Discovery of vital plant gene boosts hope for improved crops

Scientists make a breakthrough after years spent attempting to crack the genetic mechanisms behind the symbiotic relationship with plants and mycorrhizal fungi.

A multi-institute team, led by Oak Ridge National Laboratory (ORNL; TN, USA), have discovered a specific gene responsible for mediating the symbiosis between plants and the soil fungi, mycorrhiza.

Mycorrhizal fungi are found to be associated with an estimated 80% of plant species’ roots, often encasing them in a structure known as a fungal sheath. The fungi are essential for aiding many important plant processes as their mycelia are much finer than plant roots, allowing them to extend further into soil. This symbiotic relationship increases the plant’s ability to: uptake water, absorb nutrients and signal. In return, the mycorrhiza receive carbon from the plant.

Supported by the Department of Energy’s Office of Science and Center for Bioenergy Innovation, the work was a collaboration between ORNL, the University of Lorraine (France) and the HudsonAlpha Institute for Biotechnology in Alabama (AL, USA). ORNL and their partner institutions have spent 10 years investigating techniques to improve bioenergy and feedstock crops.

“If we can make Arabidopsis interact with this fungus, then we believe we can make other biofuel crops like switchgrass, or food crops like corn also interact and confer the exact same benefits.

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Scientists investigated symbiosis between a certain species of Populus, common name Poplar, and the fungus Laccaria bicolor By utilizing supercomputing resources at the Oak Ridge Leadership Computing Facility (TN, USA) in conjunction with genomic sequences produced at the Joint Genome Institute (CA, USA), the team was able to identify a candidate gene that codes for receptor protein PtLecRLK1 – a G-type lectin receptor-like kinase.

To validate the role of PtLecRLK1, the researchers created a genetically engineered Arabidopsis that produced the non-native PtLecRLK1 protein.   The Arabidopsis plant is usually resistant to L. Bicolar and even sees it as a hazard. The Arabidopsis was treated with L. Bicolar and the fungus cultivated on the plant’s roots forming a fungal sheath, suggesting that the inclusion of PtLecRLK1 was enough to confer the symbiotic relationship.

“We showed that we can convert a non-host into a host of this symbiont,” explained Wellington Muchero (ORNL). “If we can make Arabidopsis interact with this fungus, then we believe we can make other biofuel crops like switchgrass, or food crops like corn also interact and confer the exact same benefits. It opens up all sorts of opportunities in diverse plant systems. Surprisingly, one gene is all you need.”

This discovery infers the potential to develop bioenergy and food crops that require lower levels of fertilizer, can withstand pathogens and pests more effectively, and are larger and more bountiful. With the effects of climate change being felt more than ever, the ability to engineer plants that can withstand harsher growing conditions, such as drought, is an attractive prospect.