According to a report published in eLife, the defense mechanisms that plants use to recognize and respond to a common pest, the caterpillar, evolved from a single gene that evolved over millions of years, reports Phys.org portal.
A study by Washington scientists has shown that some plants, such as soybeans, have lost this protective gene over time, but experts suggest that reintroducing the gene (through breeding, genetic engineering) may help protect the crop from crop failure.
The health status of a plant depends on the immune system it inherits. In plants, this means inheriting certain types of pattern recognition receptors that can detect various pathogens and peptides and trigger an appropriate immune response.
Inheriting the right types of pattern recognition receptors could allow plants to recognize threats and cope with diseases and pests.
To fill this gap, the team set out to identify the key evolutionary events that allowed plants to respond to a common threat: the caterpillar. Legume species, including mung beans and black-eyed peas, were already known to have a unique ability to respond to peptides produced in the mouths of caterpillars as they gnaw through plant leaves.
The scientists studied the genomes of this group of plants in detail to see if a common pattern recognition receptor called the inceptin receptor (INR) has changed over millions of years, gaining or losing the ability to recognize caterpillars.
They found that a single 28-million-year-old receptor gene perfectly matches the immune response of plants to caterpillar peptides. They also found that among the descendants of the oldest plant ancestors that first developed the receptor gene, there are several species that cannot respond to caterpillar peptides, that is, they have lost this gene.
To understand how this ancient gene acquired the ability to recognize new peptides in modern pathogens, the team used a technique called ancestral sequencing, in which they combined information from all modern receptors. genes to predict the original sequence at 28 million years old. This ancestral receptor was able to respond to caterpillar peptides. However, a slightly older version with 16 changes in the receptor sequence failed.
This genetic history, together with computer models showing how ancient and modern receptor structures may have differed, provide clues to how the receptor evolved. This suggests that more than 32 million years ago, a key new gene insert was introduced into the genome of an ancestral plant, followed by the rapid evolution of diverse forms of the new receptor. One of these forms acquired the ability to respond to caterpillar peptides, and this new ability is now shared by dozens of descendant legume species.
In the future, scientists hope to learn more about the genome-level processes that generate new receptor diversity and identify as yet unknown immune receptors in plant groups. As more and more With genomic data, such approaches would identify "missing" receptors that are useful traits to reintroduce into plants to help protect crops.