The morpho-genetic and ecological niche analyses reveal the existence of climatically restricted Cycas zeylanica complex in Sri Lanka.

Taxonomy and phylogenesis of Sri Lankan cycad species of the subsection Rumphiae has not been fully resolved and therefore, we conducted an island-wide survey of cycads of the subsection to assess their morphological or genetic variations while exploring the phylogenetic relationship between Sri Lankan Rumphiae and other world cycad species. Further, we assessed the possible distribution of the species in the region through climatic profiling, using maximum entropy modeling approach. We analyzed 21 variable morphological features in collected specimens and used the polymorphism of trnH-psbA locus to understand the phylogeny. The distance tree drawn from the principal component analysis revealed a significant variation in female reproductive structures. The maximum likelihood tree separated Sri Lankan Cycas zeylanica to a well-supported unigeneric clade (bootstrap = 96, posterior probability = 100) with shallow divergence. Ecological niche modeling supported the existence of Cycas zeylanica in South East Asia and in southern Western Ghats in India in addition to the Wet Zone of Sri Lanka. We rename the taxa as Cycas zeylanica complex based on the observed high morphological diversity of female reproductive structures which might have ascended due to multiple introductions of South East Asian cycads by long distance dispersal of seeds through sea currents.

Genotypes of hepatitis C virus (HCV) in liver disease patients in Sri Lanka.

A total of 460 samples (serum or plasma) were obtained from clinically diagnosed liver disease patients from January 2006 to December 2007 and subjected to reverse transcription--polymerase chain reaction (RT-PCR) based detection of HCV. Of these, 32 samples (6.9%) were positive for HCV RNA. Samples that were positive for HCV were genotyped with type specific primers. The genotyping assay was validated by DNA sequencing and phylogenetic analysis. The Sri Lankan isolates were comprised predominantly of genotype 1b (46.9%) followed by genotype 2b (21.9%), 2a (15.6%) and mixed infection with genotypes 1b and 2b (3.1%). This is the first report of the distribution of HCV genotypes in Sri Lanka.

Rab27b association with melanosomes: dominant negative mutants disrupt melanosomal movement.

The movement of melanosomes from post-Golgi compartments to the periphery of melanocytes is known to be regulated by factors including myosin Va and at least one Rab protein, Rab27a. Mutations in the genes encoding either protein in the mouse result in a hypopigmented phenotype mimicking the human disease Griscelli syndrome. Rab27b and Rab27a share 72% identity and they belong to the same melanocyte/platelet subfamily of Rab proteins. Rab27a orchestrates the transport of melanosomes by recruitment of the actin motor, myosin Va, onto melanosomes. By contrast, the function of Rab27b has remained elusive. In this study, we found that Rab27b mRNA is present in melanocytes and demonstrated the intrinsic GTPase activity of Rab27b protein. We explored the function of Rab27b by overexpression of two dominant negative mutants as well as the wild-type Rab27b in melan-a melanocytes. Green-fluorescent-protein-tagged Rab27b colocalizes with the melanosome marker tyrosinase-related protein 1 and with myosin Va at the cell periphery, whereas Rab27b mutants do not decorate melanosomes, and melanosomes in these mutant transfected cells redistribute from cell periphery to the perinuclear region. Furthermore, transient overexpression of the dominant negative forms of Rab27b caused diminution in both numbers and length of dendrites of melan-a cells. Our results suggest that Rab27b may regulate the outward movement of melanosomes and the formation or maintenance of dendritic extensions in melanocytes.