Natural variation in stomata size contributes to the local adaptation of water-use efficiency in Arabidopsis thaliana.

Abstract

Stomata control gas exchanges between the plant and the atmosphere. How natural variation in stomata size and density contributes to resolve trade-offs between carbon uptake and water loss in response to local climatic variation is not yet understood. We developed an automated confocal microscopy approach to characterize natural genetic variation in stomatal patterning in 330 fully sequenced Arabidopsis thaliana accessions collected throughout the European range of the species. We compared this to variation in water-use efficiency, measured as carbon isotope discrimination (δ 13 C). We detect substantial genetic variation for stomata size and density segregating within Arabidopsis thaliana. A positive correlation between stomata size and δ 13 C further suggests that this variation has consequences on water-use efficiency. Genome wide association analyses indicate a complex genetic architecture underlying not only variation in stomatal patterning but also to its covariation with carbon uptake parameters. Yet, we report two novel QTL affecting δ 13 C independently of stomatal patterning. This suggests that, in A. thaliana, both morphological and physiological variants contribute to genetic variance in water-use efficiency. Patterns of regional differentiation and covariation with climatic parameters indicate that natural selection has contributed to shape some of this variation, especially in Southern Sweden, where water availability is more limited in spring relative to summer. These conditions are expected to favour the evolution of drought avoidance mechanisms over drought escape strategies.

Plant phenotyping relevance

自動化共焦点顕微鏡による気孔サイズ・密度の表現型取得法を開発し、330系統へ大規模適用しているため、植物表現型計測が中心である。

Code and data availability

The paper's Data Accessibility statement explicitly deposits raw confocal image data, image analysis scripts, and phenotypic data in a Dryad repository, uploads genotypic phenotype means to AraPheno, and provides authors' GWAS and MTMM analysis scripts on GitHub. All are paper-specific, public, and actionable.