Biology subjects

Tiwari, N.

Publications and source records attributed to Tiwari, N..

3 recordsLinked to original sources

bioRxiv2020

Molecular phylogenetics and character evolution in Haplanthodes (Acanthaceae), an endemic genus from peninsular India.

Haplanthodes (Acanthaceae) is an Indian endemic genus with four species. It is closely related to Andrographis which is also mainly distributed in India. Haplanthodes differs from Andrographis by the presence of cladodes in the inflorescences, sub actinomorphic flowers, stamens included within the corolla tube, pouched stamens and oblate pollen grains. To understand the phylogenetic relationship of Haplanthodes with Andrographis and Haplanthus, another related genus, we used four plastid markers, matK, rbcL, psbA-trnH and trnGR to construct a molecular phylogeny. Our results established the monophyly of this genus and revealed a sister relationship to Andrographis and Haplanthus. Further, to understand the historical biogeography of the genus, we inferred the divergence time and performed ancestral area reconstruction. Our analyses suggest that Haplanthodes has evolved during Late Miocene 5.85 Ma [95%HPD: 2.18-10.34 Ma] in peninsular India where it might have shared a common ancestor with Andrographis. To understand character evolution, the ancestral states of important morphological characters were inferred based on the equal rate model and discussed. The generic status of Haplanthus is not resolved due to incomplete sampling.

evolutionary biology↗

bioRxiv2020

Ratio of hydrophobic-hydrophilic and positive-negative residues at lipid-water-interface influences surface expression and channel-gating of TRPV1

During evolution, TRPV1 has lost, retained or selected certain residues at Lipid-Water-Interface (LWI) and formed specific patterns there. The ratio of "hydrophobic-hydrophilic" and "positive-negative charged" residues at the inner LWI remains conserved throughout vertebrate evolution and play important role in regulating TRPV1 trafficking, localization and functions. Arg575 is an important residue as Arg575Asp mutant has reduced Capsaicin-sensitivity, surface expression, colocalization with lipid-raft markers, cell area, and increased cell lethality. This lethality is due to the disruption of the ratio between positive-negative charges there. Such lethality can be rescued by either using TRPV1-specfic inhibitor 5-IRTX or by restoring the positive-negative charge ratio at that position, i.e. by introducing Asp576Arg mutation in Arg575Asp backbone. We propose that Arg575Asp mutant confers TRPV1 in a "constitutive-open-like" condition. These findings have broader implication in understanding the molecular basis of thermo-gating and channel-gating and the microenvironments involved in such process that goes erratic in different diseases.

cell biology↗

bioRxiv2020

Eocene origin, Miocene diversification and intercontinental dispersal of the genus Drosera (Droseraceae)

Resolving the evolutionary history of plant carnivory is of great interest to biologists throughout the world. Among the carnivorous plants, Genus Drosera (Droseraceae) is highly diverse with a wide pantropical distribution. Despite being a group of interest for evolutionary biology studies since the time of Charles Darwin, the historical biogeography of this group remains poorly understood. In this study, with an improved species sampling from Genbank, we present a reanalyzed phylogenetic hypothesis of the genus Drosera. We developed a dated molecular phylogeny of Drosera from DNA sequences of nuclear ITS and chloroplast rbcL genes. Divergence times were estimated on the combined dataset using an uncorrelated lognormal relaxed clock model and a known fossil calibration implemented in BEAST. The maximum clade credibility tree was then used for ancestral range estimations using DEC+J model implemented in BioGeoBEARS. Our analysis suggests that Drosera evolved during the Mid Eocene 36 Ma [95% HPD: 49.5-26] and have diversified and dispersed from the late Miocene onwards. Ancestral areas estimated using the DEC+J models suggest an African origin followed major radiation within Australia. Diversification in Drosera is temporally congruent with the prevailing drier conditions during the Miocene. From Miocene, grasslands and open habitats dominated across continents and might have provided ecological opportunities for their dispersal and diversification. Several long-distance dispersals and range extensions and in situ radiations coinciding with the evolution of drier conditions can explain their extant distribution across continents. Overall our data set provides fresh insights into the biogeographic factors that shaped the origin and evolution of the genus Drosera.

evolutionary biology↗