Cross species multi-omics reveals cell wall sequestration and elevated global transcript abundance as mechanisms of boron tolerance in plants.

Abstract

Boron toxicity is a worldwide problem for crops, yet we have a limited understanding of the genetic responses and adaptive mechanisms to this stress in plants. We employed a cross-species comparison between boron stress-sensitive Arabidopsis thaliana and its boron stress-tolerant extremophyte relative Schrenkiella parvula and a multi-omics approach integrating genomics, transcriptomics, metabolomics, and ionomics to assess plant responses and adaptations to boron stress. S. parvula maintains a lower level of total boron and free boric acid than A. thaliana when grown with excess boron. S. parvula excludes excess boron more efficiently than A. thaliana, which we propose is partly driven by SpBOR5, a boron transporter that we functionally characterized in the current study. Both species use cell walls as a partial sink for excess boron. When accumulated in the cytoplasm, excess boron appears to interrupt RNA metabolism. The extremophyte facilitates critical cellular processes while maintaining the pool of ribose-containing compounds that can bind with boric acid. The S. parvula transcriptome is pre-adapted to boron toxicity. It exhibits substantial overlaps with the A. thaliana boron-stress responsive transcriptome. Cell wall sequestration and increases in global transcript levels under excess boron conditions emerge as key mechanisms for sustaining plant growth under boron toxicity.