25 December 2018, Volume 40 Issue 06

    

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  New insights into the phylogeny and infrageneric taxonomy of Saussurea based on hybrid capture phylogenomics (Hyb-Seq)

  Liansheng Xu, Zhuqiu Song, Tian Li, Zichao Jin, Buyun Zhang, Siyi Du, Shuyuan Liao, Xingjie Zhong, Yousheng Chen

  Plant Diversity. 2018, 40(06): 1-2. https://doi.org/doi.org/10.1016/j.pld.2024.10.003

  Abstract ( 710) Download PDF ( 295 ) PDF Mobile ( 0 ) HTML   Knowledge map   Save

  Saussurea is one of the largest and most rapidly evolving genera within the Asteraceae, comprising approximately 520 species from the Northern Hemisphere. A comprehensive infrageneric classification, supported by robust phylogenetic trees and corroborated by morphological and other data, has not yet been published. For the first time, we recovered a well-resolved nuclear phylogeny of Saussurea consisting of four main clades, which was also supported by morphological data. Our analyses show that ancient hybridization is the most likely source of deep cytoplasmic-nuclear conflict in Saussurea, and a phylogeny based on nuclear data is more suitable than one based on chloroplast data for exploring the infrageneric classification of Saussurea. Based on the nuclear phylogeny obtained and morphological characters, we proposed a revised infrageneric taxonomy of Saussurea, which includes four subgenera and 13 sections. Specifically, 1) S. sect. Cincta, S. sect. Gymnocline, S. sect. Lagurostemon, and S. sect. Strictae were moved from S. subg. Saussurea to S. subg. Amphilaena, 2) S. sect. Pseudoeriocoryne was moved from S. subg. Eriocoryne to S. subg. Amphilaena, and 3) S. sect. Laguranthera was moved from S. subg. Saussurea to S. subg. Theodorea.
  
  
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  Generation and classification of transcriptomes in two Croomia species and molecular evolution of CYC/TB1 genes in Stemonaceae

  Ruisen Lu, Wuqin Xu, Qixiang Lu, Pan Li, Jocelyn Losh, Faiza Hina, Enxiang Li, Yingxiong Qiu

  Plant Diversity. 2018, 40(06): 253-264. https://doi.org/10.1016/j.pld.2018.11.006

  Abstract ( 757) Download PDF ( 453 ) HTML   Knowledge map   Save

  The genus Croomia (Stemonaceae) is an excellent model for studying the evolution of the Eastern Asia (EA) eEastern North America (ENA) floristic disjunction and the genetic mechanisms of floral zygomorphy formation. In addition to the presence of both actinomorphic and zygomorphic flowers within the genus, species are disjunctively distributed between EA and ENA. However, due to the limited availability of genomic resources, few studies of Croomia have examined these questions. In this study, we sequenced the floral and leaf transcriptomes of the zygomorphic flowered Croomia heterosepala and the actinomorphic flowered Croomia japonica, and used comparative genomic approaches to investigate the transcriptome evolution of the two closely related species. The sequencing and de novo assembly of transcriptomes from flowers of C. heterosepala (ChFlower), flowers of C. japonica (CjFlower), and leaves of C. japonica (CjLeaf) yielded 57,193, 62,131 and 64,448 unigenes, respectively. In addition, estimation of Ka/Ks ratios for 11,566 potential orthologous groups between ChFlower and CjFlower revealed that only six pairs had Ka/Ks ratios significantly greater than 1 and are likely under positive selection. A total of 429 single copy nuclear genes (SCNGs) and 21,460 expression sequence tags-simple sequence repeats (ESTSSRs) were identified in this study. Specifically, we identified seven CYC/TB1-like genes from Stemonaceae. Phylogenetic and molecular evolution analyses indicated that these CYC/TB1-like genes formed a monophyletic clade (SteTBL1) and were subject to strong purifying selection. The shifts of floral symmetry in Stemonaceae do not appear to be correlated with TBL copy number.
  
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  Factors limiting the recruitment of Quercus schottkyana, a dominant evergreen oak in SW China

  Ke Xia, Roy Turkington, Hong-yu Tan, Lei Fan

  Plant Diversity. 2018, 40(06): 277-283. https://doi.org/10.1016/j.pld.2018.11.004

  Abstract ( 353) Download PDF ( 102 ) HTML   Knowledge map   Save

  Quercus schottkyana is a dominant species of oak in the Asian evergreen broad-leaved forests in southwestern China but seedlings are uncommon and recruitment is rare. Annual acorn production by Q. schottkyana is variable and the acorns are exposed to a series of mortality risks. Understanding the factors that limit recruitment of the oak requires knowledge of the oak's life cycle from acorn production to germination and seedling establishment. In this study, we first tested the effects of acorn density on establishment of seedlings by placing batches of acorns at different densities throughout the study area. Second, we tested the effects of herbivores on seedling survival by erecting fences around both natural and transplanted seedling populations. Our results show that even though the rate of seedling establishment increases as acorn density increases (for 32-8000 acorns·m^-2), survival rates of seedlings in the field were generally low (0-0.6%). We show that seedling recruitment of Q. schottkyana is mainly limited to the acorn stage where 88% of the acorns died from the combined effects of desiccation and predation by weevils (Curculio) and bark beetles (Coccotrypes sp.). Herbivory results in the death of some seedlings and consequently also affects the recruitment of seedlings of Q. schottkyana.
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  Morphological plasticity and adaptation level of distylous Primula nivalis in a heterogeneous alpine environment

  Aysajan Abdusalam, Qingjun Li

  Plant Diversity. 2018, 40(06): 284-291. https://doi.org/10.1016/j.pld.2018.11.003

  Abstract ( 382) Download PDF ( 103 ) HTML   Knowledge map   Save

  Plant populations at high elevation face extreme climatic conditions and resource limitations. The existence of distylous species at different elevations can help us investigate their adaptation to high altitudes, the evolution of their morphological characteristics, as well as their responses to limited resources. Here, 17 populations of Primula nivalis at different elevations were evaluated regarding variations in plant morphological characteristics, biomass allocation, and morphological plasticity in a heterogeneous environment. Our results demonstrate that heterogeneous environments can affect plant morphological characteristics and resource allocation in each sexual morph of these plants. Moreover, environmental variations reduced morphological plasticity in the two plant morphs, and the plasticity of long style (LS) plants was greater than that of short style (SS) plants. There were significant negative correlations between morphological characteristics and elevation, rainfall, temperature, and sunshine, and these are the main variables that affect morphological characteristics and resource allocation of both morphs of P. nivalis plants in heterogeneous environments. The morphological characteristics of P. nivalis plants transplanted from high to lower elevations were not significantly different in either population. LS plants had greater morphological plasticity and adaptability in heterogeneous environments than SS plants. Elevational gradients and heterogeneous environments differentiated both morphs of P. nivalis plants with regards to morphology as well as adaptations. LS plants showed a higher level of adaptability than SS plants.
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  Phospholipase D antagonist 1-butanol inhibited the mobilization of triacylglycerol during seed germination in Arabidopsis

  Yanxia Jia, Weiqi Li

  Plant Diversity. 2018, 40(06): 292-298. https://doi.org/10.1016/j.pld.2018.11.002

  Abstract ( 314) Download PDF ( 100 ) HTML   Knowledge map   Save

  Storage oil breakdown plays an important role in the life cycle of many plants by providing the carbon skeletons that support seedling growth immediately following germination. 1-Butanol, a specific inhibitor of phospholipase D (PLD)-dependent production of the signalling molecule phosphatidic acid (PA), inhibited Arabidopsis seed germination. N-Acylethanolamines (NAEs), which have been shown to inhibits PLDα1 activity, have no effect on seed germination. However, mobilization profile of triacylglycerols (TAG) that induced by each compound has not been reported. To gain deeper insights into the mode of mobilization of TAG during NAE 12:0 or 1-butanol treatment, we conducted a detailed comparative analysis of the effect of NAE 12:0, DMSO, 1-butanol and tert-butanol on Arabidopsis seed germination and fatty acid composition, tert-butanol and DMSO served as the corresponding controls treatment respectively. Our data show that 1-butanol, but not the inactive tert-butanol isomer, inhibited Arabidopsis seed germination, which is accompanied by a with retardation of the mobilization of triacylglycerols (TAG). In contrast, NAE 12:0 did not affect mobilization of TAG, nor did it significantly delay seed germination as monitored by radicle and cotyledon emergence. 1-Butanol induced RNA degradation in seeds and seedlings. We speculate that the large-scale degradation of RNA under the induction of 1-butanol may lead to abnormal gene expression in genes necessary for seed germination, including the genes needed for the mobilization of oil bodies, and thus cause a delay of seed germination. To the best of our knowledge, we report for the first time that 1-butanol delays the mobilization of TAG.