How genetic division helped plants overcome polluted soil

Phytochelatin complexes (PCSs) produce phytochelatins – small cysteine-rich peptides that bind and neutralize toxic metal ions such as cadmium and arsenic. These molecules act as the plant’s natural detoxification system, trapping harmful elements in vacuoles to prevent cell damage.

Although previous studies have explored individual PCS genes in model plants such as Arabidopsis thaliana (AtPCS1, AtPCS2), the broader picture of how PCS genes diversify across plant evolution has remained unclear.

Without understanding this evolutionary history, it has been difficult to explain why plants vary so much in their tolerance to metals. Building on these challenges, researchers sought to uncover how gene duplication and functional divergence shape PCS evolution across plant genomes.

A research team from Fondazione Edmund Mach and the University of Pisa has traced the evolutionary origin of metal detoxification machinery in plants.

Their findingspublished in Horticulture researchThey reveal that duplication of long-overlooked PCS genes occurred early in the evolution of flowering plants.

By combining genome-wide phylogenetic reconstruction with laboratory and plant-level experiments, the researchers discovered how this redundancy – the split into D1 and D2 lineages – enabled plants to fine-tune their biochemical defense against heavy metal-induced stress.

The study analyzed more than 130 complete plant genomes to map the evolutionary journey of PCS genes. The researchers discovered an ancient duplication, dubbed “D duplication,” which appeared during the early diversification of dicots and has been preserved ever since. This event split the PCS genes into two families: D1 and D2.

To explore their functions, the team isolated MdPCS1/MdPCS2 from apple and MtPCS1/MtPCS2 from the medicinal barrel and introduced them into Arabidopsis thaliana mutants that lack native PCS activity. Laboratory tests revealed that D2-type PCS enzymes were significantly more active than their D1 counterparts, showing an enhanced ability to synthesize phytochelatins and bind cadmium and arsenic.

In living plants, D2 genes conferred stronger growth recovery and higher tolerance under metal stress, while D1 genes maintained general thiol homeostasis and moderate detoxification capacity. Sequence analysis identified two key amino acid residues most likely responsible for their functional difference.

The results suggest that both types of genes were retained because their complementary roles ensured efficient toxin removal – a remarkable example of evolutionary fine-tuning that continues to protect modern crops.

“Our findings reveal how evolution has improved a vital survival mechanism,” said Dr. Claudio Farotto, author of the study.

“The two genetic versions of PCS have coexisted for over a hundred million years because they complement each other – D1 provides stability, while D2 provides energy. This dual system gives plants the flexibility to adapt to a range of mineral challenges. It is a perfect example of how ancient genetic innovation continues to shape the resilience of plants today.”

This discovery not only deepens our understanding of plant evolution, but also opens new paths to sustainable agriculture. By targeting PCS gene expression or transferring D2-type PCS activity to susceptible crops, breeders can create varieties that thrive in contaminated soil while reducing heavy metal accumulation in edible parts.

Such genetic insights could also enhance phytoremediation strategies, where plants are used to clean up polluted environments.

As the world confronts rising soil pollution, understanding how plants evolved tolerance to toxic metals provides scientific inspiration and practical tools for a safer agricultural future.