion linkages can result in spurious results, and present methods to accurately detect the degree of preferential pairing in polyploids using repulsion linkage analysis. Received: 29 February 2000 / Accepted: 17 July 2000     

Molecular scaffold of a new pokeweed antifungal peptide deduced by H nuclear magnetic resonance

The antifungal peptide from seeds of Phytolacca Americana (Pokeweed), designated PAFP-S hereinafter, is a recently found cationic peptide which consists of 38 amino acid residues and exihibites a broad spectrum of antifungal activity, including inhibition of certain saprophytic fungi and some plant pathogens. The secondary structure and three cysteine pairings have been investigated by ¹H NMR analysis. The results show that the molecular scaffold of PAFP-S features a triple-stranded antiparallel β-sheet knotted by a typical disulfide bridge motif, which characterizes the knottin fold. CD spectroscopy indicates a high stability of the molecule in solution. Therefore, PAFP-S should be a new member of the knottin structural family and the first antifungal peptide that adopts the knottin-like fold.     

长芒猬草与华山新麦草属间杂种的形态学和细胞学研究

为研究长芒猬草Hystrix duthiei ssp．longearistata的染色体组成,将其与华山新麦草Psathyrostachys huashanica进行了人工杂交,获得杂种F₁。对亲本及杂种F₁,花粉母细胞减数分裂染色体配对行为、繁育 特性和形态特征进行了比较分析。结果表明：杂种F₁的许多形态特征介于父母本之间,花粉完全不育, 结实率为0;杂种F₁花粉母细胞减数分裂中期Ⅰ染色体配对较高,55.12％的细胞形成5个或6个二价 体,其构型为：9.83Ⅰ+5.46Ⅱ+0.07Ⅲ,C-值为0.57。以上结果表明H．duthiei ssp．Longearistata含有Ns染色体组。本文还讨论了Hystrix与Leymus的关系。     

Evolution of crossover interference enables stable autopolyploidy by ensuring pairwise partner connections in Arabidopsis arenosa

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