A novel broad-spectrum antifungal protein has been identified by a research group led by Dr. Gopaljee Jha at the New Delhi- based National Institute of Plant Genome Research (NIPGR) -An autonomous Institute of Department of Biotechnology, Govt. of India. The results were published in the journal Nature Communications.
Fungal pathogens have been a challenge for sustainable agriculture and they have been behind death and disability in humans, wildlife extinctions, and population declines. By and large, it is very difficult to control fungal diseases and globally there have been urgent thrust to devise newer strategies to control them.
The breakthrough was heralded by Dr. Jha’s team when they isolated a novel bacterium Burkholderia gladioli strain NGJ1 from healthy rice seedling which exhibits broad spectrum fungal eating property (the phenomenon known as mycophagy).The researchers observed that bacterium was killing fungal cells to utilize their metabolites for its own growth and survival.
It is very interesting how a bacterium (smaller in size) can feed on fungi, which is relatively much bigger in size.
“Considering phenotype associated with mycophagy, we expected that NGJ1 would perform as a better biocontrol agent than other antifungal bacteria. Due to its mycophagous property, the bacterium can not only prevent fungal growth but can eradicate fungal biomass as it utilizes them as a source of nutrients. Indeed treatment of NGJ1 was found to prevent the disease-causing ability of Rhizoctonia solani, the causal agent of sheath blight disease of rice,” said Dr. Jha.
Scientists have always believed that phages are bacterial predators and upon induction, they can lyse bacterial cells. However, Dr. Jha’s group observed that the NGJ1 has made its phage inactive (prophage) and deputes one of the prophage tail-like proteins (Bg_9562) to forage over fungi.Through series of experimentation, the group could demonstrate that the NGJ1 utilizes one of its phage proteins to eat fungi.
The researchers tested the purified Bg_9562 protein to check the broad spectrum antifungal activity. Strikingly, the antifungal activity was observed against several economically important phytopathogens, such as Rhizoctonia solani (rice sheath blight pathogen), Magnaportheoryzae (rice blast pathogen), Fusarium oxysporum (pathogenic to various plants), Aschocytarabiei (chickpea blight pathogen), Venturiainaequalis (apple scab pathogen) and Candida albicans (causes Candidiasis in humans).
“This is the first report stating that a potential Type-3 secretion is required during the Bacterial-Fungal interaction. This opens up a new area of basic science research,” said Dr.Durga Madhab Swain,(One of the first authors in this paper).
“Considering broad-spectrum antifungal activity, it is being proposed that the protein could be utilized to control fungal diseases of plants as well as humans/animals. For example, a formulation using this protein can be sprayed over the agricultural field to control various fungal diseases at one go or an ointment based on this protein can be used to treat fungal infections of animals/humans. Furthermore, the Bg_9562 gene can itself be used as a transgene to develop broad-spectrum fungal disease resistant plants, which is need of the hour,” said the study leader Dr. Jha.
The present study not only showcases high-end basic science research, but it has opened up various translational applications in controlling fungal diseases.
Dr. Jha says that it has been a gigantic task and various researchers (Durga, Sunil, Isha, Rahul, Rajeev, Srayan, Joyati) have worked day and night to identify the molecular basis of bacterial mycophagy.
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