Seasonal studies on the alginate and its biochemical composition I: Sargassum polycystum (Fucales), Phaeophyceae

Investigations were made on the brown seaweed Sargassum polycystum C. Agardh collected from Rameswaram Coast, Tamil Nadu. The alginates extracted from ‘leaf’, ‘stem’ and entire thallus of S. polycystum were investigated for their viscosity and chemical constituents, namely β‐D‐mannuronic acid (M‐block), α‐L‐guluronic acid (G‐block) and alternating sequences of β‐D‐mannuronic acid and α‐L‐guluronic acid (MG‐block) for six different seasons between August 1998 and November 1999. Significant seasonal variation (P< 0.05) was observed with high yield of alginate in February. The alginate extracted from the ‘leaf’ region showed a maximum yield whereas the ‘stem’ region exhibited maximum viscosity. The amount of G‐block was found to be more than M‐ and MG‐blocks in all the samples tested. The amount of G‐block was high in ‘stem’ followed by leaf and entire thallus. A positive correlation was recorded between viscosity and G‐block. Among the three alginates, the ratio of M/G was low in the ‘stem’ followed by ‘leaf’ and entire thallus.     

RDIS: The Rabies Disease Information System

Rabies is a deadly viral disease causing acute inflammation or encephalitis of the brain in human beings and other mammals. Therefore, it is of interest to collect information related to the disease from several sources including known literature databases for further analysis and interpretation. Hence, we describe the development of a database called the Rabies Disease Information System (RDIS) for this purpose. The online database describes the etiology, epidemiology, pathogenesis and pathology of the disease using diagrammatic representations. It provides information on several carriers of the rabies viruses like dog, bat, fox and civet, and their distributions around the world. Information related to the urban and sylvatic cycles of transmission of the virus is also made available. The database also contains information related to available diagnostic methods and vaccines for human and other animals. This information is of use to medical, veterinary and paramedical practitioners, students, researchers, pet owners, animal lovers, livestock handlers, travelers and many others.

Availability

The database is available for free http://rabies.mscwbif.org/home.html     

Co-evolutionary analysis of domains in interacting proteins reveals insights into domain-domain interactions mediating protein-protein interactions

Recent advances in functional genomics have helped generate large-scale high-throughput protein interaction data. Such networks, though extremely valuable towards molecular level understanding of cells, do not provide any direct information about the regions (domains) in the proteins that mediate the interaction. Here, we performed co-evolutionary analysis of domains in interacting proteins in order to understand the degree of co-evolution of interacting and non-interacting domains. Using a combination of sequence and structural analysis, we analyzed protein-protein interactions in F1-ATPase, Sec23p/Sec24p, DNA-directed RNA polymerase and nuclear pore complexes, and found that interacting domain pair(s) for a given interaction exhibits higher level of co-evolution than the non-interacting domain pairs. Motivated by this finding, we developed a computational method to test the generality of the observed trend, and to predict large-scale domain-domain interactions. Given a protein-protein interaction, the proposed method predicts the domain pair(s) that is most likely to mediate the protein interaction. We applied this method on the yeast interactome to predict domain-domain interactions, and used known domain-domain interactions found in PDB crystal structures to validate our predictions. Our results show that the prediction accuracy of the proposed method is statistically significant. Comparison of our prediction results with those from two other methods reveals that only a fraction of predictions are shared by all the three methods, indicating that the proposed method can detect known interactions missed by other methods. We believe that the proposed method can be used with other methods to help identify previously unrecognized domain-domain interactions on a genome scale, and could potentially help reduce the search space for identifying interaction sites.     

Morphological variation, histology, histochemistry and nutrient contents of Frankia root nodules in Casuarina equisetifolia

Root nodules were collected from the existing plantation of Casuarina equisetifolia from three different agroclimatic zones of Tamil Nadu, India. Morphological variation, histology, histochemistry and nutrient contents of the nodules were studied. The nodules were found to be simple, dichotomously branched and coralloid. The stele in simple and branched nodules reached up to the tip of the nodules. Structure of Frankia nodules was described using histochemical methods to elucidate the nature of micro-symbiont within the nodules. The nodule consisted of a distinct periderm enclosing the cortex. The cortex showed patches of infected cells interspersed among the uninfected ones. Inside the cortex was a stele bound by an endodermis, which contained high amount of tannin. The micro-symbiont was observed in the nodule tisues in hyphal form and spore packed sporocorp was also seen in the cortex. The histochemical tests revealed the presence of proteins, insoluble polysaccharides and polyphenols.     

Evidence for a higher number of species of Odontotermes (Isoptera) than currently known from Peninsular Malaysia from mitochondrial DNA phylogenies

Termites of the genus Odontotermes are important decomposers in the Old World tropics and are sometimes important pests of crops, timber and trees. The species within the genus often have overlapping size ranges and are difficult to differentiate based on morphology. As a result, the taxonomy of Odontotermes in Peninsular Malaysia has not been adequately worked out. In this study, we examined the phylogeny of 40 samples of Odontotermes from Peninsular Malaysia using two mitochondrial DNA regions, that is, the 16S ribosomal RNA and cytochrome oxidase subunit I genes, to aid in elucidating the number of species in the peninsula. Phylogenies were reconstructed from the individual gene and combined gene data sets using parsimony and likelihood criteria. The phylogenies supported the presence of up to eleven species in Peninsular Malaysia, which were identified as O. escherichi, O. hainanensis, O. javanicus, O. longignathus, O. malaccensis, O. oblongatus, O. paraoblongatus, O. sarawakensis, and three possibly new species. Additionally, some of our taxa are thought to comprise a complex of two or more species. The number of species found in this study using DNA methods was more than the initial nine species thought to occur in Peninsular Malaysia. The support values for the clades and morphology of the soldiers provided further evidence for the existence of eleven or more species. Higher resolution genetic markers such as microsatellites would be required to confirm the presence of cryptic species in some taxa.     

Functional Evolution of a Bark Beetle Odorant Receptor Clade Detecting Monoterpenoids of Different Ecological Origins

Insects detect odors using an array of odorant receptors (ORs), which may expand through gene duplication. How and which new functions may evolve among related ORs within a species remain poorly investigated. We addressed this question by functionally characterizing ORs from the Eurasian spruce bark beetle Ips typographus, in which physiological and behavioral responses to pheromones, volatiles from host and nonhost trees, and fungal symbionts are well described. In contrast, knowledge of OR function is restricted to two receptors detecting the pheromone compounds (S)-(–)-ipsenol (ItypOR46) and (R)-(–)-ipsdienol (ItypOR49). These receptors belong to an Ips-specific OR-lineage comprising seven ItypORs. To gain insight into the functional evolution of related ORs, we characterized the five remaining ORs in this clade using Xenopus oocytes. Two receptors responded primarily to the host tree monoterpenes (+)-3-carene (ItypOR25) and p-cymene (ItypOR27). Two receptors responded to oxygenated monoterpenoids produced in larger relative amounts by the beetle-associated fungi, with ItypOR23 specific for (+)-trans-(1R, 4S)-4-thujanol, and ItypOR29 responding to (+)-isopinocamphone and similar ketones. ItypOR28 responded to the pheromone E-myrcenol from the competitor Ips duplicatus. Overall, the OR responses match well with those of previously characterized olfactory sensory neuron classes except that neurons detecting E-myrcenol have not been identified. The characterized ORs are under strong purifying selection and demonstrate a shared functional property in that they all primarily respond to monoterpenoids. The variation in functional groups among OR ligands and their diverse ecological origins suggest that neofunctionalization has occurred early in the evolution of this OR-lineage following gene duplication.