NITROGEN LIMITATION ADAPTATION functions as a negative regulator of Arabidopsis immunity

Background: Phosphorus is an important macronutrient required for plant growth and development. It is absorbed through the roots in the form of inorganic phosphate (Pi). To cope with Pi limitation, plants have evolved an array of adaptive mechanisms to facilitate Pi acquisition and protect them from stress caused by Pi starvation. The NITROGEN LIMITATION ADAPTION (NLA) gene plays a key role in the regulation of phosphate starvation responses (PSR), its expression being regulated by the microRNA miR827. Stress caused by Pi limiting conditions might also affect the plant response to pathogen infection. However, cross-talk between phosphate signaling pathways and immune responses remains unclear. Results: In this study, we investigated whether NLA plays a role in Arabidopsis immunity. We show that loss-of-function of NLA and MIR827 overexpression causes an increase in phosphate (Pi) content which results in resistance to infection by the fungal pathogen Plectosphaerella cucumerina. The nla mutant plants accumulated callose in their leaves, a response that is also observed in wild-type plants that have been treated with high Pi. We also show that pathogen infection and treatment with fungal elicitors is accompanied by transcriptional activation of MIR827 and down-regulation of NLA. Upon pathogen challenge, nla plants exhibited higher levels of the phytoalexin camalexin compared to wild type plants. Camalexin level also increases in wild type plants treated with high Pi. Furthermore, the nla mutant plants accumulated salicylic acid (SA) and jasmonic acid (JA) in the absence of pathogen infection whose levels further increased upon pathogen. Conclusions: This study shows that NLA acts as a negative regulator of Arabidopsis immunity. Overaccumulation of Pi in nla plants positively affects resistance to infection by fungal pathogens. This piece of information reinforces the idea of signaling convergence between Pi and immune responses for the regulation of disease resistance in Arabidopsis.

Enrichment of Therapeutically Significant Flavonolignans of Silybum Marianum in Vegetative Parts by Applying Fungal Elicitors, Methyl Jasmonate and Silver Nanoparticles as Elicitor in Hydroponic Culture

Introduction: Medicinal plants are being used to treat several diseases for many decades and this is an ancient method to treat the patients. Herbal plant Silybum marianum found most effective one to cure liver disorders. This plant produces silymarin which is a secondary metabolite and have hepatoprotective properties. Silymarin is a mixture of flavonolignans (silybin A, silybin B, isosilybin A isosilybin B, silychristin, silydianin apigenin 7-D glucose and taxifolin) that has antiviral, antibacterial, antifungal and antiallergenic properties. Therefore, the excessive production of silymarin is necessary to cure different types liver disorders, so the present study executed to boost up production of Silymarin flavonolignans in vegetative parts of the Silybum marianum plant by using different elicitors. Materials and Methods: In the present study, elicitation technique in hydroponics system was used to enhance the production of pharmacologically active flavonolignans in Silybum marianum. Fungal elicitors prepared from lyophilized Aspergillus niger biomass, methyl jasmonate, silver nanoparticles and combination of silver nanoparticles and methyl jasmonate were added (0.2g/l), (100µM/l), (1 ppm) and (100µM/lppm) in hydroponics with Hoagland’s solution in hydroponics to enhance the production of flavonolignans of Silybum marianum. Controls were also set for each treatment. Plants were harvested after 72 hours of introduction of elicitors. High performance liquid chromatography technique was used for analytical purpose. Four solvents (methanol, acetonitrile, chloroform and 2% Trifloro acetic acid) were used in HPLC. Column was C18 and run time of sample was 1 hour. Silybum marianum’s seed extract was used as a standard. Extract of control and treated plants were run on the same polarity in HPLC. Results: Results showed that after elicitation significant increase was observed in production of silymarin’s flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B and apigenin 7-D glucose) in vegetative part of the plant but rate of production was different for each elicitor, fungal elicitors prepared from lyophilized Aspergillus niger biomass proved best among all treatments.

Biotic and abiotic stress roles in drugs production through in vitro approaches in plants – a review

Plant metabolic engineering is a modern discipline that promises to create opportunities in pharmaceutical industries to produce and biomedicine. Over the long period natural and synthetic plant hormones have had tremendous implications in callus/cell culture /suspension/ for secondary metabolites production (SMs). Generally, SMs plays a vital fundamental role in protecting the plant from biotic and abiotic attacks to which it may be subjected. This review article focused on the relationship between various factors related to the drug production. In medicinal plants, in vitro studies, based on biotic factors such as fungal/endo-phytic fungal elicitors/microbe-derived exogenous elicitor yeast extract (YE) were cross checked with the abiotic six factor groups, including auxins and cytokinins, gamma radiation, lights, temperature, carbon sources, photoperiods, precursor chemicals and plant metabolic enzymes. Moreover, key enzymes and gene networks can serve as a resource to selected potential targets for specific SMs production. This is the first review to describe the light factors needed for the SM production, which has favorable role for SMs. We envisage that the researcher can design how to modulate the stress factors in terms of drug improvement from medicinal plants.

Pathogen Inducible cis-acting Elements of Synthetic Promoters in Plants-review

Synthetic pathogen inducible promoters are used for the improvement and application of transgenic techniques in research and to increase agriculture production. The promoter contains specific cis-regulatory elements (W box, GCC box, Box S and D box) which induce anti pathogen molecular cascades. Insertion of dimerized form of cis acting elements at upstream region of promoter in promoter probe vector drives the expression of resistance gene or reporter gene. The expression indicates that synthetic promoters are responded to fungal elicitors. Expression of resistance restrict to infection sites which boost disease resistance in plants.