Abstract
Background and AimsThe stomatal conductance (gs) of most plant species decreases in response to elevated atmospheric CO2 concentration. This response could have a significant impact on plant water use in a future climate. However, the regulation of the CO2-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 gs to increased atmospheric CO2 have not been explored.MethodsWe used Arabidopsis thaliana recombinant inbred lines originating from accessions Col-0 (strong CO2 response) and C24 (weak CO2 response) to study short- and long-term controls of gs. Quantitative trait locus (QTL) mapping was used to identify loci controlling short- and long-term gs responses to elevated CO2, as well as other stomata-related traits.Key ResultsShort- and long-term stomatal responses to elevated CO2 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.ConclusionsWe identified and confirmed the effect of a strong QTL corresponding to a yet unknown regulator of stomatal closure in response to elevated CO2 concentration. The correlation between short- and long-term stomatal CO2 responses and the genetic link between these traits highlight the importance of understanding guard cell CO2 signalling to predict and manipulate plant water use in a world with increasing atmospheric CO2 concentration. This study demonstrates the power of using natural variation to unravel the genetic regulation of complex traits.
Highlights
Stomata are microscopic pores in the epidermis, surrounded by two guard cells that regulate their aperture by changes in turgor pressure
We observed significantly weaker short-term stomatal CO2 response, i.e. the percentage decrease in stomatal conductance following a doubling of the CO2 concentration (Welch’s t-test, P = 0.01, n = 6), as well as lower absolute gs at both 400 and 800 ppm CO2 of C24 compared with Col-0 (Welch’s t-test, P < 0.001 and P = 0.002, respectively, n = 6; Fig. 1B), confirming the results of the pilot study
To investigate the genetic basis for the variation in stomatal regulation between Col-0 and C24, we quantified several stomata-related traits among 100 Recombinant inbred lines (RILs) originating from a reciprocal cross between these accessions and used these data for Quantitative trait locus (QTL) mapping
Summary
Stomata are microscopic pores in the epidermis, surrounded by two guard cells that regulate their aperture by changes in turgor pressure. Almost all gas exchange between plants and the atmosphere occurs through the stomata, the stomatal aperture is regulated to balance the trade-off between CO2 uptake for photosynthesis and transpirational water loss. Elevated CO2 concentration induces partial closure of stomata in most plant species (Morison, 1998; Ruszala et al, 2011; Franks and Britton-Harper, 2016). This reduces transpirational water loss and improves leaf-level water economy. With a projected doubling of the atmospheric CO2 concentration within the 100 years (IPCC, 2013), the stomatal CO2 response could have a significant impact on global plant water use under future climatic conditions. Knowledge about the genetic regulation of stomatal conductance (gs) in response to elevated CO2 could facilitate the improvement of crop water-use efficiency in a future climate
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