Abstract
Nuclear DNA and AgNOR-area quantity have been measured cytophotometrically, the number of silver grains after in situ3 H rDNA/DNA hybridization has been counted, and the level of rDNA methylation has been estimated in root meristems, differentiated root zones, hypocotyls, cotyledons, and leaves of 7-day-old seedlings of Lupinus luteus. DNA content increases by endoreplication, reaching the average DNA C-value of 4.2, in the meristem, 6.6C in hypocotyl, 15.9C in cotyledon, and 3.3C in leaf. The quantity of AgNOR-area, the highest in root meristem, does not follow DNA C-value. Number of grains after in situ 3 H rDNA/DNA hybridization corresponds to DNA amount, but their distribution differs, showing in many cases perinucleolar localization in organs displaying low AgNOR-area quantity. Southern hybridization has not demonstrated detectable changes in level rDNA methylation. We suggest that the low level of rDNA expression in non-meristematic tissues coul d be related to rDNA inactivation caused by its translocation into nucleolus-associated heterochromatin.
Published Version
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