DNA Barcoding of Invasive Terrestrial Plant Species in India.

Invasive plants are known to cause biodiversity loss and pose a major risk to human health and environment. Identification of invasive plants and distinguishing them from native species has been relied on morphological examination. Stringent requirement of floral characters and decreasing number of expert taxonomists are making conventional morphology-based identification system tedious and resource-intensive. DNA barcoding may help in quick identification of invasive species if distinct sequence divergence pattern at various taxonomic levels is observed. The present work evaluates the utility of four molecular markers; rbcL, matK, their combination (rbcL + matK), and psbA-trnH for identification of 37 invasive plant species from India and also in distinguishing them from 97 native species. A psbA-trnH locus was found to be of restricted utility in this work as it was represented by the members of a single family. A hierarchical increase in K2P mean divergence across different taxonomic levels was found to be the maximum for matK alone followed by rbcL + matK and rbcL alone, respectively. NJ clustering analysis, however, confirmed the suitability of combined locus (rbcL + matK) over individual rbcL and matK as the DNA barcode. RbcL showed the lowest resolution power among the three markers studied. MatK exhibited much better performance compared to rbcL alone in identifying most of the species accurately although it failed to show monophyly of genus Dinebra. Two families; Asteraceae and Poaceae, remained polyphyletic in the trees constructed by all three markers. Combined locus (rbcL + matK) was found to be the most suitable marker as it raised the resolution power of both the markers and could identify more than 90% of genera correctly. Phylogenetic tree constructed by Maximum-Parsimony method using combined locus as a molecular marker exhibited the best resolution, thus, supporting the significance of two-locus combination of rbcL + matK for barcoding invasive plant species from India. Present study contributes to the global barcode data of invasive plant species by adding fifty-one new sequences to it. Effective barcoding of additional number of native as well as invasive plant species from India is possible using this dual locus if it is combined with one or more new molecular plastid markers. Expansion of barcode database with a focus on barcode performance optimisation to improve discrimination ability at species level can be undertaken in future.

Optical detection of total cholesterol based on a dye-displacement method.

In the present study, the dye methylene blue (MB) was entrapped in an agarose gel and used as a sensing probe for the detection of total cholesterol. When methylene blue-entrapped agarose cubes were added to the cholesterol solution, methylene blue was displaced by cholesterol and released into the solution. A calibration curve was prepared by plotting the rate of release of methylene blue at 664 nm against varying cholesterol concentrations. A linear response was observed in the concentration range of 1 to 5 mM (40 mg/dL to 200 mg/dL) which covers normal and elevated cholesterol levels in humans. Optical detection of cholesterol using this dye-replacement method is simple, economical, and non-toxic. Characterisation of the system was carried out by FT-IR spectroscopy and cyclic voltammetry. The optical method was validated to determine total cholesterol in serum samples with reasonable accuracy.

Revisiting DNA barcoding of true bugs of the infraorder Pentatomomorpha (Hemiptera: Heteroptera) from India.

Cytochrome c oxidase subunit I gene (COI) sequences of roughly 509 bp length for various species of the Infraorder Pentatomomorpha were generated. K2P divergences within and between species and genera were calculated and compared using newly generated sequences and the ones available on online portals. Mean interspecific (within-genus) genetic divergence (14.23%) was ∼ eight times greater than mean intraspecific (within-species) divergence (1.79%). Distance-based as well as character-based approaches were used towards constructing (COI) trees. In total, 20 sequences were of the species that were previously not part of the Barcode Of Life Database (BOLD), hence representing additions to the barcode library of Indian Heteroptera. Some of the analyzed species are well-known agricultural pests. All the COI sequences and the associated specimen data have been deposited on BOLD.

DNA barcoding of Pentatomomorpha bugs (Hemiptera: Heteroptera) from Western Ghats of India.

Recent studies from East Asia and Canadian National Collection of Insects have established the utility of DNA barcoding technique in identification of true bugs. The present study is an expansion of the database by adding mitochondrial cytochrome c oxidase I (mtCOI) sequences from forty three species of indigenous true bugs of India. mtCOI gene analysis of infraorder Pentatomomorpha covering a total of seventy three species that belong to five superfamilies; Pentatomoidea, Coreoidea, Pyrrhocoroidea, Lygaeoidea and Aradoidea revealed more than 3% interspecific distances in all the taxa studied except for two cases which showed barcode sharing. Less than 2% intra-specific divergence was observed in 97% of the taxa analysed and the average interspecies genetic distance was about 29 times higher than the average intraspecies genetic divergence. Distinct sequence divergence pattern at generic level and NJ clustering analysis suggests that COI barcode is an excellent molecular marker for species level identification of unknown taxa; however it may not be useful for resolving deep levels of divergence. Species identification even at nymphal stage could be achieved confirming the efficacy of this technique.

Glutaraldehyde activated eggshell membrane for immobilization of tyrosinase from Amorphophallus companulatus: application in construction of electrochemical biosensor for dopamine.

Tyrosinase from a plant source Amorphophallus companulatus was immobilized on eggshell membrane using glutaraldehyde. Among the three different approaches used for immobilization, activation of eggshell membrane by glutaraldehyde followed by enzyme adsorption on activated support could stabilize the enzyme tyrosinase and was found to be effective. K(m) and V(max) values for dopamine hydrochloride calculated from Lineweaver-Burk plot were 0.67 mM and 0.08 mM min(-1), respectively. Studies on effect of pH showed retention of more than 90% activity over a pH range 5.0-6.5. Membrane bound enzyme exhibited consistent activity in the temperature range 20-45 degrees C. Shelf life of immobilized tyrosinase system was found to be more than 6 months when stored in phosphate buffer at 4 degrees C. An electrochemical biosensor for dopamine was developed by mounting the tyrosinase immobilized eggshell membrane on the surface of glassy carbon electrode. Dopamine concentrations were determined by the direct reduction of biocatalytically liberated quinone species at -0.19 V versus Ag/AgCl (3M KCl). Linearity was observed within the range of 50-250 microM with a detection limit of 25 microM.

Electrochemical biosensor for catechol using agarose-guar gum entrapped tyrosinase.

An electrochemical biosensor using tyrosinase was constructed for the determination of catechol. The enzyme was extracted from a plant source Amorphophallus companulatus and entrapped in agarose-guar gum composite biopolymer matrix. Catechol was determined by direct reduction of biocatalytically liberated quinone species at -0.1 V versus Ag/AgCl (3M KCl). The response was found to be linear and concentration dependent in the range of 6 x 10(-5) to 8 x 10(-4)M with a lower detection limit of 6 microM. It has reusability up to 20 cycles and a shelf life of more than 2 months when stored at 4 degrees C.

Development of electrochemical biosensor based on tyrosinase immobilized in composite biopolymeric film.

An electrochemical enzyme electrode for dopa and dopamine was developed via an easy and effective immobilization method. The enzyme tyrosinase was extracted from a plant source Amorphophallus companulatus and immobilized in a novel composite of two biopolymers: agarose and guar gum. This composite matrix-containing enzyme forms a self-adhering layer on the active surface of glassy carbon electrode, making it a selective and sensitive phenol sensor. Dopa and dopamine were determined by the direct reduction of biocatalytically liberated quinone species at -0.18V versus Ag/AgCl (3M KCl). The analytical characteristics of this sensor, including linear range, lower detection limit, pH, and storage stability, are described. It has reusability up to 15 cycles and a shelf life of more than 2 months.