Researchers at the University of Hyderabad (UoH) have used Nanotechnology to boost Plant Immunity. They have developed a new nanotechnology tool to increase bioavailability and efficiency, reducing the quantity of the harpin required to boost immunity, and enhanced penetrability of protein to easily access the site-of-action. Research team lead by Prof. Appa Rao Podile, faculty in the Department of Plant Sciences, School of Life Sciences and presently the Vice-Chancellor of UoH has used a nanotechnology-based approach to deliver the bioactive harpin to right location in the plants i.e., chloroplasts, to induce immunity against that could affect broad-spectrum of microbial pathogens. Dr. Sravana Sandhya, who worked with Prof. Podile in a Department of Biotechnology, Government of India, funded project has devised an innovative approach which has multiple advantages.

The detailed benefits of the use of this innovative approach will now appear in a high impact journal entitled Carbohydrate Polymers published by Elsevier, as the editor has just conveyed the acceptance for publication of this work. These findings constitute a major step towards plant immunization.

L to R Post-Doc Fellow Dr. T Swaroopa Rani, PhD Scholar Shri Rajesh Rao Maddu, Prof. Appa Rao Podile and Dr. Sravana Sandhya

L to R Post-Doc Fellow Dr. T Swaroopa Rani, PhD Scholar Shri Rajesh Rao Maddu, Prof. Appa Rao Podile and Dr. Sravana Sandhya

In the meanwhile, Prof. Podile’s group has tied up with Dr. K.R.K. Reddy, Director, Sri Bioaesthetics Pvt. Ltd, to produce both harpin and H-CSNPs on a pilot scale and test their efficiency in four different crops against different foliar diseases. This joint proposal was short-listed by the Department of Science and Technology, Government of India under IMPRINT-2 to develop a nanoparticle-based delivery system as prophylactic foliar spray for crop protection. Industry partner also supports 10% of project costs under this programme. This support under IMPRINT-2, when available, will allow Prof. Podile and Dr. Reddy to produce and test these nanoparticles on large scale, besides testing their toxicity to humans before this technology could become commercially available.

Harpin, an elicitor from a plant pathogenic bacterium called Pseudomonas syringae pv. syringae, induces systemic acquired resistance in non-host plants, providing resistance to phytopathogens. Poor assimilation of harpin is a major constraint in foliar application as biopesticide. Prof. Podile and Dr. Sandhya, therefore, prepared harpin-loaded chitosan nanoparticles (H-CSNPs) to improve permeability and bio-availability of harpin in tomato. The innovation in this approach is not limited to the use of bioactive compound to induce resistance. The unique delivery system made use of chitosan in the form of nanoparticles, which is easily biodegradable and itself is a known inducer of immunity in plants. The combined effect of harpin and chitosan and their biodegradability, coupled with activation of well-known defense pathways of plants make this a unique approach, hitherto not known for crop protection.

H-CSNPs showed high encapsulation efficiency, improved stability and bioavailability of harpin. Treatment with H-CSNPs resulted in decreased Rhizoctonia solani (fungal pathogen of tomato) infection. Subcellular changes in tomato were studied by Sandhya and Podile that allowed them to explain that the transcripts of several genes involved in defense response were differentially expressed in harpin, CSNPs and H-CSNPs treatments. An unexpected outcome of this work was that the group had to investigate the path of movement of CSNPs into the cell. First time they have demonstrated that the harpin is localized into chloroplast, the organ where photosynthetic process takes place in plants.

Prof. Appa Rao Podile and the members of his research team gratefully acknowledge the high-end research facilities created mostly by the DST and DBT, at the University of Hyderabad, under Centre for Nanotechnology, PURSE and FIST grants that made it possible to take up such advanced research. Prof. Podile specially thanks the DBT for the major grant support given under the nanotechnology initiative to his lab.

BACKGROUND:
Harpin from Erwinia amylovora was the first harpin-biopesticide registered for its application in crop-protection from several fungal, bacterial and viral diseases. Harpin as a novel biopesticide was permitted by US environmental protection agency, attracted the global market with its potential as eco-friendly peptide for crop-protection. A major constraint in the utilization of harpin as bio-pesticide is its poor bioavailability to the plant cell upon foliar application. Due to the unique architecture of leaves, only a few harpin molecules could interact with the putative receptors. Therefore, a large amount of harpin is required for spray-application. Against this background, UoH researchers developed a new nanotechnology tool to increase bioavailability and efficiency, reducing the quantity of the harpin required to boost immunity, and enhanced penetrability of protein to easily access the site-of-action.

FINDINGS:
Agricultural production is mainly challenged by infectious microbes like fungi, bacteria and viruses or by insects. Synthetic chemical fungicides and pesticides are used to control plant diseases. Since these chemicals are often not degraded easily in the soil, they exert damaging effect on environment. Researchers at Department of Plant Sciences, University of Hyderabad developed an innovative approach to use bio-active protein called harpin, taken from a phyto pathogenic bacterium, which biodegradable. The approach is akin to the immunization of humans using the killed or attenuated forms of pathogen for subsequent protection against the same pathogen.

HIGHLIGHTS:
• Harpin-loaded chitosan nanoparticles (H-CSNPs) were prepared for foliar application

• Foliar application H-CSNPs reduced the severity of Rhizoctonia solani infection in tomato

• Transcripts involved in defense and JA signalling were altered on H-CSNPs treatment

• Entry of CSNPs and localization of harpin in leaves were tracked using sophisticated laser confocal microscopy.

Picture Courtesy : Mahesh Gokara

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