Natural variation at XND1 impacts root hydraulics and trade-off for stress responses in Arabidopsis

Ning Tang,Fabienne Vailleau,Olivier Loudet,Fabien Lonjon,Christophe Maurel,Zaigham Shahzad

doi:10.1038/s41467-018-06430-8

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.

Highlights

Soil water uptake by roots is a key component of plant performance and adaptation to adverse environments
Conditional genome wide association (GWA) mapping using 250k single nucleotide polymorphisms (SNP) data[20], and an accelerated mixed-model algorithm method with four markers as cofactors[21] revealed two SNPs that were significantly associated with Lpr variation (Bonferroni multiple testing correction at α = 0.05) and contributed to 18.3% and 7.3% of the genetic variance, respectively (Fig. 1a)
None of these genes showed SNPs that were in strong linkage disequilibrium (LD) with the corresponding GWA studies (GWAS) peak SNP (Supplementary Figure 2)

Summary

Introduction

Soil water uptake by roots is a key component of plant performance and adaptation to adverse environments. Drought impacts xylem differentiation further supporting a crucial role of vascular transport in these conditions[5,8] This view may not apply to certain species or under mild water stress since intraspecific variation of xylem size in major crops such as rice was not associated to any growth advantage, especially under water deficit[11]. Detailed studies have revealed how positioning of xylem axes contributes to early vascular pattern formation and how subsequent differentiation of xylem tracheary elements occurs through cell clearance by programmed cell death and deposition of lignin in secondary cell walls[12] These developmental processes are controlled by regulatory networks involving NAC (NAM, ATAF1,2, and CUC2)[13] and MYB (myeloblastosis)-type transcription factors[14]. Our study reveals how genetic variation at XND1 may contribute to the trade-off between abiotic stress tolerance and biotic defense in Arabidopsis

Methods

Results

Conclusion