Browsing by Author "Siridewa, K."

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Cloning and characterization of a repetitive DNA sequence specific for Wuchereria bancrofti
(American Society of Tropical Medicine and Hygiene, 1994) Siridewa, K.; Karunanayake, E.H.; Chandrasekharan, N.V.; Abeyewickreme, W.; Franzen, L.; Aslund, L.; Pettersson, U.
A genomic library constructed in a bacteriophage lambda replacement vector (EMBL3) with Wuchereria bancrofti DNA partially digested with Sau 3A I was screened with 32P-labeled W. bancrofti total DNA, and a strongly reactive recombinant, EMBL3Wb34, was isolated. This clone contained an approximately 16-kb insert that showed some cross-hybridization with Brugia malayi and B. pahangi DNA. However, a 969-bp subclone from EMBL3Wb34, designated pWb12, hybridized only with W. bancrofti DNA and was able to detect as little as 300 pg. Furthermore, pWb12 could detect DNA from a single infective larva or one microfilaria. It has a moderate copy number (450-700) and appears to be interspersed within the parasite genome. The nucleotide sequence contains 66% A+T and 34% G+C and shows no notable internal repeats.
Morphological and molecular identification of different morphotypes of Suaeda maritima from Puttalam district in Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Jayasundara, R.; Siridewa, K.; Neththipola, T.; De Silva, W. L.; Perera, D.; Attanayake, R. N.
Suaeda is a genus belonging to the family Amaranthaceae (Chenopodiaceae) and comprises more than 100 species that are distributed all over the world. Members of the genus are mainly used for food, feed, and medicine. Three Suaeda species have been reported in Sri Lankan salt marshes among them, S. maritima is widely distributed. During a field survey in Seguwanthive in July 2022, two clearly distinct morphotypes of tentatively identified S. maritima were found. This tentative identification was done purely based on morphological characteristics. One morphotype had green stems and leaves while the other had reddish-green leaves and brightly red-colored stems. No reproductive parts were found at the time of the survey. Even though, previous reports indicated high phenotypic plasticity among the members of the genus, it was not clear whether both morphotypes belonged to the same species or not. Due to the lack of floral structures throughout the year, accurate species identification was a great challenge for a layperson and for a trained taxonomist. Therefore, the current study was conducted to obtain detailed morpho molecular identification of each morphotype of Suaeda maritima, and to confirm their species identity using molecular data as well. Plant samples were collected from Seguwanthive area mainly focusing on two morphotypes and documented. Leaves were succulent, linear in shape, flattened only on one side, and acute in the apex. Plants were 40-65 cm range in height in both morphotypes with a woody base. Flowers were observed only on green plants by the time of sampling, and they were bisexual and contained 5 stamens and 3 stigmas and located axillary in 2 mm diameter clusters and seeds were black, smooth and glossy, and suborbicular to ovoid in shape. Molecular identification was conducted using DNA barcoding approach. Genomic DNA extraction was optimized. The nuclear ribosomal ITS (Internal transcribed spacer) region was PCR (Polymerase chain reaction) amplified using universal primers BLASTn searchers of the sequences confirmed that both morphotypes were identical and 100% similar to previously published records of S. maritima (KF866384). This project findings give insights into the plant’s phenotypic plasticity under its natural environment and can be used as a future guide.
A Simple and rapid non-radioactive oligonucleotide based hybridization assay for the detection of Wuchereria bancrofti.
(SEAMEO Regional Tropical Medicine and Public Health Project, 1999) Gunawardene, Y.I.N.S.; Wijesundera, W.S.; Karunanayake, E.H.; Chandrasekharan, N.V.; Jayasekara, N.; Siridewa, K.
Five biotin labeled oligonucleotides was designed based on a previously cloned and characterized repetitive DNA sequence specific for Wuchereria bancrofti. The oligonucleotide mix (containing five probes) when used in a hybridization assay, detected as little as 100 pg of purified W. bancrofti, microfilarial DNA, a single infective stage larva and a single microfilaria in 50 microl blood sample. A simple protocol was followed for the hybridization assay. Blood samples lysed with sterile distilled water and digested with proteinase K in the presence of a detergent were directly applied on to nylon membranes for dot blot assays. The DNA extract of mosquitos carrying infective stage larvae was eluted through sephadex G-50 minicolumns prior to blotting. The assay was also able to detect DNA extracted from microfilariae infected samples stored over five days at room temperature (28 degrees C). This simple and rapid oligonucleotide hybridization protocol with the highly sensitive chemiluminescent-based detection has significant potential for the development of a field kit to detect W. bancrofti infection.
Species identification and pollination biology of an economically important true halophyte, Salicornia brachiata Roxb.
(Aquatic Botany, 2024) Siridewa, K.; De Silva, W.; Ratnayake, R.; Wijesundara, S.; Perera, D.; Attanayake, R. N.
Members of the genus Salicornia have gained a global attraction due to their ability to thrive under high saline conditions and as potential candidates in saline agriculture. However, it has been a taxonomically challenging genus for decades since the members show plastic responses to extreme environmental conditions and due to incongruences between morphological and molecular identification methods. While only a handful of commercially grown Salicornia species are fully described, most of the species including S. brachiata, a native species in the Indian sub-continent, Myanmar, and Sri Lanka are poorly described. With the potentials in adapting S. brachiata in saline agriculture, the aim of this study was to establish a morphology and DNA barcodebased species delineation system and to study pollination biology for future crop improvement projects. Tentatively identified S. brachiata plant samples were collected from two populations in Sri Lanka and completely described. GenBank lacked authenticated barcode data for S. brachiata except for one chloroplast genome to which the matK sequence obtained in the present study matched with 100 % identity. For the first time, well defined sequences of three barcode regions, ITS, ETS and matK, of S. brachiata were made available for accurate species identification. Reproductive dynamics in different parts of the inflorescence was studied. A facultative xenogamous mating system was recorded for the first time in the genus and while the lower florets in the cladode showed a preference towards outcrossing, the upper florets displayed adaptations for selfing. Data could be effectively utilized in future Salicornia breeding programs.