The regulation of RNA synthesis in fern gametophytes by light

Abstract

Morphogenesis and metabolism of the gametophytes (= sporelings) of the common male fern Dryopteris filix-mas are controlled by visible radiation. Short wavelengths visible radiation (= blue light) leads to an increase in protein synthesis and makes possible the formation of "normal" two-dimensional prothallia. Under long wavelengths visible radiation (= red light) the sporelings grow as cellular filaments the protein contents of which are markedly lower than under blue irradiation even under conditions of equal rate of dry matter accumulation in red and blue (OHLENROTH and MOHR, 1963). - It is shown in the present paper that the RNA content of sporelings of the same age is always higher in blue light than in red light (Figs. 1, 3). The blue-dependent increase of RNA occurs faster than the blue-dependent increase of protein (Fig. 2). Furthermore the increase of protein per sporeling is much larger than the increase of RNA (Fig. 4). These facts are in agreement with the hypothesis that in some way or another blue light initiates differential gene activation.The blue light-dependent morphological changes which occur if we put red grown filamentous sporelings under blue light can be measured much faster than the blue light-dependent increase of the bulk protein (Figs. 5, 6). We have to conclude as we did in a previous paper (KASEMIR and MOHR, 1965) that the blue light-dependent increase in the protein content of the sporelings might be mainly due to an increase of chloroplast protein. - The blue light-dependent increase of the RNA content occurs at least as fast as the morphological changes (Figs. 5, 6). This finding is supplemented by the observation (Fig. 8) that blue light markedly and rapidly stimulates the incorporation of (14)C into RNA. The (14)C was applied as (14)C-uridine (U). - It seems that blue light causes an increase of protein synthesis in the chloroplasts as well as in the cytoplasm. Blue light-dependent RNA synthesis seems to be involved in this response. These data support the view that blue light might exert its morphogenetic control through differential gene activation.

The Relationship between the Kinetics of Ribonucleic Acid Accumulation and the Morphological Development of the Fern Gametophyte, Dryopteris borreri

“…Similarly, the percentage of chloroplast RNA did not increase in association with transition in blue-grown gametophytes (Table I). In D. borreri there is, therefore, no evidence for the stimulation of chloroplast RNA synthesis in blue light, as suggested for D. filix-mas (8).…”

“…In D. filix-mas accumulation of the total RNA ceased after 100 hr in red light but continued, although at a reduced rate, in blue light, which resulted in a higher RNA content in the blue-grown tissue (8). Since this was not the case with D. borreri, when accumulation was similar under both red and blue light, reaching a maximum value after 100 hr, a higher RNA content cannot be mandatory for the morphological development of the biplanar gametophyte.…”

“…The RNA content per gametophyte was lower under red than under blue light (8,23) and this difference was attributed to differing amounts of chloroplast RNA (8), since the chloroplasts of Dryopteris filix-mas were larger under blue than under red light (2). The distribution of RNA in various subcellular fractions was examined in Pteridiwn aquilinum grown under red and blue light, and higher RNA contents were observed under blue light for the chloroplast-rich fraction, and also for the nuclei-rich, the mitochondria-rich, and the supernatant fractions (23,24).…”

Réflexions sur les problèmes de rajeunissement chez les végétaux

“…Toujours sur ce matériel, des études concernant le métabolisme protéique et l'évolution quantitiative de l'ARN (Hotta et Osawa, 1958;Hotta, Osawa et Sakaki, 1959 ;Drumm et Mohr, 1967) tendent à conclure à l'existence d'une relation causale spécifique entre la synthèse de protéines et le passage à un mode de croissance bidimensionnelle ; cette interprétation est toutefois mise en doute par Miller (1968).…”

The Transition From Filamentous to Two‐dimensional Growth in Fern Gametophytes. Iv. Initial Events

“…The first event to be observed was an expansion in the apical region of the filament (Drumm and Mohr, 1967;Dill and Branton, 1968;Davis, 1969). These changes have been studied in detail in only a few instances.…”