Mining the natural genetic variation in Arabidopsis thaliana for adaptation to sequential abiotic and biotic stresses

Silvia Coolen,Corné M J Pieterse,Saskia C M Van Wees,Johan A Van Pelt

doi:10.1007/s00425-018-3065-9

Abstract

Main conclusionIn this genome-wide association study, we obtained novel insights into the genetic basis of the effect of herbivory or drought stress on the level of resistance against the fungus Botrytis cinerea.In nature, plants function in complex environments where they encounter different biotic and abiotic stresses individually, sequentially or simultaneously. The adaptive response to a single stress does not always reflect how plants respond to such a stress in combination with other stresses. To identify genetic factors that contribute to the plant’s ability to swiftly adapt to different stresses, we investigated the response of Arabidopsis thaliana to infection by the necrotrophic fungus B. cinerea when preceded by Pieris rapae herbivory or drought stress. Using 346 natural A. thaliana accessions, we found natural genetic variation in the level of resistance against single B. cinerea infection. When preceded by herbivory or drought stress, the level of B. cinerea resistance was differentially influenced in the 346 accessions. To study the genetic factors contributing to the differential adaptation of A. thaliana to B. cinerea infection under multi-stress conditions, we performed a genome-wide association study supported by quantitative trait loci mapping and fine mapping with full genome sequences of 164 accessions. This yielded several genes previously associated with defense to B. cinerea and additional candidate genes with putative roles in the plant’s adaptive response to a combination of herbivory, drought and B. cinerea infection.

Highlights

Under natural conditions, plants encounter many different stresses individually, sequentially or simultaneously
By comparing leaf areas from normally watered and drought-stressed plants, it is clear that the 346 tested A. thaliana accessions respond differently to water withhold, leading to phenotypic variations that range from highly drought sensitive to highly drought tolerant
Because the linkage disequilibrium (LD) of the natural population of A. thaliana accessions used for genome-wide association (GWA) mapping is estimated to be 10–50 kb (Nordborg et al 2005; Kim et al 2007), we considered all genes within 25 kb up- and downstream of each identified single-nucleotide polymorphisms (SNPs) to be candidates for the observed SNP-trait associations

Summary

Introduction

Plants encounter many different stresses individually, sequentially or simultaneously. To withstand these stresses, plants make use of constitutive and induced defenses to ensure survival. Depending on the type of stress, plants activate different hormone-regulated responses, in which JA and ABA signaling is typically engaged upon herbivory or wounding, JA and ET signaling upon infection by necrotrophic pathogens, and SA signaling after infection by biotrophic pathogens. Cross-talk between these hormone signaling pathways is thought to play an important role in the ability of plants to swiftly adjust to a variety of biotic and abiotic environmental conditions, and has, been the focus of many studies on plant stress adaptation To study the genetics of these responses, genome-wide association (GWA) mapping has been used in many studies, revealing genes with important functions in diverse processes of plant growth and survival, whether or not under stress conditions (Atwell et al 2010; Baxter et al 2010; Thoen et al 2017; Proietti et al 2018)

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