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Mangroves are woody plants that grow at the interface between land and sea in tropical and subtropical latitudes, where they exist in conditions of high salinity, extreme tides, strong winds, high temperatures, and muddy, anaerobic soils. Rhizophoraceae is a key mangrove family, with highly developed morphological and physiological adaptations to extreme conditions. It is an ideal system for the study of the origin and adaptive evolution of mangrove plants. In this study, we characterized and comprehensively compared the transcriptomes of four mangrove species, from all four mangrove genera, as well as their closest terrestrial relative in Rhizophoraceae, using RNA-Seq. We obtained 41,936–48,845 unigenes with N50 values of 982–1,185 bp and 61.42–69.48% annotated for the five species in Rhizophoraceae. Orthology annotations of Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Clusters of Orthologous Groups revealed overall similarities in the transcriptome profiles among the five species, whereas enrichment analysis identified remarkable genomic characteristics that are conserved across the four mangrove species but differ from their terrestrial relative. Based on 1,816 identified orthologs, phylogeny analysis and divergence time estimation revealed a single origin for mangrove species in Rhizophoraceae, which diverged from the terrestrial lineage ~56.4 million years ago (Mya), suggesting that the transgression during the Paleocene–Eocene Thermal Maximum may have been responsible for the entry of the mangrove lineage of Rhizophoraceae into intertidal environments. Evidence showed that the ancestor of Rhizophoraceae may have experienced a whole genome duplication event ~74.6 Mya, which may have increased the adaptability and survival chances of Rhizophoraceae during and following the Cretaceous–Tertiary extinction. The analysis of positive selection identified 10 positively selected genes from the ancestor branch of Rhizophoraceae mangroves, which were mainly associated with stress response, embryo development, and regulation of gene expression. Positive selection of these genes may be crucial for increasing the capability of stress tolerance (i.e., defense against salt and oxidative stress) and development of adaptive traits (i.e., vivipary) of Rhizophoraceae mangroves, and thus plays an important role in their adaptation to the stressful intertidal environments.

Summary Two kinds of green tea were prepared with the young shoots of Camellia kucha and C. ptilophylla, and antioxidative activities of the chemical constituents were determined. Levels of alkaloids, catechins, total polyphenols, flavonoids and amino acids were determined by high‐performance liquid chromatography and UV‐Vis spectrophotometer. Antioxidative activity was evaluated by applying 2,2‐diphenyl‐1‐picrylhydrazyl radical assay and ferric reducing antioxidant power assay. Our results showed that theobromine was the only alkaloid in C. ptilophylla, while there was theacrine in C. kucha, which was coexisting with the caffeine. We confirmed the high content of (−)‐gallocatechin gallate in C. ptilophylla was not the epimerisation of (−)‐epigallocatechin gallate during the heating procedure. These wild teas had higher content of tea polyphenols, water extracts, amion acids and stronger antioxidative activity compared with the longjing tea. They could be used for the development of noncaffeine beverages and new types of tea.

Aim The genus Xylocarpus contains two mangrove species, X. granatum and X. moluccensis, and a rare non‐mangrove, X. rumphii. The two mangrove species are ideal models to study the biogeography of coastal plants with a unique dispersal ability, that is via buoyant propagules. We constructed the phylogeny of Xylocarpus and its relatives and determined the population structures of the two mangrove species. We aimed to elucidate the roles of continental drift and long‐distance dispersal (LDD) in shaping the present‐day distribution of Xylocarpus and to determine the factors affecting the patterns of population differentiation. Location The Indo‐West Pacific (IWP) region. Methods Thirty populations of X. granatum, 15 of X. moluccensis and four of X. rumphii were sampled across the IWP region. Five chloroplast DNA intergenic spacers were sequenced for Xylocarpus and outgroup species to determine divergence times. The genetic diversity, divergence and structure of the two mangrove species were further analysed using five nuclear and two chloroplast DNA loci. Migrations between oceanic regions were estimated. Results The genus Xylocarpus diverged from its sister genus Carapa approximately 19.4 Ma. The populations of X. granatum differentiated into three groups, with genetic breaks present across the Malay Peninsula and Wallacea, whereas X. moluccensis populations differentiated into two groups, with a genetic break present only across the Malay Peninsula. Migration was also observed between populations of the Southeast Asian and Australasian regions in X. moluccensis but not in X. granatum. Main conclusion Since Xylocarpus originated after the breakup of Gondwana and subsequent plate motions, its current distribution range should have been facilitated by present‐day LDD instead of past continental drift. Despite the capacity of LDD, the presence of differing population structures across land barriers (the Sunda and Sahul Shelves) and ocean currents indicated differential limitations in the dispersal capabilities of X. granatum and X. moluccensis.

BackgroundMikania micrantha H.B.K. (Asteraceae) is one of the world’s most invasive weeds which has been rapidly expanding in tropical Asia, including China, while its close relative M. cordata, the only Mikania species native to China, shows no harm to the local ecosystems. These two species are very similar in morphology but differ remarkably in several ecological and physiological traits, representing an ideal system for comparative analysis to investigate the genetic basis underlying invasion success. In this study, we performed RNA-sequencing on the invader M. micrantha and its native congener M. cordata in China, to unravel the genetic basis underlying the strong invasiveness of M. micrantha. For a more robust comparison, another non-invasive congener M. cordifolia was also sequenced and compared.ResultsA total of 52,179, 55,835, and 52,983 unigenes were obtained for M. micrantha, M. cordata, and M. cordifolia, respectively. Phylogenetic analyses and divergence time dating revealed a relatively recent split between M. micrantha and M. cordata, i.e., approximately 4.81 million years ago (MYA), after their divergence with M. cordifolia (8.70 MYA). Gene ontology classifications, pathway assignments and differential expression analysis revealed higher representation or significant up-regulation of genes associated with photosynthesis, energy metabolism, protein modification and stress response in M. micrantha than in M. cordata or M. cordifolia. Analysis of accelerated evolution and positive selection also suggested the importance of these related genes and processes to the adaptability and invasiveness of M. micrantha. Particularly, most (77 out of 112, i.e. 68.75%) positively selected genes found in M. micrantha could be classified into four groups, i.e., energy acquisition and utilization (10 genes), growth and reproduction (13 genes), protection and repair (34 genes), and signal transduction and expression regulation (20 genes), which may have contributed to the high adaptability of M. micrantha to various new environments and the capability to occupy a wider niche, reflected in its high invasiveness.ConclusionsWe characterized the transcriptomes of the invasive species M. micrantha and its non-invasive congeners, M. cordata and M. cordifolia. A comparison of their transcriptomes provided insights into the genetic basis of the high invasiveness of M. micrantha.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4784-9) contains supplementary material, which is available to authorized users.

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BACKGROUND: Kucha (Camellia assamica var. kucha) is a novel wild tea resource grown in China and a tea plant containing a sizable amount of theacrine (1,3,7,9-tetramethyluric acid). High-performance liquid chromatography (HPLC) analysis of purine alkaloids and catechins in young leaves of Kucha has been reported previously. However, the compositions of purine alkaloids and catechins in other parts of the plant remain unknown, and more information about the chemical constituents of Kucha is also necessary for further research and development of this new tea resource.