Ribonucleic acid synthesis by chromatin isolated from Phaseolus aureus Roxb. : The effect of endogenous ribonuclease

Chromatin was isolated from the hypocotyls of Phaseolus aureus Roxb. and assayed for endogenous RNA polymerase (EC 2.7.7.6) activity in vitro. The molecular size of the RNA product, measured by polyacrylamide gel electrophoresis, was found to be much smaller than that known to be synthesised in vivo and was affected by the assay temperature. Although conventional enzyme assays provided no evidence for the presence of ribonuclease in chromatin, a more sensitive technique revealed sufficient ribonuclease activity to degrade high-molecular weight RNA to smaller fragments. The inclusion of unlabelled exogenous RNA in the media for chromatin preparation and RNA polymerase assay substantially increased the molecular-weight of the RNA products synthesised in vitro.Peer reviewe

Auxin response factors ARF6 and ARF8 promote jasmonic acid production and flower maturation.

Pollination in flowering plants requires that anthers release pollen when the gynoecium is competent to support fertilization. We show that in Arabidopsis thaliana, two paralogous auxin response transcription factors, ARF6 and ARF8, regulate both stamen and gynoecium maturation. arf6 arf8 double-null mutant flowers arrested as infertile closed buds with short petals, short stamen filaments, undehisced anthers that did not release pollen and immature gynoecia. Numerous developmentally regulated genes failed to be induced. ARF6 and ARF8 thus coordinate the transition from immature to mature fertile flowers. Jasmonic acid (JA) measurements and JA feeding experiments showed that decreased jasmonate production caused the block in pollen release, but not the gynoecium arrest. The double mutant had altered auxin responsive gene expression. However, whole flower auxin levels did not change during flower maturation, suggesting that auxin might regulate flower maturation only under specific environmental conditions, or in localized organs or tissues of flowers. arf6 and arf8 single mutants and sesquimutants (homozygous for one mutation and heterozygous for the other) had delayed stamen development and decreased fecundity, indicating that ARF6 and ARF8 gene dosage affects timing of flower maturation quantitatively