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The survival and growth performance of terrestrial plants, whether in favorable or unfavorable environments, depend essentially on efficient water absorption and management. Most plant species seek water in the soil through continuous growth and development of their roots into a branched architecture. The intrinsic water transport properties of the root tissues (i.e. their hydraulic conductivity) are also important for efficient absorption and water transfer to the rest of the plant.

XND1 transcription factor and water stress tolerance

In this article recently published in Nature Communications, the authors used a genome-wide association analysis to identify genes controlling root hydraulics in Arabidopsis thaliana. They identified the XND1 transcription factor (for "XYLEM NAC DOMAIN 1") as a negative regulator of water transport in A. thaliana roots.

In brief, the authors studied the natural variation of water root transport in 143 accessions of A. thaliana and showed that the diversity of the XND1 genetic background was affecting this trait.

Phenotyping of xnd1 mutants and natural XND1 variants further showed that XND1 modulates root hydraulic conductivity through action on xylem formation and potential indirect effects on aquaporin function and that it diminishes drought stress tolerance.

XND1 may contribute to the trade-off between abiotic stress tolerance and biotic defense

The researchers also made a more unexpected observation: by inhibiting xylem tissue formation, XND1 limits plant infection by the root pathogen Ralstonia solanacearum and the development of the bacterial wilt disease. This study emphasizes a general role of the differentiation of xylem vessels in the response of plants to environmental stresses, whether abiotic (water stress) or biotic (pathogenic bacterium R. solanacearum). More specifically, the functionality of XND1, which is variable among accessions, contributes to resolving a major trade-off in the plant response to these different constraints.