Developmental changes in the levels of iRD21 and mRD21 in Arabidopsis leaves during senescence and in seedlings after seed germination. A, Total protein (10 μg) from the first and second rosette leaves of 15-, 20-, 25-, 30-, and 35-d-old Arabidopsis plants was subjected to SDS-PAGE followed by immunoblot analysis with anti-RD21 antibodies (anti-RD21). B, Ten dry seeds and 10 seedlings at 1 to 7 d after germination were homogenized in 200 μL of SDS-PAGE sample buffer. Each extract (10 μL) was subjected to SDS-PAGE and subsequent staining with Coomassie Blue (top, CBB) or immunoblot analysis with anti-RD21 antibodies (bottom, anti-RD21). i, iRD21; m, mRD21; 12S, 12S globulin, a seed storage protein.