PCR-based molecular characterization, phylogenetic analysis and secondary structure of the 28S rDNA of Thaparocleidus wallagonius (Monogenea: Dactylogyridae) �C the most primitive species of this genus from India

Species of the monogenean genus Thaparocleidus are specific to freshwater siluriform fish. The infection caused by these gill parasites are a major health problem to fish. But, to focus the control strategies of these parasites, first it is important to establish an accurate discrimination by molecular methods. In the present study, phylogenetic and structural analysis of 28S region of ribosomal DNA of T. wallagonius species collected from fish Wallago attu from Meerut (U.P.), India, was carried out. In the first step, we amplified, sequenced 28S region of ribosomal DNA of T. wallagonius to establish the phylogenetic relationship with other species of this genus. T. wallagonius found on gill filaments of fish W. attu, is the most primitive parasite of this genus from India, was unequivocally discriminate from other species of the same genus in this study. A secondary-structure model of the large subunit rDNA was also predicted using a combined comparative and thermodynamic approach. Molecular morphometric and phylogenetic relationship of T. wallagonius are discussed in detailed that based on molecular analysis using bioinformatic tools.     

Prevalences of Shiga Toxin Subtypes and Selected Other Virulence Factors among Shiga-Toxigenic Escherichia coli Strains Isolated from Fresh Produce

Shiga-toxigenic Escherichia coli (STEC) strains were isolated from a variety of fresh produce, but mostly from spinach, with an estimated prevalence rate of 0.5%. A panel of 132 produce STEC strains were characterized for the presence of virulence and putative virulence factor genes and for Shiga toxin subtypes. About 9% of the isolates were found to have the eae gene, which encodes the intimin binding protein, and most of these belonged to known pathogenic STEC serotypes, such as O157:H7 and O26:H11, or to serotypes that reportedly have caused human illness. Among the eae-negative strains, there were three O113:H21 strains and one O91:H21 strain, which historically have been implicated in illness and therefore may be of concern as well. The ehxA gene, which encodes enterohemolysin, was found in ∼60% of the isolates, and the saa and subAB genes, which encode STEC agglutinating adhesin and subtilase cytotoxin, respectively, were found in ∼30% of the isolates. However, the precise roles of these three putative virulence factors in STEC pathogenesis have not yet been fully established. The stx_1a and stx_2a subtypes were present in 22% and 56%, respectively, of the strains overall and were the most common subtypes among produce STEC strains. The stx_2d subtype was the second most common subtype (28% overall), followed by stx_2c (7.5%), and only 2 to 3% of the produce STEC strains had the stx_2e and stx_2g subtypes. Almost half of the produce STEC strains had only partial serotypes or were untyped, and most of those that were identified belonged to unremarkable serotypes. Considering the uncertainties of some of these Stx subtypes and putative virulence factors in causing human illness, it is difficult to determine the health risk of many of these produce STEC strains.     

Kinetics of serotonin in platelets in essential hypertension.

In a study of the kinetics of 5-hydroxytryptamine (5-HT) in platelets in 26 hypertensive subjects with a mean systolic and diastolic blood pressure of 153.9 +/- 26.9 and 106.9 +/- 9.1 mm Hg respectively, it has been observed that in hypertensive platelets there was a marked decrease in 5-HT uptake and content, an increase in 5-HT efflux and an accompanying increase in Plasma 5-HT and 5-HIAA levels. Regression analysis of the data indicated a significant correlation between rise in diastolic blood pressure and these changes in 5-HT kinetics.     

Diversity and variability in seed characters and growth of Pongamia pinnata (L.) Pierre accessions

A thorough and extensive wild germplasm exploration survey was undertaken and 50 high yielding candidate plus trees (CPTs) of Pongamia pinnata (L.) Pierre from different locations from a latitudinal and longitudinal spread between 12°41′ and 22°E longitude and 77° and 84°40′N latitude covering 11 locations in an area spread of 150,000 km² were collected for evaluating genetic association and variability in seed and growth characters. There were significant differences observed in seed morphology and oil content as was in plant height, and number of branches in the progeny trial. Plant height and number of branches exhibited much higher values of both phenotypic and genotypic variance than observed in the seed characters. Among seed characters oil content exhibited highest broad sense heritability of more than 93% followed by seed length (90.0%). In contrast seed width showed the second highest genetic advance of 5.64% following the highest genetic advance of 10.15% exhibited by oil content. Hierarchical clustering by Ward’s Minimum Variance Cluster Analysis method showed phylogeographic patterns of genetic diversity. K means clustering revealed that trees from different geographic regions were grouped together in a cluster and as were trees from the same geographical area placed in different clusters suggesting that geographical diversity did not go hand in hand with genetic diversity. In addition clustering identified promising accessions with favourable traits for future establishment of orchards.     

Rice can acclimate to lethal level of salinity by pretreatment with sublethal level of salinity through osmotic adjustment

The physiological ability to adapt for various environmental changes is known as acclimation. When exposed to sublethal level of stress, plants develop the ability to withstand severe stress, as acquired tolerance. The present study was conducted to explicate the physiological basis of acquired tolerance in rice. Rice seedlings (variety IR 20) were grown in half strength Hoagland solution, and after 22nd day, they were kept in half strength Hoagland solution containing 50 mM NaCl (sublethal dose) for 7 days followed by half strength Hoagland solution containing 100 mM NaCl (lethal dose) for another 7 days. The non-pretreated 29 days old rice seedlings maintained in half strength Hoagland solution were directly transferred to half strength Hoagland solution containing 100 mM NaCl (lethal dose) solution for 7 days. The control plants were maintained in half strength Hoagland solution without NaCl. Various morphological and physiological parameters were recorded on 29th and 36th days old seedlings from control, pretreated and non-pretreated plants. The results revealed significant reduction in growth parameters (shoot length, root length, leaf area and total dry matter production) of non-pretreated plants below that of pretreated plants. The pretreated plants showed increased values to the extreme of 19.8 per cent in leaf water potential (ψ_w), 9 per cent in relative water content (RWC), 26 per cent in photosynthetic rate (P _N), 28 per cent in leaf stomatal conductance, and 47 per cent in chlorophyll a over non-pretreated plants. The same trend was also observed in chlorophyll a/b ratio (6.6%) and F _v/F _m ratio (19.3%). However, a reverse trend was seen in F _o value. The pretreated plants showed improved ionic regulation as evident from low Na⁺, Cl⁻ and high K⁺ contents, which is attributed to enhanced plant water status and photosynthesis. Both pretreated and non-pretreated plants had higher contents of osmolytes viz., sucrose, leaf soluble sugars and proline contents than control plants. However, starch content revealed an inverse trend. Therefore, the present study reveals that rice can acclimate to lethal dose of salinity stress by pretreatment with sublethal dose of NaCl. Section Editor: J. M. Cheeseman