Porteresia Research Articles

MORPHOMETRY, HABITAT AND STANDING CROP OF Porteresia coarctata AT BAKKHALI ESTUARY, COX’S BAZAR, BANGLADESH

Morphology, habitat, shoot density and standing crop (above and below ground biomass) of salt marsh Porteresia coarctata at Bakkhali estuary, Cox’s Bazar were investigated from January 2006 to June 2006. Permanent plots of 50 m x 50 m from exposed (station I) and protected (station II) areas were selected. P. coarctata was found growing as monospecific stand and four-species association with seagrass Halophila beccarii, patches of mangroves (Avicennia alba, A. marina and Acanthus ilicifolius) and the seaweed Ulva intestinalis in the intertidal sandy clay substrate. P. coarctata also grew in three-species association with mangrove and seaweed, or with seagrass and seaweed as well as in two-species association with seagrass and Imperata cylindrica. The range of mean leaf length, internodes length of rhizome and individual shoot height were found 8.10-14.49 cm, 0.91-1.41 cm and 12.90-20.94 cm, respectively. The mean shoot density varied from 925.0 to 1545.0 shoots m-2. The mean above and below ground biomass were 23.28-38.02 g DW (Dry Weight) m-2 and 60.26-97.39 g DW m-2, respectively. The pore water salinity, pH and NH4-N were recorded 17.0-41.66‰, 6.0-6.47 and 1.80-3.70 µg l-1, respectively. The variation of morphological parameters, shoot density and standing crop of P. coarctata between the two sampling stations attributed to the differences in habitat, soil organic matter and tidal action i.e., wave and current between the stations.

Expressing OsiSAP8, a Zinc-Finger Associated Protein Gene, Mitigates Stress Dynamics in Existing Elite Rice Varieties of the ‘Green Revolution’

Key message: Overexpression of OsiSAP8 driven by Port Ubi2.3 from Porteresia coarctata imparts drought and salinity stress tolerance in transgenic rice. Stress associated proteins (SAPs) possess the zinc-finger domains that are wildly evolving functional and conserved regions/factors in plants to combat abiotic stresses. In this study, the promoter region of OsiSAP8, an intron-less, multiple stress inducible gene, was compared in silico with a strong constitutive promoter, Port Ubi2.3. This resulted in developing rice, resistant to drought and salinity expressing OsiSAP8 promoted by Port Ubi2.3. (Porteresia coarctata), through Agrobacterium-mediated transformation in the popular rice varieties, IR36 and IR64. Southern blot hybridization confirmed the integration of OsiSAP8, and the T0 transgenic lines of IR36 and IR64 were evaluated for their drought and salinity tolerance. The IR36-T1 progenies showed an enhanced tolerance to water withhold stress compared to wild type and IR64-T1 progenies. Physiological parameters, such as the panicle weight, number of panicles, leaf wilting, and TBARS assay, showed the transgenic IR36 to be superior. The transgenic lines performed better with higher 80–95% relative leaf water content when subjected to drought for 14 days. Gene expression analysis of OsiSAP8 in IR36 T1 showed a 1.5-fold upregulation under mannitol stress. However, IR64 T1 showed a two-fold upregulation in NaCl stress. An enhanced drought and salinity stress tolerance in the transgenic IR36 cultivar through overexpression of OsiSAP8 was observed as it had a native copy of OsiSAP8. This is perhaps the first study using a novel ubiquitin promoter (Port Ubi2.3) to generate drought and salinity stress-tolerant transgenic rice. Thus, we report the overexpression of a rice gene (OsiSAP8) by a rice promoter (Port Ubi2.3) in rice (IR36) to resist drought and salinity.

A diagnostic phytolith morphotype found in Porteresia coarctata (Roxb.) Tateoka indicates coastal swampy mangrove environments: A case study from the Indian east coast

Porteresia coarctata (Roxb.) Tateoka is a true halophytic perennial wild grass that grows profusely along newly formed, highly saline landmasses and mudflats in the coastal mangroves of the Indian subcontinent and acts as a pioneer species in mangrove succession. Comprehensive phytolith analyses on sixteen P. coarctata samples collected from different swampy mangrove locations of four mangrove forests (Sundarbans, Bhitarkanika, Godavari and Krishna) along the Indian east coast show the significant and exclusive presence of a new specialized RONDEL having four distinct horns with flat base (named henceforth as RONDEL FOUR HORNED). Significant numbers of this morphotype have also been recorded in the surface sediment samples collected from these swampy mangrove sites. The RONDEL FOUR HORNED is a diagnostic phytolith morphotype of P. coarctata and a useful indicator of coastal swampy or intertidal mangroves of the Indian east coast. This morphotype was then used to identify past coastal intertidal mangrove environments in a late Quaternary sedimentary profile.

Eco-engineering of coastal environment through saltmarsh restoration towards climate change impact mitigation and community adaptation in Bangladesh

A field research was undertaken to investigate the effects of saltmarsh restoration and some eco-engineering activities on the climate change impact mitigation and community adaptation in the coastal environment of Sonadia Island, Cox’s Bazar, Bangladesh. Two research sites viz., saltmarsh restoration site (SMRS) and impacted site (IP) were selected for this study. Amount of carbon assimilation by saltmarsh plant Porteresia coarctata at SMRS was increased from 165.17 ± 68.35 to 198.18 ± 41.32 g/m2 during the study. The highest carbon assimilation (198.18 ± 41.32 g/m2) was noticed during winter, while the highest biomass (10.47 ± 0.25 kg/m2) was measured from SMRS. Soil compactness, organic matter, organic carbon, field water capacity, plant height, plant biomass and shoot density were found to be significantly (p < 0.05 to 0.01) higher in the SMRS than that of the IS. Seasonal variations of air temperature, water temperature, water pH, water salinity, water transparency, tidal height, inundation period, wave velocity, soil temperature, soil pH, pore water salinity, sedimentation, soil texture particle density, plant height, biomass and shoot density at different significance levels (p < 0.05 to p < 0.01) were noticed throughout the study. Correlation matrix showed that the plant height, biomass and shoot density were positively correlated with sedimentation, and negatively correlated with wave velocity at different significant levels (p < 0.05 to p < 0.01). From the present study, it is evident that SMRS, which was controlled and managed with some artificial inputs not only showed the elevated levels of plant height, biomass, shoot density, sedimentation and carbon assimilation but also exhibited remarkable changes in some of the factors studied rather than impacted site (IS), the findings of which could be helpful for the protection of coastal environment as well as mitigation of climate change impact that will ultimately save the local community from natural calamities in the long run.

Aquatic and edaphic determinants influencing carbon storage in a salt marsh grass, Porteresia coarctata, of the Bhitarkanika wildlife sanctuary and the Mahanadi estuary

In the present study, investigation was carried out in the Bhitarkanika and Mahanadi mangrove ecosystems during 2017–18 and 2018–19 on biomass and carbon of Porteresia coarctata, a salt marsh grass species of the Poaceae family. Water parameters such as temperature, pH, and salinity were measured along with soil parameters such as pH, electrical conductivity, bulk density, organic carbon, and soil texture, which were measured simultaneously. Growth pattern in terms of increase in biomass and carbon (in Mg ha−1) over the study period in Bhitarkanika was 1.03 ± 0.49 and 0.48 ± 0.22 and that of Mahanadi was 0.62 ± 0.17 and 0.29 ± 0.09, respectively. The correlation coefficient was computed for biomass and carbon of P. coarctata where salinity, soil bulk density, and soil organic carbon played a major role in governing the distribution of species. MANOVA results computed for both Bhitarkanika and Mahanadi showed significant difference between stations for both biomass and carbon of P. coarctata. However, other parameters of water and soil exhibited very weak relationship. Allometric models computed with AGB and AGC as dependent variables and physico-chemical variables as independent variables have revealed that salinity and OC are the major driving factors for growth and development as well as carbon storage potential of the species.

Bioaccumulation of potentially toxic elements in three mangrove species and human health risk due to their ethnobotanical uses.

The aim of thisstudy was to assess probabilistic human health risk due to ethnobotanical usage of Avicennia officinalis, Porteresia coarctata and Acanthus ilicifolius. The study was conductedat thetannery outfall near Sundarban (Ramsar wetland, India)mangrove ecosystem affected by potentially toxic elements (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn). Totalmetal concentrations (mg kg-1) were considerably higher in the pollutedrhizosphere namely, Cd (1.05-1.97), Cu (36.3-38.6), Cr (144-184), Hg (0.04-0.19), Mn (163-184), Ni (37.7-46.4), Pb (20-36.6), and Zn (97-104). Ecological risk index indicated low to moderate ecological risk in this site, whereas the ecological risk factor showed high potential ecological risk due to Cd pollution. BCRSequential extraction of metals showed more exchangeable fraction of Cd (47-55%), Cr (9-13%), Hg (11-13%), and Pb (11-15%), at the polluted site. Mercury, though present in trace amount in sediment, showed the highest bioaccumulation in all the three plants. Among the toxic trio, Hg showed the highest bioaccumulation in A. officinalis, Cd in P. coarctata but Pb has the lowest bioaccumulation potential in all the three species. Occasional fruit consumption of A. officinalis and dermal application of leaf, bark of A. officinalis (antimicrobial), A. ilicifolius (anti-inflammatory, pain reliever when applied on wounds) indicated negligible human health risk. However, long-term consumption of P. coarctata (wild rice variety) seeds posed health risk (THQ>1) both in adults and children age groups. This study concludes that nature of ethnobotanical use and metal contamination levels of the mangroverhizosphere can impact human health. The transfer process of potentially toxic elements from rhizosphere to plants to human body should be considered while planing pollution mitigation measures. Graphical Abstract.

HKT1;5 Transporter Gene Expression and Association of Amino Acid Substitutions With Salt Tolerance Across Rice Genotypes.

Plants need to maintain a low Na+/K+ ratio for their survival and growth when there is high sodium concentration in soil. Under these circumstances, the high affinity K+ transporter (HKT) and its homologs are known to perform a critical role with HKT1;5 as a major player in maintaining Na+ concentration. Preferential expression of HKT1;5 in roots compared to shoots was observed in rice and rice-like genotypes from real time PCR, microarray, and RNAseq experiments and data. Its expression trend was generally higher under increasing salt stress in sensitive IR29, tolerant Pokkali, both glycophytes; as well as the distant wild rice halophyte, Porteresia coarctata, indicative of its importance during salt stress. These results were supported by a low Na+/K+ ratio in Pokkali, but a much lower one in P. coarctata. HKT1;5 has functional variability among salt sensitive and tolerant varieties and multiple sequence alignment of sequences of HKT1;5 from Oryza species and P. coarctata showed 4 major amino acid substitutions (140 P/A/T/I, 184 H/R, D332H, V395L), with similarity amongst the tolerant genotypes and the halophyte but in variance with sensitive ones. The best predicted 3D structure of HKT1;5 was generated using Ktrab potassium transporter as template. Among the four substitutions, conserved presence of aspartate (332) and valine (395) in opposite faces of the membrane along the Na+/K+ channel was observed only for the tolerant and halophytic genotypes. A model based on above, as well as molecular dynamics simulation study showed that valine is unable to generate strong hydrophobic network with its surroundings in comparison to leucine due to reduced side chain length. The resultant alteration in pore rigidity increases the likelihood of Na+ transport from xylem sap to parenchyma and further to soil. The model also proposes that the presence of aspartate at the 332 position possibly leads to frequent polar interactions with the extracellular loop polar residues which may shift the loop away from the opening of the constriction at the pore and therefore permit easy efflux of the Na+. These two substitutions of the HKT1;5 transporter probably help tolerant varieties maintain better Na+/K+ ratio for survival under salt stress.

Functional screening of genes from a halophyte wild rice relative Porteresia coarctata in Arabidopsis model identifies candidate genes involved in salt tolerance

High soil salinity is one of the most important environmental stressors, and is an increasing concern under the alarmingly global climate uncertainties. Salinity affects the growth and productivity of food crops, including rice, and ultimately threatens global food security and sustainability. Conventional breeding efforts to develop salt tolerant rice varieties utilizing its primary gene pool have resulted in limited success due to the mutligenic inheritance of salt tolerance traits. On the other hand, Porteresia coarctata, the only halophyte wild rice, offers tremendous opportunities to improve salt tolerance in rice. However, reports on the characterization of its rich genetic resources are scanty. The present study was undertaken to functionally identify salt responsive genes of P. coarctata in Arabidopsis model using a cDNA overexpression (COX) strategy. COX-mediated hunting of transgenic Arabidopsis expressing a cDNA library of P. coarctata under control of a maize ubiquitin promoter identified 12 candidates that were involved in salt tolerance for seed germination, and seedling and reproductive growth. Of these, four genes coding for a metallothionein, a ribosomal protein, a photosystem II 10 kDa protein, and a ferredoxin:thioredoxin reductase conferred enhanced salt tolerance phenotypes, such as better root and shoot growth, and tissue tolerance by maintaining higher relative water content, membrane stability and protecting cells from reactive oxygen species. These genes could be ideal candidates for improving salt tolerance in rice; however, further studies are needed to ascertain their direct functional relevance in salt tolerance mechanisms.

Selective manipulation of the inositol metabolic pathway for induction of salt-tolerance in indica rice variety

Halophytes are rich sources of salt stress tolerance genes which have often been utilized for introduction of salt-tolerance character in salt-sensitive plants. In the present study, we overexpressed PcINO1 and PcIMT1 gene(s), earlier characterized in this laboratory from wild halophytic rice Porteresia coarctata, into IR64 indica rice either singly or in combination and assessed their role in conferring salt-tolerance. Homozygous T3/T4 transgenic plants revealed that PcINO1 transformed transgenic rice lines exhibit significantly higher tolerance upto 200 mM or higher salt concentration with negligible compromise in their growth or other physiological parameters compared to the untransformed system grown without stress. The PcIMT1-lines or the double transgenic lines (DC1) having PcINO1 and PcIMT1 introgressed together, were less efficient in such respect. Comparison of inositol and/or pinitol pool in three types of transgenic plants suggests that plants whose inositol production remains uninterrupted under stress by the functional PcINO1 protein, showed normal growth as in the wild-type plants without stress. It is conceivable that inositol itself acts as a stress-ameliorator and/or as a switch for a number of other pathways important for imparting salt-tolerance. Such selective manipulation of the inositol metabolic pathway may be one of the ways to combat salt stress in plants.

Lipid content and fatty acid profile of selected halophytic plants reveal a promising source of renewable energy

Recent research has focused on the production of biofuel from different bio-resources, especially non-edible and underutilized plants. In this study, total lipid contents and fatty acids composition were evaluated both qualitatively and quantitatively for twelve abundant halophytes to ascertain their potential as feedstock for renewable energy. Non-succulent halophytes contained the highest total lipid content (about 5–7%, except Porteresia coarctata), followed by shrubby (about 2.6%) and succulent halophytes (1–1.8%). The FA profile shows that halophytes are a rich source of alpha-linolenic, linolenic and palmitic acids. Oleic and stearic acids were also detected in some halophytes. A low content of MUFA (except P. coarctata) was detected in all the halophytes, but the maximum content of SFA was estimated in Salicornia brachiata, Suaeda fruticosa, and P. coarctata. Halophyte Sporobolus virginicus contained more than 80% PUFA, followed by Heleochloa setulosa, Sesuvium portulacastrum, Atriplex griffithii and Salvadora persica. An important qualitative indicator density was found to be at par with recommended standards, but the cetane number of S. fruticosa and S. brachiata also matched the standards. The overall fatty acid profile of the selected halophytes makes them suitable for biofuel, and their potential could be enriched by improving agronomical practices and downstream processing.

Expression of wild rice Porteresia coarctata PcNHX1 antiporter gene (PcNHX1) in tobacco controlled by PcNHX1 promoter (PcNHX1p) confers Na+-specific hypocotyl elongation and stem-specific Na+ accumulation in transgenic tobacco

Soil salinization is a major abiotic stress condition that affects about half of global agricultural lands. Salinity leads to osmotic shock, ionic imbalance and/or toxicity and build-up of reactive oxygen species. Na⁺/H⁺ antiporters (NHXs) are integral membrane transporters that catalyze the electro-neutral exchange of K⁺/Na⁺ for H⁺ and are implicated in cell expansion, development, pH/ion homeostasis and salt tolerance. Porteresia coarctata is a salt secreting halophytic wild rice that thrives in the coastal-riverine interface. P. coarctata NHX1 (PcNHXI) expression is induced by salinity in P. coarctata roots and shows high sequence identity to Oryza sativa NHX1. PcNHX1 confers hygromycin and Li+ sensitivity and Na+ tolerance transport in a yeast strain lacking sodium transport systems. Additionally, transgenic PcNHX1 expressing tobacco seedlings (PcNHX1 promoter) show significant growth advantage under increasing concentrations of NaCl and MS salts. Etiolated PcNHX1 seedlings also exhibit significantly elongated hypocotyl lengths in 100 mM NaCl. PcNHX1 expression in transgenic tobacco roots increases under salinity, similar to expression in P. coarctata roots. Under incremental salinity, transgenic lines show reduction in leaf Na+, stem specific accumulation of Na+ and K+ (unaltered Na+/K+ ratios). PcNHX1 transgenic plants also show enhanced chlorophyll content and reduced malondialdehyde (MDA) production in leaves under salinity. The above data suggests that PcNHX1 overexpression (controlled by PcNHX1p) enhances stem specific accumulation of Na+, thereby protecting leaf tissues from salt induced injury.

Draft genome sequence of first monocot-halophytic species Oryza coarctata reveals stress-specific genes

Oryza coarctata (KKLL; 2n = 4x = 48, 665 Mb) also known as Porteresia coarctata is an extreme halophyte species of genus Oryza. Using Illumina and Nanopore reads, we achieved the assembled genome size of 569.9 Mb, accounting 85.69% of the estimated genome size with N50 of 1.85 Mb and 19.89% repetitive region. We also found 230,968 simple sequence repeats (SSRs) and 5,512 non-coding RNAs (ncRNAs). The functional annotation of predicted 33,627 protein-coding genes and 4,916 transcription factors revealed that high salinity adaptation of this species is due to the exclusive or excessive presence of stress-specific genes as compared to rice. We have identified 8 homologs to salt-tolerant SOS1 genes, one of the three main components of salt overly sensitive (SOS) signal pathway. On the other hand, the phylogenetic analysis of the assembled chloroplast (134.75 kb) and mitochondrial genome (491.06 kb) favours the conservative nature of these organelle genomes within Oryza taxon.

Functional characterization of two myo-inositol-1-phosphate synthase (MIPS) gene promoters from the halophytic wild rice (Porteresia coarctata).

The promoter deletion mutants from second isoform of INO1 (gene-encoding MIPS) from Porteresia coarctata of 932bp (pPcINO1.2.932) and 793bp (pPcINO1.2.793) prove to be very efficient as salt/drought stress-inducible promoters, while pPcINO1.2.932 is found to be responsive to cold stress as well. The promoters of the two identified myo-inositol-1-phosphate synthase (INO1) isoforms from salt-tolerant wild rice, Porteresia coarctata (PcINO1.1 and PcINO1.2) have been compared bioinformatically with their counterparts present in the salt-sensitive rice, Oryza sativa. PcINO1.2 promoter was found to be enriched with many abiotic stress-responsive elements, like abscisic acid-responsive elements, MYC-responsive elements, MYB-binding sites, low-temperature stress-responsive elements, and heat-shock elements similar to the ones found in the conserved motifs of the promoters of salt/drought stress-inducible INO1 promoters across Kingdom Planta. To have detailed analysis on the arrangement of cis-acting regulatory elements present in PcINO1 promoters, 5' deletion mutational studies were performed in dicot model plants. Both transient as well as stable transformation methods were used to check the influence of PcINO1 promoter deletion mutants under salt and physiologically drought conditions using β-glucuronidase as the reporter gene. The deletion mutant from the promoter of PcINO1.2 of length 932bp (pPcINO1.2.932) was found to be significantly upregulated under drought stress and also in cold stress, while another deletion mutant, pPcINO1.2.793 (of 793bp), was significantly upregulated under salt stress. P. coarctata being a halophytic species, the high inducibility of pPcINO1.2.932 upon exposure to low-temperature stress was an unexpected result.

Characterization of Progenies from Intergeneric Hybridization Between Oryza sativa L. and Porteresia coarctata (Roxb.) Tateoka

Porteresia coarctata (Roxb.) Tateoka is an endemic halophyte growing all over the coastal belt of Bangladesh, propagating through rhizomes and setting a few ricelike grains. So exploiting the genetic potential of this wild rice as salt tolerant donor in possible wide crosses with rice (2n = 24) could be useful. We attempted intergeneric hybridization between Oryza sativa L. and P. coarctata. The survival rate of hybrid progenies in embryo culture was low but among them 2 hybrid plants were successfully matured from the intergeneric cross between the cultivated induced tetraploid of rice, Latisail (2n = 4x = 48) and P. coarctata (2n = 48). The hybrid plants could be successfully established in soil and were not like either of the parents in morphology although some of their features were similar to their maternal parent, Latisail (4x). Both of the hybrids were investigated through physiological analysis under salinity stress and molecular analyses with rice specific SSR markers. Molecular analysis of the F1 DNA with only 3 SSR markers, RM581, RM20224 and RM25271, out of 36 others tested, showed bands specific to both of the parents, while all had common bands with the maternal parent. Dendrogram analysis of the hybrids with the 36 SSR markers, show that P. coarctata forms a different clade and is clearly separated from Latisail and the hybrids. The putative hybrids however made a subgroup with Latisail. These observations could be possibly explained if chromosome loss of the paternal parent had occurred or may be it was a pleotropic effect of intergeneric hybridization. Physiological screening of the hybrid progenies at the F2 generation in seedling stage showed better result in leaf damage score (LDS) and salinity tolerance than their maternal parent Latisail (4x) at 150 mM salt stress for 10 days. F2 plants from one of the hybrid plants (H‐2) showed better performance but there was a large variation in response from each of the individual progenies. So, it is likely that some of the salt tolerant characteristics of the pollen parent might have been transferred to the recipient Latisail (4x). For introgression of better salt tolerant loci from P. coarctata, more wide hybrids will need to be produced and repeatedly crossed with P. coarctata.Plant Tissue Cult. &amp; Biotech. 27(1): 63-76, 2017 (June)

Native salt-tolerant grass species for habitat restoration, their acclimation and contribution to improving edaphic conditions: a study from a degraded mangrove in the Indian Sundarbans

The Sundarbans is the largest continuous block of mangrove distributed over both India and Bangladesh and is threatened with pronounced erosion and mudflat degradation in its western reaches. Since 2013, considerable progress has been achieved through the restoration of highly degraded mudflats by the extensive utilization of four native grass species plantings, Porteresia coarctata, Myriostachya wightiana, Paspalum vaginatum, and Sporobolus virginicus. These grasses proved to exhibit the highest survival (80–90%) in the lower and middle intertidal zone and during the last three years (2013–2016) almost 6000 m2 area have been restored by the growth of these grasses. Increased osmolyte synthesis under degraded conditions in these native grasses offered osmotic protection and helped to expand and restore the mudflat to an elevation suitable for mangrove establishment. The rhizosphere of the four grasses was engaged in the decomposition cycle, releasing more nutrients, more nutrient cycling soil microbial enzymes, and encouraged high densities of nutrient cycling bacteria. The study demonstrates that stabilization and reclamation of the denuded mudflat by halotolerant grasses is an essential prerequisite for any successful mangrove restoration program. The facilitative role of the salt marsh is crucial to aid colonization by mangrove propagules.

Long-Term Exposure to Combined Treatment of Elevated CO&lt;sub&gt;2&lt;/sub&gt; and Salt Induces Iron Deficiency Responses in &lt;i&gt;Porteresia coarctata&lt;/i&gt;

Plants with rising atmospheric carbon dioxide (CO 2 ) level in the environment may change their nutrient demands to sustain growth. The mechanisms concerning iron dynamics in plants under the interactive effect of salinity and elevated CO 2 are poorly understood. This study examines the effects of long-term as well as short-term growth at elevated CO 2 and salt on iron deficiency-associated molecular responses of Porteresia coarctata through analysing the transcript expression of iron deficiency-responsive genes in the leaf tissue. Plants were grown in hydroponic media at ambient or elevated atmospheric CO 2 (500 μl l -1 ), with or without salt, and samples were analysed at three time points, on the 15th, 45th and 90th day. The semiquantitative RT-PCR analysis showed an induced expression of iron deficiency-responsive transcription factor PcIDEF1 and its putative targets OsIRO2-like gene, OsNAAT1-like gene, OsNAS1-like gene, OsYSL2- like gene and PcIRT1 at elevated CO 2 with NaCl. Furthermore, a positive correlation in gene expression was observed between PcIDEF1 and its putative targets in the 15th and 45th day samples. By contrast, in the 90th day sample, correlation in gene expression was less evident. Our findings suggest that the interactive effect of elevated CO 2 and NaCl can induce a set of molecular responses in P. coarctata for enhanced iron uptake and utilization, thereby reflecting an iron deficiency like stress under such conditions.

Saltmarsh and seagrass beds on the south-eastern coast of Bangladesh: vegetation characteristics and adjacent fisheries diversity

AbstractSaltmarsh and seagrass communities are coastal macrophytes. These communities perform a number of important ecological functions, one of which is to support substantial fishery resources either as a nursery ground or a refuge from predators. The Bangladesh coast houses saltmarsh and seagrass resources but there has been sparse information on the diversity of fisheries adjacent to these plant communities. Consequently, this study was carried out to obtain information on the shoot density and biomass of the dominant saltmarsh (Porteresia coarctata) and seagrass (Halophila beccarii) species together with the diversity of fisheries adjacent to saltmarsh and seagrass beds on the south eastern coast of Bangladesh. The below-ground biomass of P. coarctata was found to be significantly higher than the above-ground biomass, presumably so as to survive under harsh environmental conditions, for example strong wave exposure. The standing crops and shoot density of the seagrass H. beccarii showed a similar pat...

Identification and characterization of a novel iron deficiency and salt stress responsive transcription factor IDEF1 in Porteresia coarctata

Iron availability affects plant growth depending on soil type. Mangroves are characterized by alkaline soils in which the halophytic wild rice relative Porteresia coarctata thrives. Young plants of P. coarctata grew optimally in the presence of 150 mM NaCl in a hydroponic medium and tolerated iron deficiency and salt up to 21 d without showing any symptoms of stress. A homolog of the rice iron deficiency responsive cis-acting element binding factor (IDEF1) that functions at the base of an iron regulated network was isolated and characterized from P. coarctata. PcIDEF1 had a close paralog in P. coarctata genome and its transcript expression was upregulated by both iron deficient conditions and salt treated conditions for up to three weeks. Sub-cellular localization study suggests nuclear targeting PcIDEF1 protein in guard cells and root tissues of tobacco. In vitro assays for metal binding affinity and binding PcIDEF1 to iron deficiency responsive element 1 (IDE1)-like elements in the 5’ flanking region of an iron regulated transporter from P. coarctata suggest that PcIDEF1 could potentially sense iron content in a plant cell and regulate expression of iron responsive genes containing IDE1-like elements in their promoter region. This study provides evidence for a possible cross-talk between iron deficiency and salt responses.

Wild rice (Oryza spp.) germplasm collections from gangetic plains and eastern region of India: Diversity mapping and habitat prediction using ecocrop model

Wild Rice (Oryza Spp.) Germplasm Collections from Gangetic Plains and Eastern Region of India: Diversity Mapping and Habitat Prediction using Ecocrop Model Wild rice collections form the priority target group among rice germplasm for characterization, evaluation, conservation and utilization. So far 889 accessions of wild rice (Oryza spp.) germplasm were collected by ICAR-NBPGR from Gangetic Plains and eastern region of India in last four decades. Passport information on assembled germplasm was used to know habitat specificity and diversity pattern to predict their distribution; this will help execution of explorations. Germplasm accessions belonging to six different wild rice taxa–Oryza meyeriana var. granulata (4), O. nivara (484), O. officinalis (50), O. rufipogon (367), O. sativa var. spontanea (18) and Porteresia coarctata (10) were collected from Gangetic Plains and eastern region of India. GIS mapping had shown that maximum numbers of wild rice species were collected from north-western and north-eastern regions of Odisha. In this study, we used current (1950-2000) and projected climate data for 2050 through ‘EcoCrop’ model to predict habitat suitability areas for wild rice. Predicted habitat suitability map (1950-2000) had shown that at present >80% area of Gangetic Plains and eastern region of India are suitable for wild rice occurrence. Projection for 2050 indicated that nearly 47.7% areas becoming less suitable for wild rice distribution, indicating urgent need for exploration in prioritized areas for wild rice, particularly in these regions of India....

The Possible overlap between Salinity and Mechanical Challenges in &lt;I&gt;Porteresia Coarctata&lt;/I&gt;

In nature, certain abiotic stresses constitutively acting on plants often go unrecognized. Mechanical stress is one of such stresses, which is manifested on a plant as low-spectrum pressure on the cell membrane due to wind, soil hindrance, gravity or wave current. Although all plants face constant threats from mechanical stress, some ecosystems are more prone to receive such stress. Mangrove vegetation is daily inundated by saline tidal waves that pose a serious threat to the soil binding force of forest undergrowth. Porteresia coarctata is a mangrove rice, which being wild, is avaluable germplasm for bioprospecting of genes and proteins that may confer salt-tolerance to domestic rice. However, P. coarctata is important from ecological point of view as its salt and mechanical stress tolerance is an integral part of the mangrove ecosystem. It is not possible to understand the basic biology of P. coarctata without an ecological perspective. The subterranean part of Porteresia provides a high anchorage and binds soil, thus stabilizing the mangrove vegetation. The root system architecture of Porteresia is unique, with a rhizome and rhizoid-like rootlets. The root system interacts with both salinity and mechanical threat directly, and thus it is important to understand the molecular ecophysiology of Porteresia root and rhizomes to understand the nature of overlap between salinity and mechanical stress in a mangrove ecosystem, which is still elusive.