Abstract:
Although the roles of hydrogen peroxide (H2O2) and nitric oxide (NO) in elevated CO2-induced stomatal closure have been well known, the enzymatic sources and the relationship between H2O2 and NO during elevated CO2-induced stomatal closure are not fully clear. In the present study, Arabidopsis (Arabidopsis thaliana) wild type, NADPH oxidase and nitrate reductase (NR) mutants were used as materials, the enzymatic routes and the relationship between H2O2 and NO in elevated CO2-led stomatal closure were investigated by means of stomatal bioassay and laser scanning confocal microscopy. Elevated CO2 closed the stomata in wild type, this effect was partially abolished in AtrbohF mutant, and fully abolished in AtrbohD/F. However, like in wild type, elevated CO2 closed the stomata in AtrbohD. The results show that H2O2 sourced from both AtrbohD and AtrbohF is involved in elevated CO2-caused stomatal closure. Furthermore, elevated CO2 promoted NO synthesis in guard cells and stomatal closure in wild type, these effects were completely prevented in Nia1-2 and Nia2-5/Nia1-2, but were not in Nia2-1. The data indicate that Nia1-dependent NO synthesis mediates elevated CO2-triggered stomatal closure. In addition, elevated CO2 induced NO synthesis in guard cells in wild type was fully abolished in AtrbohF and AtrbohD/F, but as in guard cells in wild type, elevated CO2 stimulated H2O2 production in Nia1-2 and Nia2-5/Nia1-2. SNP significantly rescued the defects in AtrbohF and AtrbohD/AtrbohF mutants, but H2O2 did not restore the deficiencies of Nia1-2 and Nia2-5/Nia1-2, in elevated CO2 -induced stomatal closure. These data clearly show that H2O2 induces NO synthesis in elevated CO2-led stomatal closure.
