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The present study was aimed at evaluating the antidiabetic activity of the ethanol bark extract of a mangrove plant Avicennia officinalis (AOEB) in streptozotocin (STZ)-induced diabetic mice. The study revealed AOEB could lower the blood glucose level significantly (p <.05) in diabetic mice at dose of 200 mg/kg b.w. The elevated total cholesterol, triglyceride, liver toxicity makers (SGOT and SGPT) and urea level were found to be ameliorated. The in vitro bioactivity-guided assay of AOEB led to isolation of a bioactive compound that inhibits the carbohydrate metabolizing enzymes (α-amylase and α-glucosidase) and also scavenging the DPPH, ABTS and superoxide radicals. The structure of the isolated compound was analyzed by different spectral techniques as FT-IR, CHNS, 1H NMR, 13C NMR, MS. Further, the isolated compound was analyzed by HPLC. However, further studies are required to elucidate the exact structure of the isolated compound. • In vivo antidiabetic study of A. officinalis bark extract was carried out. • GC‐MS analysis was carried out to characterize bioactive principles. • Bioactivity guided study was carried out to isolate the active compound. [ABSTRACT FROM AUTHOR]

Salinity reduces the growth and productivity of crop plants worldwide. Mangroves have evolved efficient ion homeostasis mechanisms to survive under their natural saline growth habitat. Information obtained from them may be utilized for increasing the salt tolerance of crop plants. We identified and characterized a high-affinity potassium transporter gene (AoHKT1) from Avicennia officinalis. The expression of AoHKT1 was induced by NaCl mainly in the leaves. Functional study by heterologous expression of AoHKT1 in Arabidopsis T-DNA insertional mutants athkt1–1 and athkt1–4 revealed that it could enhance the salt tolerance of the mutant plants. This was accompanied by an increase in K+ accumulation in the leaves. AoHKT1 was localized to the plasma membrane in Arabidopsis, and when expressed in yeast, it could complement the functions of both Na+ and K+ transporters. An attempt was made to identify the upstream regulator of AtHKT1 , a close homolog of AoHKT1. Using chromatin immunoprecipitation, luciferase assay and yeast one-hybrid assays, WRKY9 was identified as the main transcription factor in the process. Furthermore, this was corroborated by the observation that AtHKT1 levels were significantly reduced in the atwrky9 seedlings. These findings revealed a part of the molecular regulatory mechanism of HKT1 induction in response to salt treatment in Arabidopsis. Our study suggests that AoHKT1 is a potential candidate for generating crop plants with increased salt tolerance. • Salt-responsive AoHKT1 was characterized from the mangrove Avicennia officinalis. • AoHKT1 increases salt tolerance in Arabidopsis by maintaining high shoot K+/Na+. • AoHKT1 transports both K+ and Na+ when expressed in yeast. • In Arabidopsis, AtHKT1 expression is reduced when AtWRKY9 is mutated. • WRKY9 transcription factor regulates HKT1 expression in plants. [ABSTRACT FROM AUTHOR]

Avicennia officinalis L. is a typical mangrove species, inhabiting inhospitable environments in the interface between sea and land. In this study, we generated RNA-seq data to de novo assemble the A. officinalis transcriptome. Starting with 36.24 million 100 bp paired-end reads, 38,576 high-confidence transcripts with an average length of 834 bp were produced after filtration of weakly expressed and redundant transcripts. We found known protein homologs for 22,254 of these transcripts, and assigned them to at least one of 119 gene ontology (GO) terms. In addition, we identified different copies and isoforms of three candidate genes, AoPIP , AoTIP and AoDHN1 , which might be involved in salt excretion via salt glands. All these genes were highly expressed in leaf tissue of A. officinalis , suggestive of a complicated mechanism of response to salt stress. We further identified 613 microsatellite markers for the assessment of genetic diversity and population differentiation in A. officinalis . Genomic resources generated in this study would be an important foundation for future research into molecular mechanisms underlying salt and other stress tolerance, as well as the evolutionary history of this mangrove species and its relatives. [ABSTRACT FROM AUTHOR]

Mangroves support numerous ecosystem services and help in reducing coastal ecological risks, yet they are declining rapidly due to climate change, sea level fluctuations and human activities. It is important to understand their responses to climate and sea level changes and identify conservation target areas at spatio-temporal scales, specifically in regions of rich mangrove biodiversity. In this study, we predicted the potential impact of past (Middle Holocene, ∼6000 years), current and future (2050s, 2070s; RCP 2.6 and RCP 8.5) climate change scenarios on the two dominant species in the coastal mangrove forest wetlands of India, i.e., Rhizophora mucronata and Avicennia officinalis through an ensemble species distribution modeling approach. The ensemble modeling has been carried out by integrating eight single algorithm methods. Based on the receiver operating characteristics of area under the curve (AUC) and true skill statistics (TSS) values the ensemble modeling has yielded the highest predictive performance for SVM for both the species and lowest by CART for R. mucronata and BIOCLIM for A. officinalis. The internal evaluation metrics of the resulting Species distribution models (SDMs) tested its robustness with AUC-0.97 and TSS-0.89 for A. officinalis and AUC-0.99 and TSS-0.90 for R. mucronata. Precipitation of Wettest Month (Bio 13) and Mean Temperature of Warmest Quarter (Bio 10) was the most important variable (54–67%) for the distribution of A. officinalis and Precipitation Seasonality (Bio 15) and Precipitation of Warmest Quarter (Bio 18) for R. mucronata. High precipitation and sea-level highstand during middle Holocene led to the maximum range expansion of suitable habitat for the mangrove species which is also validated in the present study by the fossil pollen datasets. Total mangrove habitat in current and future climatic scenarios decreased in 2.6 and 8.5 Representative Concentration Pathways (RCPs) for 2050 and 2070 which indicates the vulnerability of the species to climate change impacts. Mangrove species are projected to shift their ranges more towards land in future experiencing a decrease in the amount of suitable coastal area available to them throughout the Indian coastline. The plausible cause for this range shift may be due to higher precipitation that is usually associated with longer period of soil inundation and because of the rise in sea level. Our findings will assist in formulating species-specific restoration plans for these keystone species in context of climate change in the Indian Subcontinent. • Past, current and future prediction of two mangrove species in Indian coastline. • Ensemble of eight algorithms mapped the species distribution since Mid Holocene. • Landward range shift in future due to decline in suitable habitats along the coast. • Maximum range expansion mapped in mid Holocene validated by fossil pollen data. [ABSTRACT FROM AUTHOR]

Biota of coastal estuarine habitats of tropics and subtropics are extremely vulnerable. In the study, we have investigated the role of rhizosphere process in bio-accumulation of heavy metals in fine nutritive roots of riparian mangroves at eleven sampling locations of river Hooghly. The rhizospheric sediment of river Hooghly was accumulating HMs due to the presence of organic content and anthropogenic inputs. The mean EF (2.03–8.3), Igeo (−2.27–0.71), and CF (0.62–2.53) values signifies the enrichment of HMs in sediment fine fraction (<62.5 μm) whereas, the mean PLI (0.83 to 1.18) indicates gradual environmental degradation of river Hooghly. Low BCF observed in the river Hooghly might be due to barrier to hypodermal structures and/or any prevailing mechanism of saturation of HMs. However, BCF > 1 for Al, Cu, Cr, Mn, and Zn, signifies the phyto-remediation potential of riparian mangroves to mitigate amplified global anthropogenic environmental changes. • The organic content in rhizospheric sediment regulates heavy metal accumulation. • Sediment quality indices signify the enrichment of heavy metals in sediment fine fraction (<62.5 μm). • Fine nutritive root heavy metal concentration is directly proportional to the bio-availability of metal • BCF emphasizes the phyto-remediation potential of riparian mangroves. • The study highlights the significance of region specific integrated coastal management plan [ABSTRACT FROM AUTHOR]