Several parameters of meiosis have been studied in cultured anthers of Trillium erectum. The accessibility of labeled substrates to meiotic cells and the fate of these substrates in relation to meiotic stage have been determined. Evidence has been adduced for the synthesis of RNA and protein during the meiotic cycle well after chromosome duplication. The effect of interfering with systems directly or indirectly connected with protein formation has been studied by means of chloramphenicol, 8-azaguanine, 5-methyltryptophan, and ethionine. Administration of these reagents at different intervals in the cycle elicits correspondingly different responses thereby indicating a periodicity in the activities of different systems. The following processes have been shown to be affected in these experiments: chromosome segregation, chromosome morphology, cytokinesis, wall synthesis, and enzyme appearance. The possibility of experimentally altering the normal sequence of events has also been shown.

Azaguanine↗

PubMed1963

SYNTHESIS OF MESSENGER-LIKE RIBONUCLEIC ACID AND PROTEIN DURING MEIOSIS IN ISOLATED CELLS OF TRILLIUM ERECTUM.

The synthesis of RNA and protein by cultures of isolated microsporocytes has been demonstrated. The variation in capacities of such cultures to perform syntheses is a function of meiotic stage and parallels the pattern of changes observed for microsporocytes in situ. A principal feature of this pattern is the induction of syntheses during pachytene and diplotene, stages at which the chromosomes are partly contracted. By use of Actinomycin D, chloramphenicol, pulse-labeling with P(32)-phosphate, and nucleotide analyses of RNA digests, part of the RNA synthesized has been shown to correspond to messenger RNA. Analysis of reaction rates and the overlappings of protein and RNA synthesis indicates that the spread of cytological events in Trillium is not purely a function of the low temperature at which it occurs but, presumably, arises from a complement of regulatory devices which govern the periodic onset of reactions within the cells. The main conclusion drawn from the whole of these studies is that the sequence of morphological changes associated with chromosome contraction and movement during meiosis is accompanied by a set of gene transcriptions. Although comparatively few genes are presumed to be active during meiosis, the action of such genes may be essential to a translation of some of the information embodying the meiotic sequence which has been stored in the genome in the course of evolution.

Cell Division↗

PubMed1961

Transient phosphorylation of deoxyribosides and regulation of deoxyribonucleic acid synthesis.

Microspores isolated from Lilium longiflorum and Trillium erectum were studied with respect to their capacities for phosphorylating deoxyribosides in vitro. It was found that such capacities are manifest only during brief intervals of time adjacent to periods of DNA synthesis, and that none of the neighboring cells in the anther acquire them. The observed patterns of behavior are interpreted in terms of enzyme induction as a device for regulating DNA synthesis.

DNA↗

PubMed1961

Deamination of deoxycytidine and 5-methyldeoxycytidine in developing anthers of Lilium longiflorum (var. Croft).

A study has been made of developmental variations in anthers of Lilium longiflorum with respect to the deamination of deoxycytidine and 5-methyldeoxycytidine. Although a periodicity of enzymatic activities surrounding the mitotic cycle has been found, the over-all evidence is against the significance of such periodicity to chromosome duplication. On the basis of evidence obtained a distinction has been drawn between enzyme systems functioning in a broad supporting role and those immediately tied to morphogenetic events.

Deamination↗

PubMed1959