Figure 4.

Analysis of SA-related responses in pp2a mutant leaves displaying age-dependent yellowing. A, Phenotypic characteristics of 7-week–old, short day-grown wild type, pp2a-b´γ, pp2a-b´γ P35S:PP2A-B′γ, pp2a-b′ζ, pp2a-b′γζ, and the pp2a-b′γ sid2 double mutant. Scale bars = 1 cm. B, Representative immunoblots depicting accumulation of the SA-signaling marker PR1 and the senescence marker SAG12 in the yellowing apical halves of pp2a-b′γ leaves. Leaves of 7-week–old wild type, pp2a-b′γ, pp2a-b′γ P35S:PP2A-B′γ, pp2a-b′ζ, pp2a-b′γζ, cpk1, sid2, and the pp2a-b′γ sid2 double mutant were harvested and split into apical and basal halves. Total extracts were isolated and separated by SDS-gel electrophoresis and subjected to immunoblot analysis with antibodies specific to PR1 or SAG12.