Figure 1.

The onac054 Knockout Mutants Show a Delayed Senescence Phenotype during Dark-Induced Senescence.

(A) Gene structure of ONAC054 and T-DNA insertion sites of two independent knockout lines of ONAC054.

(B) Knockout of ONAC054 in the onac054-1 and onac054-2 mutants was confirmed by RT-PCR analysis. UBQ5 was used as an internal control. WT, wild type.

(C) Plants at different DDI. The wild-type (WT) and onac054-1 mutants grown for 1 month under LD (14 h light per day) conditions were transferred to darkness at 28°C for 12 d.

(D) to (H) The changes in leaf color (D), total Chl level (E), photosystem protein levels (F), ion leakage rate (G), and chloroplast structure (H) in the leaf discs of 1-month-old wild type (WT) and onac054 mutants during dark incubation. Detached leaf discs were incubated on 3 mM MES (pH 5.8) buffer with the abaxial side up at 28°C in darkness and sampled at the specified DDI for each experiment. (F) Antibodies against PSI antenna (Lhca1 and Lhca2), PSII antenna (Lhcb2 and Lhcb4), PSI core (PsaA), and PSII core (CP43) proteins were used for immunoblot analysis. RbcL was detected by Coomassie Brilliant Blue staining.

(E) and (G) The mean and SD were obtained from more than five biological samples (one leaf disc each). Asterisks indicate a significant difference compared to the WT (Student’s t test, **P < 0.01).

(G) G, Grana thylakoid; PG, plastoglobule. Scale bars, 1 μm. These experiments were repeated twice with similar results.