Plastid Signals Confer Arabidopsis Tolerance to Water Stress

Abstract

Plastid-to-nucleus retrograde signalling coordinates nuclear gene expression with chloroplast function and is essential for the photoautotrophic life-style of plants. The relationship between plastid signalling and water stress response was investigated with genome uncoupled (gun) mutants, gun1, gun3, and gun5, and an abscisic acid (ABA)-responsible transcription factor mutant, abi4. The results showed that gun1, gun3, gun5, and abi4 mutants suffered from more oxidative damages than the wild-type plants under the water stress and the water stress + herbicide (norflurazon, NF) co-treatment. Superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) activities could not be prompted in the plastidsignalling defective mutants under the stress conditions. At the same time, Lhcb expression was not repressed in the plastid-signalling defective mutants by the NF treatment or water stress. Therefore, the photosynthetic apparatus in the mutant cells could not be closed during the stresses and the excessive light caused more photodamages on the mutant leaves. The roles of GUN1, GUN3, GUN5 and ABI4 proteins in environmental stress adaptation have been discussed.