Study on Folate Binding Domain of Dihydrofolate Reductase in Different Plant species and Human beings

Towards establishment of a plant-based model to assess the novel anti-cancerous lead molecule(s): An in silico, in vivo and in vitro assessment of some potential anti-cancerous drugs on Lathyrus sativus L

The drug development process is one of the important aspects of medical biology. The classical lead identification strategy in the way of drug development based on animal cell is time-consuming, expensive and involving ethical issues. The following study aims to develop a novel plant-based screening of drugs. Study shows the efficacy of certain anti-cancerous drugs (Pemetrexed, 5-Fluorouracil, Methotrexate, Topotecan and Etoposide) on a plant-based (Lathyrus sativus L.) system. Two important characteristics of cancer cells were observed in the colchicine-treated polyploid cell and the callus, where the chromosome numbers were unusual and the division of cells were uncontrolled respectively. With increasing concentration, the drugs significantly reduced the mitotic index, ploidy level and callus growth. Increasing Pemetrexed concentration decreased the plant DHFR activity. A decrease in total RNA content was observed in 5-FU and Methotrexate with increasing concentrations of the drugs. Etoposide and Topotecan inhibited plant topoisomerase II and topoisomerase I activities, which was justified through plasmid nicking and comet assay, respectively. Molecular and biochemical study revealed similar results to the animal system. The in silico study had been done, and the structural similarity of drug binding domains of L. sativus and human beings had also been established. The binding site of the selected drugs to the domains of plant target proteins was also determined. Experimental results are significant in terms of the efficacy of known anti-cancerous drugs on the plant-based system. The proposed assay system is a cost-effective, convenient and less time-consuming process for primary screening of anti-cancerous lead molecules.

TOR coordinates nucleotide availability with ribosome biogenesis in plants

TARGET OF RAPAMYCIN (TOR) is a conserved eukaryotic Ser/Thr protein kinase that coordinates growth and metabolism with nutrient availability. We conducted a medium-throughput functional genetic screen to discover essential genes that promote TOR activity in plants, and identified a critical regulatory enzyme, cytosolic phosphoribosyl pyrophosphate (PRPP) synthetase (PRS4). PRS4 synthesizes cytosolic PRPP, a key upstream metabolite in nucleotide synthesis and salvage pathways. We found that prs4 knockouts are embryo-lethal in Arabidopsis thaliana, and that silencing PRS4 expression in Nicotiana benthamiana causes pleiotropic developmental phenotypes, including dwarfism, aberrant leaf shape, and delayed flowering. Transcriptomic analysis revealed that ribosome biogenesis is among the most strongly repressed processes in prs4 knockdowns. Building on these results, we discovered that TOR activity is inhibited by chemical or genetic disruption of nucleotide biosynthesis, but that this effect can be reversed by supplying plants with nucleobases. Finally, we show that TOR transcriptionally promotes nucleotide biosynthesis to support the demands of ribosomal RNA synthesis. We propose that TOR coordinates ribosome biogenesis with nucleotide availability in plants to maintain metabolic homeostasis and support growth.