# Convergent evolution increases boron transport through SNPs and tandem duplications at BOR1 and BOR2 in Arabidopsis thaliana

## TL;DR

Plants from boron-poor volcanic islands evolved similar ways to boost boron uptake, offering clues for developing resilient crops.

## Contribution

Discovery of convergent evolution in BOR1 and BOR2 genes through SNPs and duplications in Arabidopsis thaliana.

## Key findings

- Multiple populations evolved increased leaf boron via mutations in BOR1 and BOR2.
- Tandem duplications at BOR1 arose independently in different populations.
- Combining GWAS and recombinant populations improves detection of genetic variants in natural settings.

## Abstract

Boron is an essential nutrient for plant growth, but many soils lack sufficient amounts, limiting crop production worldwide. To understand how plants adapt to boron-deficient environments, we studied wild mustard plants that naturally colonized volcanic islands, where boron is typically scarce. We identified a case of convergent evolution, wherein different plant populations independently evolved to increase boron concentrations in their leaves through distinct genetic changes in genes controlling boron transport. This finding reveals a key biological mechanism that may help plants survive in boron-poor soils, providing valuable insights for developing more resilient crops that can thrive in challenging agricultural environments.

Boron (B) is a crucial micronutrient, particularly in volcanic soils where its deficiency hampers agriculture. Here, we investigate the genetic basis of leaf B accumulation in natural populations of Arabidopsis thaliana that colonized volcanic islands in Cape Verde. Using a combination of genome-wide association studies (GWAS) and mapping in a recombinant intercross population, we identified a case of convergent phenotypic evolution in which multiple variants in the two principal B transporter genes, BOR1 and BOR2, increase leaf B accumulation in parallel. These include multiple tandem duplications at BOR1 that arose independently in different populations. Overall, this study reveals a remarkable case of convergent evolution occurring within a relatively short time scale, where different types of de novo mutations at B efflux transporter genes achieve similar phenotypic outcomes. Further, our findings show that integrating recombinant populations with GWAS in natural populations can improve power to overcome allelic heterogeneity.