Enhanced production of withaferin-A in shoot cultures of Withania somnifera (L) Dunal

Withania somnifera (L) Dunal, commonly known as ashwagandha or Indian ginseng, is the source of large number of pharmacologically active withanolides. Withaferin-A (WS-3), a major withanolide of W. somnifera, has been proven to be an effective anti-cancer molecule. In this study, a liquid culture system for shoot proliferation, biomass accumulation and withaferin-A production of an elite accession (AGB002) of W. somnifera was investigated. The nodal explants cultured on Murashige and Skoog (MS) semi-solid medium supplemented with various concentrations of 6-benzyl adenine (BA) and Kinetin (Kn) elicited varied responses. The highest number of regenerated shoots per ex-plant (35?±?3.25) and the maximum average shoot length (5.0?±?0.25 cm) were recorded on MS medium supplemented with BA (5.0 μM). The shoots were further proliferated in half and full strength MS liquid medium supplemented with the same concentration BA. It was interesting to note that shoots cultured on MS half strength liquid medium fortified with 4 gL-1 FW (fresh weight) shoot inoculum mass derived from 5 week old nodal explants of W. somnifera showed highest accumulation of biomass and withaferin A content in 5 weeks. Withaferin A was produced in relatively high amounts (1.30 % and 1.10 % DW) in shoots cultured in half and full strength MS liquid media respectively as compared to natural field grown plants (0.85 % DW). A considerable amount of the withaferin A was also excreted in the culture medium. Successful proliferation of shoots in liquid medium and the synthesis of withaferin A in vitro opens new avenues for bioreactor scale-up and the large-scale production of the compound.     

DNA methyltransferase homologue TRDMT1 in Plasmodium falciparum specifically methylates endogenous aspartic acid tRNA

In eukaryotes, cytosine methylation regulates diverse biological processes such as gene expression, development and maintenance of genomic integrity. However, cytosine methylation and its functions in pathogenic apicomplexan protozoans remain enigmatic. To address this, here we investigated the presence of cytosine methylation in the nucleic acids of the protozoan Plasmodium falciparum. Interestingly, P. falciparum has TRDMT1, a conserved homologue of DNA methyltransferase DNMT2. However, we found that TRDMT1 did not methylate DNA, in vitro. We demonstrate that TRDMT1 methylates cytosine in the endogenous aspartic acid tRNA of P. falciparum. Through RNA bisulfite sequencing, we mapped the position of 5-methyl cytosine in aspartic acid tRNA and found methylation only at C38 position. P. falciparum proteome has significantly higher aspartic acid content and a higher proportion of proteins with poly aspartic acid repeats than other apicomplexan pathogenic protozoans. Proteins with such repeats are functionally important, with significant roles in host-pathogen interactions. Therefore, TRDMT1 mediated C38 methylation of aspartic acid tRNA might play a critical role by translational regulation of important proteins and modulate the pathogenicity of the malarial parasite.     

Prokaryotic communities adapted to microhabitats on the Indian lotus (Nelumbo nucifera) growing in the high-altitude urban Dal Lake

International Microbiology - Indian lotus (Nelumbo nucifera) is one of the dominant aquatic plants cultivated in Dal Lake, situated at 1586 m above mean sea level (MSL) in the northeast of...