Genetic controls of short- and long-term stomatal CO(2) responses in Arabidopsis thaliana

BACKGROUND AND AIMS: The stomatal conductance (g(s)) of most plant species decreases in response to elevated atmospheric CO(2) concentration. This response could have a significant impact on plant water use in a future climate. However, the regulation of the CO(2)-induced stomatal closure response is not fully understood. Moreover, the potential genetic links between short-term (within minutes to hours) and long-term (within weeks to months) responses of g(s) to increased atmospheric CO(2) have not been explored. METHODS: We used Arabidopsis thaliana recombinant inbred lines originating from accessions Col-0 (strong CO(2) response) and C24 (weak CO(2) response) to study short- and long-term controls of g(s). Quantitative trait locus (QTL) mapping was used to identify loci controlling short- and long-term g(s) responses to elevated CO(2), as well as other stomata-related traits. KEY RESULTS: Short- and long-term stomatal responses to elevated CO(2) were significantly correlated. Both short- and long-term responses were associated with a QTL at the end of chromosome 2. The location of this QTL was confirmed using near-isogenic lines and it was fine-mapped to a 410-kb region. The QTL did not correspond to any known gene involved in stomatal closure and had no effect on the responsiveness to abscisic acid. Additionally, we identified numerous other loci associated with stomatal regulation. CONCLUSIONS: We identified and confirmed the effect of a strong QTL corresponding to a yet unknown regulator of stomatal closure in response to elevated CO(2) concentration. The correlation between short- and long-term stomatal CO(2) responses and the genetic link between these traits highlight the importance of understanding guard cell CO(2) signalling to predict and manipulate plant water use in a world with increasing atmospheric CO(2) concentration. This study demonstrates the power of using natural variation to unravel the genetic regulation of complex traits.