2,4-Dichlorophenoxyacetic Acid-enhanced Phosphorylation of Soybean Nuclear Proteins

Abstract

In vitro nuclear protein phosphorylation is enhanced i nuclei isolated from 2,4-dkcorophenoxyacetic acid (2,4-D)-treated mature soybean (Glycine mar) hypocotyl reltive to nuclei from untreated tise. Evidence derived in numerous systems is compatible with the hypothesis that at least some chromosomal proteins participate in transcriptional regulation. Changes in the types and quantities and various modifications of these proteins (e.g. methylation, acetylation, phosphorylation, and thiolation) occur during passage through the cell cycle and during periods of increased template transcription (for reviews, see refs. 14 and 21). Histones were first shown to restrict template activity in 1962 (9). In view of their general lack of species and tissue specificity, histones are now thought to play primarily structural roles (21), thereby resulting in general template restriction. In contrast, nonhistone proteins by virtue of their heterogeneity and tissue and species specificity may participate more specifically in gene regulation (14,21 (27).Application of the synthetic auxin, 2,4-D, to etiolated soybean seedlings causes very large increases in RNA synthesis in the mature region of the hypocotyl (13). Ribosomal RNA is preferentially synthesized in response to 2,4-D treatment (10, 13), and this increase is associated with a 5-to 8-fold increase in RNA polymerase I activity (8). While auxin does increase the synthesis of all species of RNA including short lived mRNA and heterodisperse nuclear RNA (13), RNA polymerase II activity is enhanced less than 30% if at all (8). While increased RNA polymerase I activity may account for the increase in rRNA synthesis, changes in the level of RNA polymerase II alone do not seem sufficient to explain the increased synthesis of heterodisperse nuclear RNA and mRNA. Alteration of chromatin template availability is one mechanism by which 2,4-D could affect the synthesis of informational RNA without requiring increased RNA polymerase II activity. Such a model would be consistent with results indicating that chromatin isolated from IAA-treated lentil roots is more available for in vitro transcription by RNA

Isolation and Characterization of a Chromatin-associated Protein Kinase from Soybean

“…Detailed studies on soybean chromatin protein phosphorylation indicate that increases in chromatin protein phosphorylation and chromatin-associated casein kinase activity are correlated with auxin-enhanced RNA synthesis (21). Data in other systems suggest that chromatin protein phosphorylation may alter chromatin template availability for transcription (10, 13; refs.…”

“…Concomitant with auxin-enhanced RNA synthesis in soybean hypocotyls (11) there is an increase in nuclear protein phosphorylation and in nuclear casein kinase activity (21). Moreover, RNA polymerase preparations from soybean were found to copurify with a protein kinase activity during the early stages of purification (unpublished).…”

Immunological Properties of Rat Lens Gamma-Crystallins

“…Preparation of lenses, extraction of water-soluble proteins, protein separation by pre parative flat bed isoelectric focusing and immunization procedures of rabbits to raise specific antisera have been described in an accompanying paper [Vornhagen et al, 1982]. Immunodiffusion was performed according to Ouchterlony and Nilsson [1978], fused rocket immunoelectrophoresis according to Laurell [1965] and SDS-polyacrylamide (10%) gel electrophoresis according to Murray and Key [1978]. Molecular weight markers were obtained from Sigma and BDH Chemicals.…”

Protein Tyrosine Phosphorylation during Phytohormone-Stimulated Cell Proliferation in Arabidopsis Hypocotyls

“…Phytohormones control many aspects of plant growth and development. Protein phosphorylation was enhanced in nuclei isolated from auxin-treated soybean hypocotyl (Murray and Key 1978). Reddy et al (1987) presented evidence for auxin-regulated changes in protein phosphorylation in pea segments.…”