Early Morphogenetic Changes During Phytochrome-induced Fern Spore Germination II. Transcriptional and Translational Events

Abstract

During early germination of unicellular spores, separation between molecular processes induced by hydration or by photoinduction was possible. There was an extensive adenosine incorporation into low molecular mass, poly(A) rich RNA composed of 30 to 60 nucleotides during the pre-photoinduction phase immediately after hydration. It was followed by gradual increase in the rate of cytoplasmic rRNA synthesis. Photoinduction by 2 short red irradiations given shortly after the preinduction phase caused an immediate 2 fold increase in the rate of ³H-adenosine incorporation into this low molecular mass RNA followed by a heavy shift to the production of rRNAs starting 10h after photoinduction. An increase in mRNA template activity was observed in a cell free translation system 16h after photoinduction: A 30,000d protein and 48,000d protein were preferentially synthesized. Still, the rate and pattern of ³⁵S-methionine incorporation in vivo remained unchanged during the first two days after photoinduction. Then methionine incorporation rapidly rose to four times the rate of the blue light (non photoinduced) control. The delay of over a day between the photoinduced appearance of new mRNAs and in vivo increase of protein synthesis suggests that.there are separate transcriptional and translational controls during Pteris spore germination.