Plant prickles need not be a thorn in the side of horticulturalists and farmers

• Gene editing can eliminate plant prickles
• The approach is promising for roses, where labour intensive manual removal of prickles is a common practice
• Removal of prickles will also mean easier handling of crops like aubergines

In a breakthrough discovery, scientists have found that the same ancient gene family is responsible for the evolution and loss of prickles (referred to as thorns in the case of roses) across many plants, despite millions of years of evolutionary separation.

This discovery could revolutionise crop improvement by enabling the development of prickle-free varieties in plants such as aubergines and roses.

Prickles have evolved independently in species across the plant kingdom, predominantly to ward off herbivores. Until now, it has not been clear how these protrusions found on flowering plants (angiosperms) such as roses, as well as on certain aubergine varieties, are so frequently present in unrelated species.

The study, conducted by a global team of evolutionary biologists and geneticists, reveals that mutations in a specific gene responsible for cytokinin hormone production have led to the repeated loss of prickles in diverse plant species over millions of years.

When lead author, James Satterlee, researcher at Cold Spring Harbor Laboratory, USA, began analysing aubergine plants, he identified a gene family called LOG, or LONELY GUY. James discovered that certain LOG mutations eliminated the prickles in some aubergine species.

He and his team then referred to the expertise of collaborators around the world, which included Dr Sandra Knapp, Research Botanist at the Natural History Museum and specialist in the nightshade family, Solanaceae, which includes aubergines, tomatoes and potatoes. Sandy’s and her colleagues’ extensive phylogenetic research in understanding the family tree of the genus, as well as knowing on which species prickles occur, enabled the scientists investigating the gene to know where to look and which plants to sequence.

The researchers then conducted a detailed genetic analysis of Solanum species, including cultivated and wild varieties of aubergines. By sequencing the genomes and identifying specific mutations in the LOG gene, they were able to correlate these genetic changes with the presence or absence of prickles. Additionally, they explored the broader evolutionary history of this gene across multiple plant lineages, associating prickles with LOG-related genes in about 20 species.

Dr Sandra Knapp comments, "This incredible research shines a light on the extraordinary capabilities of plant bodies. In the same way we do with humans, recognising the difference between plants as populations, to them as families, or individuals, allows us to unearth incredible plant knowledge on a deep evolutionary level.

“When we combine this understanding with the advanced molecular biology used in this study, we can answer real world problems. Removing prickles could have huge ramifications for the supply chain of eggplants, as prickles can damage fruits during transportation, and may even mean that new crops, which are currently too prickly to handle, may be introduced into our shopping baskets."

The team have since used the cutting-edge gene editing techniques to engineer prickle-free plants, such as desert raisins, a foraged berry native to Australia. Researchers in France were able to suppress prickles in roses.

As well as the practical applications, the study also has big implications for understanding convergent evolution of traits that occur across the natural world.

The study, Convergent evolution of plant prickles by repeated gene co-option over deep time, is now available on Science. DOI: 10.1126/science.ado1663

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