Relationships Between the Content of Basic Nuclear Proteins, Chromatin Structure, rDNA Transcription and Cell Size in Different Tissues7

Abstract

Fast Green stainability of basic nuclear proteins, nuclear chromatin structure, intensity of rDNA transcription and cell size were investigated in different tissues of the maize root apex. Average cell size of the various tissues was found to be correlated not only with the respective nuclear DNA content, but also with the nuclear chromatin structure. Moreover, close relationships were observed between nuclear chromatin structure, content of Fast Green-stainable basic nuclear proteins and the intensity of rDNA transcription. Our results suggest a direct relationship between a decreased Fast Green stainability of basic (perhaps lysine-rich)nuclear proteins and a lower density of nuclear chromatin structure. This, in turn, seems to enable a more efficient utilization of information encoded in DNA templates. Ribosomal RNA transcripts initiation and elongation appear to be especially relevant in determining cell size. Intensity of these first steps of rRNA synthesis exhibits, in contrast to rRNA transcript maturation, a tissue-specific pattern and depends on a loose chromatin structure.