Minimal influence of G-protein null mutations on ozone-induced changes in gene expression, foliar injury, gas exchange and peroxidase activity in Arabidopsis thaliana L.

摘要

Ozone (O₃) uptake by plants leads to an increase in reactive oxygen species (ROS) in the intercellular space of leaves and induces signalling processes reported to involve the membrane-bound heterotrimeric G-protein complex. Therefore, potential G-protein-mediated response mechanisms to O₃ were compared between Arabidopsis thaliana L. lines with null mutations in the alpha - and beta -subunits (gpa1-4, agb1-2 and gpa1-4/agb1-2) and Col-0 wild-type plants. Plants were treated with a range of O₃ concentrations (5, 125, 175 and 300 nL L-1) for 1 and 2 d in controlled environment chambers. Transcript levels of GPA1, AGB1 and RGS1 transiently increased in Col-0 exposed to 125 nL L-1 O₃ compared with the 5 nL L-1 control treatment. However, silencing of alpha and beta G-protein genes resulted in little alteration of many processes associated with O₃ injury, including the induction of ROS-signalling genes, increased leaf tissue ion leakage, decreased net photosynthesis and stomatal conductance, and increased peroxidase activity, especially in the leaf apoplast. These results indicated that many responses to O₃ stress at physiological levels were not detectably influenced by alpha and beta G-proteins.