Fragmentation of DNA and chromatin during senescence in barley leaves.

DNA or chromatin from young (7 day) first seedling leaves of barley showed only one component which migrated little into 1% agarose gels on electrophoresis. However, DNA or chromatin from senescent (17-, 19-, and 23-day-old) leaves showed additional dispersed components migrating throughout the length of the gel which increased with age. These low molecular weight components increased even more on autodigestion of chromatin from senescent leaves by its associated DNase or by digestion of DNA from senescent leaves with partially purified chromatin DNase. DNA or chromatin from young leaves also produced gel pattern similar to old leaves on digestion with partially purified chromatin DNase from old barley leaves. Thus, fragmentation of DNA and chromatin by chromatin associated DNase, previously shown to increase 4000% on aging, occurs during senescence in barley leaves.