Quantitative trait loci mapping and transcriptome analysis reveal candidate genes regulating the response to ozone in Arabidopsis thaliana

As multifaceted molecules, reactive oxygen species (ROS) are known to accumulate in response to various stresses. Ozone (O-3) is an air pollutant with detrimental effect on plants and O-3 can also be used as a tool to study the role of ROS in signalling. Genetic variation of O-3 sensitivity in different Arabidopsis accessions highlights the complex genetic architecture of plant responses to ROS. To investigate the genetic basis of O-3 sensitivity, a recombinant inbred line (RIL) population between two Arabidopsis accessions with distinct O-3 sensitivity, C24 (O-3 tolerant) and Te (O-3 sensitive) was used for quantitative trait loci (QTL) mapping. Through analysis of QTL mapping combined with transcriptome changes in response to O-3, we identified three causal QTLs and several potential candidate genes regulating the response to O-3. Based on gene expression data, water loss and stomatal conductance measurement, we found that a combination of relatively low stomatal conductance and constitutive activation of salicylic acid (SA)-mediated defence signalling were responsible for the O-3 tolerance in C24. Application of exogenous SA prior to O-3 exposure can mimic the constitutive SA signalling in C24 and could attenuate O-3-induced leaf damage in the sensitive Arabidopsis accessions Te and Cvi-0. Reactive oxygen species (ROS) are essential signaling molecules in plants that are also involved in the regulation of cell death. Genes that regulate ROS-induced cell death were identified through QTL mapping and transcriptome analysis in ozone treated Arabidopsis accessions C24 and Te. A crucial protective role for the hormone salicylic acid was identified.