Tang N, Shahzad Z, Lonjon F, Loudet O, Vailleau F, Maurel C✉ (2018) Natural variation at XND1 impacts root hydraulics and trade-off for stress responses in Arabidopsis. Nat. Commun., 9:3884

This work shows that, by inhiting the differentiation of xylem vessels in root tips, the XND1 transcription factor acts on the water transport capacity of roots and thereby on plant tolerance to drought. Through its effects on xylem, XND1 also interferes with the progression of pathogenic bacteria throughout the plant. Finally, this work uncovers the significance of natural variation at XND1. The activity of the gene, which varies among natural isolates, contributes to major trade-off between resistance to abiotic (drought) and biotic (bacterial infection) stresses in Arabidopsis.

Abstract : Soil water uptake by roots is a key component of plant performance and adaptation to adverse environments. Here, we use a genome-wide association analysis to identify the XYLEM NAC DOMAIN 1 (XND1) transcription factor as a negative regulator of Arabidopsis root hydraulic conductivity (Lpr). The distinct functionalities of a series of natural XND1 variants and a single nucleotide polymorphism that determines XND1 translation efficiency demonstrate the significance of XND1 natural variation at species-wide level. Phenotyping of xnd1 mutants and natural XND1 variants show that XND1 modulates Lpr through action on xylem formation and potential indirect effects on aquaporin function and that it diminishes drought stress tolerance. XND1 also mediates the inhibition of xylem formation by the bacterial elicitor flagellin and counteracts plant infection by the root pathogen Ralstonia solanacearum. Thus, genetic variation at XND1, and xylem differentiation contribute to resolving the major trade-off between abiotic and biotic stress resistance in Arabidopsis.