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25 April 2020, Volume 42 Issue 02
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  • Articles
    Dramatic impact of metric choice on biogeographical regionalization
    Jian-Fei Ye, Yun Liu, Zhi-Duan Chen
    2020, 42(02):  67-73.  doi:10.1016/j.pld.2019.12.003
    Abstract ( 293 )   HTML ( )   PDF (2665KB) ( 116 )   Save
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    For a quantitative biogeographical regionalization, the choice of an appropriate dissimilarity index to measure pairwise distances is crucial. Several different metrics have been used, but there is no specific study to test the impact of metric choice on biogeographical regionalization. We herein applied a hierarchical cluster analysis on the mean nearest taxon distance (MNTD) and the phylogenetic turnover component of the Sørensen dissimilarity index (pβsim) pairwise distances to generate two schemes of phylogenetic regionalization of the Chinese flora, and then evaluated the effect of metric choice. Floristic regionalization based on MNTD was influenced by richness differences, but regionalization based on pβsim can clearly reflect the evolutionary history of the Chinese flora. We provided a brief description of the five regions identified by pβsim, and the regionalization can help develop strategies to effectively conserve the taxa and floristic regions with different origins and evolutionary histories.
    Crepis desertorum (Asteraceae, Cichorieae), a new species from northern Xinjiang (China) based on morphological and molecular data
    Juan Qiu, Jianwen Zhang, Tiangang Gao, Dunyan Tan
    2020, 42(02):  74-82.  doi:10.1016/j.pld.2019.11.003
    Abstract ( 283 )   HTML ( )   PDF (8055KB) ( 188 )   Save
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    Crepis desertorum from the Junggar Basin of northern Xinjiang, northwestern China, is described as a new species. Molecular studies indicate that the species is closely related to Crepis frigida. Morphological studies indicate that it is similar to Crepis sancta subsp. bifida but differs from the latter taxon in having glandular hairs on the stem, a flat receptacle and dimorphic achenes. Chromosome features and pollen and achene ultrastructure also are described for the new species.
    Spinescent patterns in the flora of Jiaozi Snow Mountain, Southwestern China
    Qi Xu, Simcha Lev-Yadun, Lu Sun, Zhe Chen, Bo Song, Hang Sun
    2020, 42(02):  83-91.  doi:10.1016/j.pld.2019.12.002
    Abstract ( 226 )   HTML ( )   PDF (2236KB) ( 41 )   Save
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    Spinescence has been thought to have evolved mainly as a defense against herbivores. Thus, studying its evolution in a whole flora is an excellent approach for understanding long-term planteherbivore interactions. In this study, we characterized the spinescent plant species of Jiaozi Snow Mountain, Southwestern China, in order to explore the effects of life forms, plant organs, phylogenetic position, and phytogeographical origin on spinescence occurrence. The Jiaozi Snow Mountain flora includes 137 spinescent species (9.2%) out of 1488 angiosperm species. We found that in these spinescent species, vegetative organs (70.0%) were significantly more defended than reproductive organs (43.8%). Life form had a significant effect on spinescence occurrence. Woody species (18.6%) were more likely to be spiny than non-woody species (6.4%); moreover, woody species mostly defend their vegetative organs (92.2%), whereas herbaceous species mostly defend their reproductive organs (73.3%). For woody plants, leaf habit has a significant effect on spinescence. Specifically, spinescence was more common on the reproductive organs of deciduous woody species than on those of evergreen woody species; furthermore, spinescence was more common on the leaf blades of evergreens than on those of deciduous species; however, the proportion of spinescent petioles in deciduous species was significantly higher than in evergreens. The most common spine color was yellow (40.8%), followed by white (16.8%), red (15.8%), and brown (14.3%); furthermore, 74.4% of spinescence that showed aposematic color was a different color than the plant organ on which grown. These findings suggest that spinescence is visually aposematic in the Jiaozi Snow Mountain flora. Phylogenetically, more families tended to have spines on vegetative organs (83.3% in vegetative organs, 50.0% in reproductive organs), but the phylogenetic signals were weak. The proportion of spinescence was not significantly different between tropical (9.8% of genera, 7.6% of species) and temperate (13.2% of genera, 9.5% of species) elements. These results indicate that in the Jiaozi Snow Mountain flora spinescence evolved differently in various life forms and plant organs, but that these differences were not influenced by phylogenetic position or phytogeographical origin.
    Transcriptome Analysis Reveals Clues into leaf-like flower mutant in Chinese orchid Cymbidium ensifolium
    Yonglu Wei, Jianpeng Jin, Xiani Yao, Chuqiao Lu, Genfa Zhu, Fengxi Yang
    2020, 42(02):  92-101.  doi:10.1016/j.pld.2019.12.001
    Abstract ( 213 )   HTML ( )   PDF (8167KB) ( 87 )   Save
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    The floral morphology of Cymbidium ensifolium, a well-known orchid in China, has increasingly attracted horticultural and commercial attention. However, the molecular mechanisms that regulate flower development defects in C. ensifolium mutants are poorly understood. In this work, we examined a domesticated variety of C. ensifolium named ‘CuiYuMuDan’, or leaf-like flower mutant, which lacks typical characteristics of orchid floral organs but continues to produce sepal-to leaf-like structures along the inflorescence. We used comparative transcriptome analysis to identify 6234 genes that are differentially expressed between mutant and wild-type flowers. The majority of these differentially expressed genes are involved in membrane-building, anabolism regulation, and plant hormone signal transduction, implying that in the leaf-like mutant these processes play roles in the development of flower defects. In addition, we identified 152 differentially expressed transcription factors, including the bHLH, MYB, MIKC, and WRKY gene families. Moreover, we found 20 differentially expressed genes that are commonly involved in flower development, including MADS-box genes, CLAVATA3 (CLV3), WUSCHEL (WUS), and PERIANTHIA (PAN). Among them, floral homeotic genes were further investigated by phylogenetic analysis and expression validation, which displayed distinctive spatial expression patterns and significant changes between the wild type and the mutant. This is the first report on the C. ensifolium leaf-like flower mutant transcriptome. Our results shed light on the molecular regulation of orchid flower development, and may improve our understanding of floral patterning regulation and advance molecular breeding of Chinese orchids.
    Analysis of changes in the Panax notoginseng glycerolipidome in response to long-term chilling and heat
    Tao Liu, Jia Chen, Furong Xu, Xiahong He, Shengchao Yang, Youyong Zhu, Weiqi Li, Guowei Zheng
    2020, 42(02):  102-110.  doi:10.1016/j.pld.2019.11.002
    Abstract ( 164 )   HTML ( )   PDF (2876KB) ( 50 )   Save
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    Long-term moderately high or low temperatures can damage economically important plants. In the present study, we treated Panax notoginseng, an important traditional Chinese medicine, with temperatures of 10, 20, and 30℃ for 30 days. We then investigated P. notoginseng glycerolipidome responses to these moderate temperature stresses using an ESI/MS-MS-based lipidomic approach. Both long-term chilling (LTC, 10℃) and long-term heat (LTH, 30℃) decreased photo pigment levels and photosynthetic rate. LTH-induced degradation of photo pigments and glycerolipids may further cause the decline of photosynthesis and thereafter the senescence of leaves. LTC-induced photosynthesis decline is attributed to the degradation of photosynthetic pigments rather than the degradation of chloroplastidic lipids. P. notoginseng has an especially high level of lysophosphatidylglycerol, which may indicate that either P. notoginseng phospholipase A acts in a special manner on phosphatidylglycerol (PG), or that phospholipase B acts. The ratio of sulfoquinovosyldiacylglycerol (SQDG) to PG increased significantly after LTC treatment, which may indicate that SQDG partially substitutes for PG. After LTC treatment, the increase in the degree of unsaturation of plastidic lipids was less than that of extraplastidic lipids, and the increase in the unsaturation of PG was the largest among the ten lipid classes tested. These results indicate that increasing the level of unsaturated PG may play a special role in maintaining the function and stability of P. notoginseng photosystems after LTC treatment.
    Silencing JA hydroxylases in Nicotiana attenuata enhances jasmonic acid-isoleucine-mediated defenses against Spodoptera litura
    Jinxiang Tang, Dahai Yang, Jianqiang Wu, Suiyun Chen, Lei Wang
    2020, 42(02):  111-119.  doi:10.1016/j.pld.2019.11.005
    Abstract ( 153 )   HTML ( )   PDF (1821KB) ( 19 )   Save
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    Jasmonic acid (JA) plays important roles in plant resistance to insect herbivores. One important derivative of JA is 12-OH-JA, which is produced by two independent pathways: direct hydroxylation of JA by jasmonate-induced oxygenases (JOXs) or hydrolyzation of 12-OH-JA-Ile.Yet the function of 12-OH-JA in planteherbivore interactions remains largely unknown. In this study, we silenced four JOX homologs independently in the wild tobacco Nicotiana attenuata by virus-induced gene silencing (VIGS), and found that all four JOX homologs are involved in JA hydroxylation. Simultaneously silencing the four JA hydroxylases in VIGS-NaJOXs plants decreased herbivory-induced 12-OH-JA by 33%, but JA and JA-Ile levels increased by 45% and 30%, respectively, compared to those in control plants. Compared to direct hydroxylation from JA, hydrolyzation from 12-OH-JA-Ile is equally important for herbivory-induced 12-OHJA accumulation: in the 12-OH-JA-Ile deficient irJAR4/6 plants, 12-OH-JA decreased 34%. Moreover, VIGSNaJOXs plants exhibited enhanced resistance to the generalist herbivore Spodoptera litura. The poor larval performance was strongly correlated with high levels of several JA-Ile-dependent direct defense metabolites in the VIGS-NaJOXs plants. When we simultaneously silenced all four JA hydroxylases in the JAIle-deficient irJAR4/6 background, the enhanced herbivore resistance diminished, demonstrating that enhanced herbivore resistance resulted from elevated JA-Ile levels. Given that silencing these NaJOX-like genes did not detectably alter plant growth but highly increased plant defense levels, we propose that JOX genes are potential targets for genetic improvement of herbivore-resistant crops.
    The ubiquity and coexistence of two FBPases in chloroplasts of photosynthetic eukaryotes and its evolutionary and functional implications
    Yujin Li, Qingqing Ye, De He, Huixian Bai, Jianfan Wen
    2020, 42(02):  120-125.  doi:10.1016/j.pld.2019.09.002
    Abstract ( 172 )   HTML ( )   PDF (3314KB) ( 39 )   Save
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    In photosynthetic eukaryotes, there are two well-characterized fructose-1,6-bisphosphatases (FBPases): the redox-insensitive cytosolic FBPase (cyFBPase), which participates in gluconeogenesis, and the redoxsensitive chloroplastic FBPase (cpFBPase1), which is a critical enzyme in the Calvin cycle. Recent studies have identified a new chloroplastic FBPase, cpFBPase2; however, its phylogenetic distribution, evolutionary origin, and physiological function remain unclear. In this study, we identified and characterized these three FBPase isoforms in diverse, representative photosynthetic lineages and analyzed their phylogeny. In contrast to previous hypotheses, we found that cpFBPase2 is ubiquitous in photosynthetic eukaryotes. Additionally, all cpFBPase2s from diverse lineages form a monophyly, suggesting cpFBPase2 is not a recently evolved enzyme restricted to land plants but rather evolved early in the evolution of photosynthetic organisms, and most likely, in the common ancestor of photosynthetic eukaryotes. cyFBPase was probably first duplicated to produce cpFBPase2, and then the latter duplicated to produce cpFBPase1. The ubiquitous coexistence of these two cpFBPases in chloroplasts is most likely the consequence of adaptation to different redox conditions of photosynthesis, especially those caused by recurrent changes in light conditions.