# Arabidopsis thaliana exhibits wide within‐species variation in tolerance to boron limitation and root and shoot trait resilience associate with a pleiotropic locus

## TL;DR

This study finds that some Arabidopsis plants can tolerate low boron levels better due to specific root traits and a genetic region linked to resilience.

## Contribution

The study identifies a genetic locus and root traits associated with boron efficiency in Arabidopsis.

## Key findings

- Seven Arabidopsis accessions showed high tolerance to boron deficiency with minimal biomass reduction.
- Boron-efficient plants maintained lateral root growth under B limitation.
- A QTL on chromosome 4 is linked to root and shoot resilience to B limitation.

## Abstract

To improve plant tolerance to suboptimal availability of the micronutrient boron (B), it is crucial to understand the mechanisms plants have evolved to tolerate B‐limited conditions.We assessed temporal physiological, ionomic and molecular responses to B deficiency across 185 Arabidopsis thaliana accessions grown in soil‐substrate in an automated phenotyping system and on agar plates.Whilst profound shoot‐ and root‐growth inhibition was observed in most accessions under B limitation, seven highly B‐deficiency tolerant accessions with < 20% reduced fresh and digital biomass accumulation were identified. Boron‐efficient accessions were characterised by sustaining lateral more than primary root growth under B limitation. Whilst expression of B transporters increased under B limitation, no correlations between expression and B uptake or B efficiency were observed, suggesting increased B‐use efficiency in B‐efficient accessions. Phylogenetic analysis suggests B efficiency evolved independently multiple times in response to local environmental needs. Genome‐wide association analyses identified a QTL on chromosome 4 that is associated with both root and shoot resilience to B limitation.Our results suggest that an optimised root system contributes to maintaining shoot productivity in B‐limited conditions. Further dissection of the identified QTL and candidate genes will form an important strategy for elucidating the molecular control of B efficiency.

To improve plant tolerance to suboptimal availability of the micronutrient boron (B), it is crucial to understand the mechanisms plants have evolved to tolerate B‐limited conditions.

We assessed temporal physiological, ionomic and molecular responses to B deficiency across 185 Arabidopsis thaliana accessions grown in soil‐substrate in an automated phenotyping system and on agar plates.

Whilst profound shoot‐ and root‐growth inhibition was observed in most accessions under B limitation, seven highly B‐deficiency tolerant accessions with < 20% reduced fresh and digital biomass accumulation were identified. Boron‐efficient accessions were characterised by sustaining lateral more than primary root growth under B limitation. Whilst expression of B transporters increased under B limitation, no correlations between expression and B uptake or B efficiency were observed, suggesting increased B‐use efficiency in B‐efficient accessions. Phylogenetic analysis suggests B efficiency evolved independently multiple times in response to local environmental needs. Genome‐wide association analyses identified a QTL on chromosome 4 that is associated with both root and shoot resilience to B limitation.

Our results suggest that an optimised root system contributes to maintaining shoot productivity in B‐limited conditions. Further dissection of the identified QTL and candidate genes will form an important strategy for elucidating the molecular control of B efficiency.