Natural variation in ozone sensitivity among Arabidopsis thaliana accessions and its relation to stomatal conductance

Genetic variation between naturally occurring populations provides a unique source to unravel the complex mechanisms of stress tolerance. Here, we have analysed O₃ sensitivity of 93 natural Arabidopsis thaliana accessions together with five O₃-sensitive mutants to acute O₃ exposure. The variation in O₃ sensitivity among the natural accessions was much higher than among the O₃-sensitive mutants and corresponding wild types. A subset of nine accessions with major variation in their O₃ responses was studied in more detail. Among the traits assayed, stomatal conductance (gst) was an important factor determining O₃ sensitivity of the selected accessions. The most O₃-sensitive accession, Cvi-0, had constitutively high gst, leading to high initial O₃ uptake rate and dose received during the first 30 min of exposure. Analyzing O₃-induced changes in stress hormone concentrations indicated that jasmonate (JA) concentration was also positively correlated with leaf damage. Quantitative trait loci (QTL) mapping in a Col-0 x Cvi-0 recombinant inbred line (RIL) population identified three QTLs for O₃ sensitivity, and one for high water loss of Cvi-0. The major O₃ QTL mapped to the same position as the water loss QTL further supporting the role of stomata in regulating O₃ entry and damage.