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25 June 2016, Volume 38 Issue 03
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  • Articles
    New fossil seeds of Eurya (Theaceae) from East Asia and theirpaleobiogeographic implications
    Hai Zhu a, c, Yong-Jiang Huang a, d, **, Tao Su b, Zhe-Kun Zhou a, b, *
    2016, 38(03):  125.  doi:
    Abstract ( 268 )   HTML ( )   PDF (10786KB) ( 235 )   Save
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    Eurya has an excellent fossil record in Europe, but it has only a few fossil occurrences in East Asia though this vast area houses the highest modern diversity of the genus. In this study, three-dimensionally preserved fossil seeds of Eurya stigmosa (Ludwig) Mai from the late Pliocene of northwestern Yunnan, southwestern China are described. The seeds are compressed and flattened, slightly campylotropous, and nearly circular to slightly angular in shape. The surface of the seeds is sculptured by a distinctive foveolate pattern, consisting of funnel-shaped and finely pitted cells. Each seed valve contains a reniform or horseshoe-shaped embryo cavity, a characteristic condyle structure and an internal raphe. These fossil seeds represent one of the few fossil records of Eurya in East Asia. This new finding therefore largely extends the distributional ranges of Eurya during Neogene. Fossil records summarized here show that Eurya persisted in Europe until the early Pleistocene, but disappeared thereafter. The genus might have first appeared in East Asia no later than the late Oligocene, and dispersed widely in regions such as Japan, Nepal, and southwestern China.

    Latitudinal trends in genus richness of vascular plants in the Eocene and Oligocene of North America
    AJ. Harris a, *, Cassondra Walker b, Justin R. Dee c, Michael W. Palmer d
    2016, 38(03):  133-141.  doi:
    Abstract ( 209 )   HTML ( )   PDF (2840KB) ( 232 )   Save
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    The latitudinal richness gradient is a frequent topic of study on the modern landscape, but its history in deep time is much less well known. Here, we preliminarily evaluated the paleolatitudinal richness gradient of vascular plants for the Eocene (56-33.9 million years ago) and Oligocene (33.9-23 million years ago) epochs of North America north of Mexico using 201 fossil floras. We calculated the direction and shape of the gradient using quadratic regression to detect linear and curvilinear trends. We performed regressions for the Eocene and Oligocene as well as for informal time intervals within the Eocene: early, middle, and middle þ late. We found that quadratic models better explain the data than linear models for both epochs as well as for the early Eocene. A roughly linear trend in the middle and middle þ late intervals may reflect limited sampling of high latitude floras for those times. The curvilinear relationship was weak for the Eocene and the model showed a peak in richness at 45.5N. The curvilinear relationship was much stronger for the Oligocene and the peak occurred at 48.5N. In the Eocene, the mid-latitude peak in richness may be explained by mean annual temperature, which was probably higher at some mid-latitudes than at lower ones. For the Oligocene, the peak in richness at midlatitudes may be explained by evolutionary diversification within the temperate zone or by increased aridity at low latitudes. We also assessed the latitudinal richness gradient of genera within modern floras in North America north of Mexico and we found a weak, curvilinear trend with a peak in richness at 31.5N. Our results suggest that the latitudinal genus richness gradient of vascular plants in North America continued to develop into its modern structure following the Oligocene.

    The rapid climate change-caused dichotomy on subtropical evergreen broad-leaved forest in Yunnan: Reduction in habitat diversity and increase in species diversity
    Zhe Ren a, b, Hua Peng a, *, Zhen-Wen Liu a, **
    2016, 38(03):  142-148.  doi:
    Abstract ( 227 )   HTML ( )   PDF (6397KB) ( 400 )   Save
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    Yunnan's biodiversity is under considerable pressure and subtropical evergreen broad-leaved forests in this area have become increasingly fragmented through agriculture, logging, planting of economic plants, mining activities and changing environment. The aims of the study are to investigate climate changeinduced changes of subtropical evergreen broad-leaved forests in Yunnan and identify areas of current species richness centers for conservation preparation. Stacked species distribution models were created to generate ensemble forecasting of species distributions, alpha diversity and beta diversity for Yunnan's subtropical evergreen broad-leaved forests in both current and future climate scenarios. Under stacked species distribution models in rapid climate changes scenarios, changes of water-energy dynamics may possibly reduce beta diversity and increase alpha diversity. This point provides insight for future conservation of evergreen broad-leaved forest in Yunnan, highlighting the need to fully consider the problem of vegetation homogenization caused by transformation of water-energy dynamics.

    An acyltransferase gene that putatively functions in anthocyanin modification was horizontally transferred from Fabaceae into the genus Cuscuta
    Ting Sun a, b, , Yuxing Xu a, b, , Dale Zhang c, Huifu Zhuang a, b, Jianqiang
    2016, 38(03):  149-155.  doi:
    Abstract ( 225 )   HTML ( )   PDF (11180KB) ( 220 )   Save
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    Horizontal gene transfer (HGT) refers to the flow of genetic materials to non-offspring, and occasionally HGT in plants can improve the adaptation of organisms in new niches due to expanded metabolic capability. Anthocyanins are an important group of water-soluble red, purple, or blue secondary metabolites, whose diversity results from modification after the main skeleton biosynthesis. Cuscuta is a stem holoparasitic genus, whose members form direct connection with hosts to withdraw water, nutrients, and macromolecules. Such intimate association is thought to increase the frequency of HGT. By transcriptome screening for foreign genes in Cuscuta australis, we discovered that one gene encoding a
    putative anthocyanin acyltransferase gene of the BAHD family, which is likely to be involved in anthocyanin modification, was acquired by C. australis from Fabaceae through HGT. The anthocyanin acyltransferase-like (AT-like) gene was confirmed to be present in the genome assembly of C. australis and the transcriptomes of Cuscuta pentagona. The higher transcriptional level in old stems is consistent with its putative function in secondary metabolism by stabilizing anthocyanin at neutral pH and thus HGT of this AT-like gene may have improved biotic and abiotic resistance of Cuscuta.

    Submergence induced changes of molecular species in membrane lipids in Arabidopsis thaliana
    Mulan Wang a, b, , Yunmei Shen c, , Faqing Tao b, Shengchao Yang a, Weiqi Li b
    2016, 38(03):  156-162.  doi:
    Abstract ( 222 )   HTML ( )   PDF (10888KB) ( 205 )   Save
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    The composition of membrane lipids is sensitive to environmental stresses. Submergence is a type of stress often encountered by plants. However, how the molecular species of membrane lipids respond to submergence has not yet been characterised. In this study, we used a lipidomic approach to profile the molecular species of membrane lipids in whole plants of Arabidopsis thaliana that were completely submerged for three days. The plants survived one day of submergence, after which, we found that the total membrane lipids were only subtly decreased, showing significant decreases of monogalactosyldiacylglycerol (MGDG) and phosphatidylcholine (PC) and an increase of phosphatidic acid (PA);
    however, the basic lipid composition was retained. In contrast, three days of submergence caused plants to die, and the membranes deteriorated via the rapid loss of 96% of lipid content together with a 229% increase in PA. The turnover of molecular species from PG and MGDG to PA indicated that submergenceinduced lipid changes occurred through PA-mediated degradation. In addition, molecular species of extraplastidic PG degraded sooner than plastidic ones, lyso-phospholipids exhibited various patterns of change, and the double-bond index (DBI) remained unchanged until membrane deterioration. Our results revealed the unique changes of membrane lipids upon submergence and suggested that the major cause of the massive lipid degradation could be anoxia.

    RNA-seq analysis of Paris polyphylla var. yunnanensis roots identified candidate genes for saponin synthesis
    Tao Liu a, Xiaoxian Li b, Shiqing Xie a, Ling Wang a, Shengchao Yang a, *
    2016, 38(03):  163-170.  doi:
    Abstract ( 213 )   HTML ( )   PDF (4662KB) ( 280 )   Save
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    Paris polyphylla Smith var. yunnanensis (Franch.) Hand.-Mazz. is a rhizomatous, herbaceous, perennial plant that has been used for more than a thousand years in traditional Chinese medicine. It is facing extinction due to overharvesting. Steroids are the major therapeutic components in Paris roots, the commercial value of which increases with age. To date, no genomic data on the species have been available. In this study, transcriptome analysis of an 8-year-old root and a 4-year-old root provided insight into the metabolic pathways that generate the steroids. Using Illumina sequencing technology, we generated a high-quality sequence and demonstrated de novo assembly and annotation of genes in the absence of prior genome information. Approximately 87,577 unique sequences, with an average length of 614 bases, were obtained from the root cells. Using bioinformatics methods, we annotated approximately 65.51% of the unique sequences by conducting a similarity search with known genes in the National Center for Biotechnology Information's non-redundant database. The unique transcripts were functionally classified using the Gene Ontology hierarchy and the Kyoto Encyclopedia of Genes and Genomes database. Of 3082 genes that were identified as significantly differentially expressed between roots of different ages, 1518 (49.25%) were upregulated and 1564 (50.75%) were downregulated in the older root. Metabolic pathway analysis predicted that 25 unigenes were responsible for the biosynthesis of the saponins steroids. These data represent a valuable resource for future genomic studies on this endangered species and will be valuable for efforts to genetically engineer P. polyphylla and facilitate saponin-rich plant development.