Characterization of influx and efflux silicon transporters and understanding their role in the osmotic stress tolerance in finger millet (Eleusine coracana (L.) Gaertn.).

Over the last decade, silicon (Si) has been widely accepted as a beneficial element for plant growth. The advantages plant derives from the Si are primarily based on the uptake and transport mechanisms. In the present study, the Si uptake regime was studied in finger millet (Eleusine coracana (L). Gaertn.) under controlled and stress conditions. The finger millet can efficiently uptake Si and accumulate it by more than 1% of dry weight in the leaf tissues, thus categorized as a Si accumulator. Subsequent evaluation with the single root assay revealed a three-fold higher Si uptake under osmatic stress than control. These results suggest that Si alleviated the PEG-induced stress by regulating the levels of osmolytes and antioxidant enzymes. Further, to understand the molecular mechanism involved in Si uptake, the Si influx (EcoLsi1 and EcoLsi6) and efflux transporters (EcoLsi2 and EcoLsi3) were identified and characterized. The comparative phylogenomic analysis of the influx transporter EcoLsi1 with other monocots revealed conserved features like aromatic/arginine (Ar/R) selectivity filters and pore morphology. Similarly, Si efflux transporter EcoLsi3 is highly homologous to other annotated efflux transporters. The transcriptome data revealed that the expression of both influx and efflux Si transporters was elevated due to Si supplementation under stress conditions. These findings suggest that stress elevates Si uptake in finger millet, and its transport is also regulated by the Si transporters. The present study will be helpful to better explore Si derived benefits in finger millet.

An insight into the role of silicon on retaliation to osmotic stress in finger millet (Eleusine coracana (L.) Gaertn).

Finger millet, a vital nutritional cereal crop provides food security. It is a well-established fact that silicon (Si) supplementation to plants alleviates both biotic and abiotic stresses. However, precise molecular targets of Si remain elusive. The present study attempts to understand the alterations in the metabolic pathways after Si amendment under osmotic stress. The analysis of transcriptome and metabolome of finger millet seedlings treated with distilled water (DW) as control, Si (10 ppm), PEG (15%), and PEG (15%) + Si (10 ppm) suggest the molecular alterations mediated by Si for ameliorating the osmotic stress. Under osmotic stress, uptake of Si has increased mediating the diversion of an enhanced pool of acetyl CoA to lipid biosynthesis and down-regulation of TCA catabolism. The membrane lipid damage reduced significantly by Si under osmotic stress. A significant decrease in linolenic acid and an increase of jasmonic acid (JA) in PEG + Si treatment suggest the JA mediated regulation of osmotic stress. The relative expression of transcripts corroborated with the corresponding metabolites abundance levels indicating the activity of genes in assuaging the osmotic stress. This work substantiates the role of Si in osmotic stress tolerance by reprogramming of fatty acids biosynthesis in finger millet.

In Vitro Callus Induction and Plant Regeneration from Stem Explants of Ceropegia noorjahaniae, a Critically Endangered Medicinal Herb.

An efficient protocol has been developed for in vitro regeneration of a large number of plantlets of Ceropegia noorjahaniae Ansari via indirect organogenesis from stem explants excised from in vitro-germinated seedlings. The callus was efficiently induced from the stem explants using Murashige and Skoog (MS) medium supplemented with auxins and their combinations. The highest number of shoots (16.0 ± 0.2) and shoot length (5.5 ± 0.1 cm) was achieved when the callus was subcultured to MS medium supplemented with 6-benzylaminopurine, BAP (2.0 mg/l) and indole-3-acetic acid, IAA (0.2 mg/l). The in vitro-developed shoots were rooted well in half-strength MS medium supplemented with 1.0 mg/l of indole-3-butyric acid (IBA) and 0.3 mg/l of α-naphthalene acetic acid (NAA). The plantlets were successfully hardened with 82 % survival rate. This is the first report on the regeneration of plants through indirect shoot organogenesis from stem derived calli of C. noorjahaniae.

Micropropagation and non-steroidal anti-inflammatory and anti-arthritic agent boswellic acid production in callus cultures of Boswellia serrata Roxb.

Micropropagation through cotyledonary and leaf node and boswellic acid production in stem callus of a woody medicinal endangered tree species Boswellia serrata Roxb. is reported. The response for shoots, roots and callus formation were varied in cotyledonary and leafy nodal explants from in vitro germinated seeds, if inoculated on Murshige and Skoog's (MS) medium fortified with cytokinins and auxins alone or together. A maximum of 8.0 ± 0.1 shoots/cotyledonary node explant and 6.9 ± 0.1 shoots/leafy node explants were produced in 91 and 88 % cultures respectively on medium with 2.5 µM 6-benzyladenine (BA) and 200 mg l(-1) polyvinylpyrrolidone (PVP). Shoots treated with 2.5 µM IBA showed the highest average root number (4.5) and the highest percentage of rooting (89 %). Well rooted plantlets were acclimatized and 76.5 % of the plantlets showed survival upon transfer to field conditions. Randomly amplified polymorphic DNA (RAPD) analysis of the micropropagated plants compared with mother plant revealed true-to-type nature. The four major boswellic acid components in calluses raised from root, stem, cotyledon and leaf explants were analyzed using HPLC. The total content of four boswellic acid components was higher in stem callus obtained on MS with 15.0 µM IAA, 5.0 µM BA and 200 mg l(-1) PVP. The protocol reported can be used for conservation and exploitation of in vitro production of medicinally important non-steroidal anti-inflammatory metabolites of B. serrata.