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Genetic differentiation and phylogeography of partially sympatric species complex Rhizophora mucronata Lam. and R. stylosa Griff. using SSR markers.

ABSTRACT: BACKGROUND:Mangrove forests are ecologically important but globally threatened intertidal plant communities. Effective mangrove conservation requires the determination of species identity, management units, and genetic structure. Here, we investigate the genetic distinctiveness and genetic structure of an iconic but yet taxonomically confusing species complex Rhizophora mucronata and R. stylosa across their distributional range, by employing a suite of 20 informative nuclear SSR markers. RESULTS:Our results demonstrated the general genetic distinctiveness of R. mucronata and R. stylosa, and potential hybridization or introgression between them. We investigated the population genetics of each species without the putative hybrids, and found strong genetic structure between oceanic regions in both R. mucronata and R. stylosa. In R. mucronata, a strong divergence was detected between populations from the Indian Ocean region (Indian Ocean and Andaman Sea) and the Pacific Ocean region (Malacca Strait, South China Sea and Northwest Pacific Ocean). In R. stylosa, the genetic break was located more eastward, between populations from South and East China Sea and populations from the Southwest Pacific Ocean. The location of these genetic breaks coincided with the boundaries of oceanic currents, thus suggesting that oceanic circulation patterns might have acted as a cryptic barrier to gene flow. CONCLUSIONS:Our findings have important implications on the conservation of mangroves, especially relating to replanting efforts and the definition of evolutionary significant units in Rhizophora species. We outlined the genetic structure and identified geographical areas that require further investigations for both R. mucronata and R. stylosa. These results serve as the foundation for the conservation genetics of R. mucronata and R. stylosa and highlighted the need to recognize the genetic distinctiveness of closely-related species, determine their respective genetic structure, and avoid artificially promoting hybridization in mangrove restoration programmes.

SUBMITTER: Wee AK

PROVIDER: S-EPMC4389924 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Project description:Mangrove endophytic fungi are tolerant to numerous stresses and are inevitably capable of exhibiting excellent biological activity by producing impressive numbers of metabolites with special biological functions, based on previous work on the biological potential of mangrove-derived endophytic fungi. To obtain marked antimicrobial and cytotoxic fermentation products of culturable endophytic fungi from mangrove forests, our research evaluated the antimicrobial and cytotoxic activities of crude extracts of endophytic fungi from Rhizophora stylosa and Rhizophora mucronata. Forty-six fungal isolates were cultured on four different media, namely, dextrose agar (PDA), Czapek's agar (CZA), rice medium (RM) and grain medium (GM) and harvested by ethyl acetate solvent at 40 days. The extracts were tested for antimicrobial activity by the microdilution method against the gram-negative bacteria Pseudomonas adaceae (PA), gram-positive bacteria Enterococcus faecalis (EF), methicillin-resistant Staphylococcus aureus (MRSA) and pathogenic fungus Monilia albicans (MA). The cytotoxic activity of the extracts was evaluated by MTT assay using A549 human lung cancer cells, HeLa human cervical carcinoma cells, and HepG2 human hepatocellular cells. The results showed that rice medium could promote the secretion of antimicrobial and antitumour secondary metabolites of endophytic fungi in comparison with other cultivation media. Seventeen strains (68%) from R. stylosa exhibited inhibitory effects on indicators, especially N. protearum HHL46, which could inhibit the growth of four microbes with MIC values reaching 0.0625 mg/mL. Fifteen strains (71.4%) from R. mucronata displayed activities against human pathogenic microbes; in particular, Pestalotiopsis sp. HQD6 and N. protearum HQD5 could resist the growth of four microbes with MIC values ranging from 0.015 to 1 mg/mL. In the cytotoxicity assay, the extracts of 10 strains (40%), 9 strains (40%) and 13 strains (52%) of R. stylosa and 13 strains (61.9%), 10 strains (47.6%) and 10 strains (47.6%) of R. mucronata displayed cytotoxicity against A549, HeLa and HepG2 cancer cells with cell viability values ≤ 50%. Neopestalotiopsis protearum HHL46, Phomopsis longicolla HHL50, Botryosphaeria fusispora HQD83, Fusarium verticillioides HQD48 and Pestalotiopsis sp. HQD6 displayed significant antitumour activity with IC50 values below 20 μg/mL. These results highlighted the antimicrobial and antitumour potential of endophytic fungi from R. stylosa and R. mucronata and the possibility of exploiting their antimicrobial and cytotoxic agents.

Project description:Currently, there is a renewed interest towards the development of plant-based pharmacophores. In this work, 16 extracts prepared from the leaves, twigs, roots and fruits of a hydro-halophyte, Rhizophora mucronata Lam. (Family: Rhizophoraceae), were studied for possible antioxidant activity and the phenolic profiles established. Thereafter, enzymatic inhibitory activities (?-amylase, ?-glucosidase, tyrosinase, acetyl- (AChE), butyrylcholinesterase (BChE), lipase, and elastase) were assessed. The total phenolic, flavonoid, phenolic acid, tannin, flavanol and triterpenoid content were estimated using standard assays. An untargeted metabolomics-based approach, based on ultra-high-pressure liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPLC-QTOF-MS) followed by multivariate statistics, was then used to comprehensively profile and describe the phenolics present. UHPLC-QTOF-MS allowed for putatively annotating 104 phenolic acids, 103 flavonols, 94 flavones, 71 anthocyanins, 66 tyrosols, 29 lignans, 15 alkylphenols and 10 stilbenes in the extracts. Nine strains (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Methicillin-resistant Staphylococcus aureus (MRSA), Salmonella enteritidis, Sarcina lutea, Proteus mirabilis, Bacillus cereus and Candida albicans) were then used to investigate the antimicrobial properties. The methanolic twig extract exhibited significant reducing potential towards Cu (II)/Cu (I) and Fe (III)/Fe (II) (1336.88 ± 15.70 and 710.18 ± 21.04 mg TE/g, respectively) and was the most potent DPPH radical scavenger (807.07 ± 6.83 mg TE/g). Additionally, the methanolic twig extract showed significant inhibition against most targeted enzymes. Anti-microbial results showed that all extracts were active against MRSA. Multivariate analysis demonstrated that the phenolic profile of ethyl acetate extracts and leaves were the two most discriminative parameters in terms of solvents and organs, respectively. The present findings indicated that R. mucronata may be further explored for the management/prevention of oxidative stress, neurodegenerative complications and hyperpigmentation.

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Genetic differentiation and phylogeography of partially sympatric species complex Rhizophora mucronata Lam. and R. stylosa Griff. using SSR markers.

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