Fungi found to regulate host gene expression of a plant through the use of miRNAs

A team of researchers from Australia, the U.S. and France reports evidence of a fungus regulating host gene expression of a plant using miRNA. In their paper published in Proceedings of the National Academy of Sciences, the group describes using sRNA sequencing of data and in situ miRNA detection to learn more about the symbiotic relationship between the root fungus Pisolithus microcarpus and eucalyptus trees.

Prior research has shown that symbiotic relationships exist between living entities such as bacteria and animals or fungi and plants. And some microbes are able to transfer small RNA or microRNAs (miRNAs) to host plants to help the microbes sustain infections. In this new effort, the researchers have found an example of such transfer that benefits both the fugus and its host.

In their work, the researchers focused on a type of fungus known to infect the roots of plants. In this instance, they wanted to learn more about such infections in eucalyptus trees. To that end, they conducted sRNA sequencing on both the fungus and the trees that had been infected and also looked for instances of in situ miRNA transfer. They found that the fungus did indeed transfer some of its miRNA to the roots of the trees. And as a result of that transfer, the fungus was able to maintain its infection of trees—but more importantly, such infections actually helped the trees to do better at gaining soil nutrients. They found that trees with fungus infections removed had more trouble pulling nutrients from the soil than those that were infected. They also found that if they added more fungi to already infected trees, the tree roots performed even better than those that had been infected naturally.

A closer look at the tissues of the tree roots found that the fungus made changes to the tree's genes that coded for expression of nucleotide-binding-domain, leucine-rich repeat proteins, improving immune response and boosting health by improving soil nutrient processing. They conclude that microRNAs can have a major impact on mutualism between microbes and plants.