Genetic structure of Mesoamerican populations of Big-leaf mahogany (Swietenia macrophylla) inferred from microsatellite analysis

While microsatellites have been used to examine genetic structure in local populations of Neotropical trees, genetic studies based on such high-resolution markers have not been carried out for Mesoamerica as a whole. Here we assess the genetic structure of the Mesoamerican mahogany Swietenia macrophylla King (big-leaf mahogany), a Neotropical tree species recently listed as endangered in CITES which is commercially extinct through much of its native range. We used seven variable microsatellite loci to assess genetic diversity and population structure in eight naturally established mahogany populations from six Mesoamerican countries. Measures of genetic differentiation (FST and RST) indicated significant differences between most populations. Unrooted dendrograms based on genetic distances between populations provide evidence of strong phylogeographic structure in Mesoamerican mahogany. The two populations on the Pacific coasts of Costa Rica and Panama were genetically distant from all the others, and from one another. The remaining populations formed two clusters, one comprised of the northern populations of Mexico, Belize and Guatemala and the other containing the southern Atlantic populations of Nicaragua and Costa Rica. Significant correlation was found between geographical distance and all pairwise measures of genetic divergence, suggesting the importance of regional biogeography and isolation by distance in Mesoamerican mahogany. The results of this study demonstrate greater phylogeographic structure than has been found across Amazon basin S. macrophylla. Our findings suggest a relatively complex Mesoamerican biogeographic history and lead to the prediction that other Central American trees will show similar patterns of regional differentiation.     

Population genetic structure of mahogany (Swietenia macrophylla King, Meliaceae) across the Brazilian Amazon, based on variation at microsatellite loci: implications for conservation

Mahogany (Swietenia macrophylla, Meliaceae) is the most valuable and intensively exploited Neotropical tree. No information is available regarding the genetic structure of mahogany in South America, yet the region harbours most of the unlogged populations of this prized hardwood. Here we report on the genetic diversity within and the differentiation among seven natural populations separated by up to 2100 km along the southern arc of the Brazilian Amazon basin. We analysed the variation at eight microsatellite loci for 194 adult individuals. All loci were highly variable, with the number of alleles per locus ranging from 13 to 27 (mean = 18.4). High levels of genetic diversity were found for all populations at the eight loci (mean HE = 0.781, range 0.754-0.812). We found moderate but statistically significant genetic differentiation among populations considering both estimators of FST and RST, theta = 0.097 and rho = 0.147, respectively. Estimates of theta and rho were significantly greater than zero for all pairwise population comparisons. Pairwise rho-values were positively and significantly correlated with geographical distance under the isolation-by-distance model. Furthermore, four of the populations exhibited a significant inbreeding coefficient. The finding of local differentiation among Amazonian mahogany populations underscores the need for in situ conservation of multiple populations of S. macrophylla across its distribution in the Brazilian Amazon. In addition, the occurrence of microgeographical genetic differentiation at a local scale indicates the importance of maintaining populations in their diverse habitats, especially in areas with mosaics of topography and soil.     

A TAXONOMIC STUDY OF THE GENUS PADINA (DICTYOTALES,PHAEOPHYCEAE) INCLUDING THE DESCRIPTIONS OF FOUR NEW SPECIES FROM JAPAN,HAWAII, AND THE ANDAMAN SEA1

A taxonomic study of the genus Padina from Japan, Southeast Asia, and Hawaii based on morphology and gene sequence data (rbcL and cox3) resulted in the recognition of four new species, that is, Padina macrophylla and Padina ishigakiensis from Ryukyu Islands, Japan; Padina maroensis from Hawaii; and Padina usoehtunii from Myanmar and Thailand. All species are bistratose and morphologically different from one another as well as from any known taxa by a combination of characters relating to degree of calcification; the structure, position, and arrangement of hairlines (HLs) and reproductive sori; and the presence or absence of rhizoid‐like groups of hairs and an indusium. Molecular phylogenetic analyses demonstrated a close relationship between P. ishigakiensis, P. macrophylla, P. maroensis, and Padina australis Hauck. The position of P. usoehtunii, however, was not fully resolved, being either sister to a clade comprising the other three new species and P. australis in the rbcL tree or more closely related to a clade comprising several other recently described species in the cox3 tree. The finding of the four new species demonstrates high species diversity particularly in southern Japan. The following characters were first recognized here to be useful for species delimitation: the presence or absence of small rhizoid‐like groups of hairs on the thallus surface, structure and arrangement of HLs on both surfaces either alternate or irregular, and arrangement of the alternating HLs between both surfaces in equal or unequal distance. The evolutionary trajectory of these and six other morphological characters used in species delineation was traced on the phylogenetic tree.     

大叶碎米荠营养成分的研究

对大叶碎米荠的营养成分进行了详细的分析。结果表明,大叶碎米荠含有丰富的蛋白质、膳食纤维、氨基酸、矿物质和多种维生索,重金属含量远低于国家限量指标,是一种值得开发的绿色野生植物资源。     

马桑绣球(绣球科)的花器官发生和发育

在扫描电镜下观察了马桑绣球Hydrangea aspera孕性花的发生及发育过程。马桑绣球的花器官向心轮状发生：花萼原基以2/5螺旋式相继发生,花瓣原基几乎同步发生。花瓣开始发育时,与花萼相对的雄蕊发生。与花瓣相对的雄蕊原基与心皮原基几乎同时出现。初始心皮向上扩展,分化出花柱和柱头,向下延伸,嵌入花托,发育为下位子房。花发育成熟时,隔膜于子房的下部连续,而中部和上部不连续,即子房为不完全2室。经过与绣球属已观察过的另外5种1亚种花器官发生和发育比较,发现马桑绣球与藤绣球H. ano mala subs     

Distribution of Trans zeatin,GA7/4, (+)ABA and IAA in Tobacco Egg Cells Before and After Fertilization: Immunogold Electron Microscopic Observations

Changes in distribution of trans-zeatin (t-Z), gibberellin A7 and A4(GA7/4), ( + )abscisic acid [( + )ABA] and indoleacetic acid (IAA) in the egg cells of Nicotiana tabacum var. macrophylla before and after fertilization were studied with immunoelectron microscopy. The ovules just at pollination or 96 h after pollination were fixed with 2% EDC [ 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide] and then with the mixed paraformaldehyde and glutaraldehyde for acidic phytohormones (or only with the aldehydes for t-Z), then slightly posffixed in 0.5% OsO4 solution for 30 min. After etched in 1% H2O2 for 10 min, the ultrathin sections embedded in Epon 812 resin were immunostained with rabbit anti-t-Z (and t-ZR) polyclonal antibody (PAB), anti-lAA methyl ester PAb, mouse anti-GA7 and GA4 methyl esters monoclonal antibody(MAb), or anti-( + ) ABA methyl ester MAb, respectively. Protein A- or sheep anti-mouse IgG-colloidal gold (Φ 10 nm) were used to indicate rabbit PAbs or mouse MAbs respectively. In the model system of nitrocellulose membrane via immunogold-silver enhancement, the authors ascertained that immunostaining results at the basis of 1 ng per phytohonnone (t-Z, IAA, GA4, or ( + )ABA) were comparable among the four-kind phytohormones and that t-Z riboside was far less fixed than t-Z with aldehydes. So the anti-t-Z PAb mainly recognized t-Z in aldehyde-fixed tissues. Immunogold electron microscopic observations showed that t-Z was rich in the egg cells before fertilization. In contrast the amounts of GA7/4 and ( + )ABA were lower in egg cells before fertilization but slightly increased after fertilization. Less IAA in egg cells was found either before or after fertilization, t-Z in unfertilized egg cells appeared to concentrate on the nucleus, endoplasmic reticulnm and mitochondria, t-Z is rarely observed in the nuclei of synergids before fertilization but is abundant in the chalazal end of synergids and micropylar end of the central cell adjacent to the unfertilized egg cell. After fertilization, t-Z decreased bviously in the zygotes and the persistent synergids, but appeared in the thickened walls of the zygotes.     

绣球‘杜丽'AP3基因克隆与基因编辑载体构建

绣球(Hydrangea macrophylla)是以花序为主要观赏部位的园林植物,多用作切花装饰和景观营造,在亚洲、美洲、欧洲广泛栽培。为探究AP3基因在绣球花萼形成过程中的功能,加快重瓣绣球新品种培育进程,该研究以绣球‘杜丽''为材料,克隆其MADS-box B类基因HmAP3,并结合生物信息学方法预测基因功能; 根据HmAP3序列信息,筛选出高特异性编辑靶点并构建CRISPR/Cas9基因编辑载体,通过农杆菌转化法将载体整合到绣球基因组中。结果表明:(1)克隆到1段HmAP3基因的cDNA序列,其序列全长546 bp,共编码181个氨基酸,测序结果表明其氨基酸序列与参考序列一致性为100%,与拟南芥AtAP3相似度为58.8%。(2)不同属植物AP3氨基酸序列差异较大,在同属不同物种中,AP3蛋白主要结构较为保守,仅在少数基序上存在差异。(3)在HmAP3中共鉴定到2个高特异性靶点,并成功构建2个单靶点CRISPR/Cas9基因编辑载体。(4)该研究共获得5株基因组内含有Cas9序列的抗性芽,但其靶点均未突变,在抗性芽中没有检测到Cas9表达。该研究探讨了AP3基因在重瓣绣球育种中的价值,对绣球的CRISPR/Cas9基因编辑技术进行了初探,为绣球优良品种繁育工作奠定了基础。     

大叶盘果菊化学成分的研究

采用乙醇提取,硅胶柱层析分离和波谱方法鉴定结构,从大叶盘果菊(Prenanthes macrophylla Franch)中初步分离鉴定出8个化合物:木栓酮(friedelin,1)、木栓醇(friedelanol,2)、α-香树脂醇(α-amyrin,3)、α-香树脂醇乙酸脂(α-amyrin acetate,4)、β-香树脂醇乙酸酯(β-amyrin acetate,5)、蒲公英甾醇乙酸酯(taraxasteryl acetate,6)、β-谷甾醇(β-sitosterol,7)、二十八烷酸(octacosanoic acid,8),这些化合物均为首次从该植物中分离得到。     

中国绣球属植物的修订

中国绣球属植物的修订卫兆芬（中国科学院华南植物研究所,广州５１０６５０）ＡＲＥＶＬＳＩＯＮＯＦＴＨＥＧＥＮＵＳＨＹＤＲＡＮＧＥＡＩＭＣＨＩＮＡ￥ＷｅｉＣｈａｏｆｅｎ（ＳｏｕｔｈＣｈｉｎａＩｎｓｔｉｔｕｔｅｏｆＢｏｔａｎｙ,ＡｃａｄｅｍｉａＳｉｎｉｃａ...