FIGURE 5.

Leaves of pls4 exhibit a severe senescence phenotype under natural conditions. (A) TEM analysis of the flag leaves of the WT and pls4 mutant at the heading stage. GTK, granum thylakoid; PG, plastoglobule. Bars = 2 μm (a,d), 0.5 μm (b,e), 0.2 μm (c,f). (B) Accumulation of O₂^– radicals in naturally senescence leaves, visualized by staining with NBT. (C–F) H₂O₂ and MDA contents, CAT and POD activity in the WT and pls4 mutant at the tillering and heading stages. The data presented are the means ± SDs of three biological replicates. *P < 0.05; **P < 0.01 (Student’s t-test). FW, fresh weight. (G) Changes in transcript levels of Chl degradation-associated genes in the leaves of the WT and pls4 mutant at the tillering stage. The genes are as follows: OsNOL (LOC_Os03g45194) and OsNYC1 (LOC_Os01g12710), two short-chain dehydrogenase/reductases, represent Chl b reductases; OsNYC3, which encodes an α/β hydrolase-fold family protein (LOC_Os06g24730); OsNYC4, which encodes thylakoid formation 1, and is involved with chloroplast precursors (LOC_Os07g37250); OsPAO, which encodes a pheophorbide oxygenase (LOC_Os03g05310); and OsRCCR1, which encodes reductase of Chl-like catabolites (LOC_Os10g25030). (H) Relative expression of a set of genes associated with senescence in the WT and the pls4 mutant. The genes include the following: OsCatB, catalase (LOC_Os06g51150); OsPOD1 (LOC_Os01g22370) and OsPOD2 (LOC_Os03g22010), two peroxidases; OsAPX1 (LOC_Os03g17690) and OsAPX2 (LOC_Os07g49400), two ascorbate peroxidases; and OsH36, aminotransferase, senescence-induced protein (LOC_Os05g39770). The data presented are the means ± SDs of three biological replicates.