Light regulation of specific mRNA species in Lemna gibba L. G-3

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Abstract
Polyadenylated RNA was isolated from L. gibba L. G-3 and translated in a cell-free system from wheat germ. When plants were placed into complete darkness for 4 days, then returned to light for 18 h, increased amounts of polyadenylated mRNA for at least 2 polypeptides were detected by in vitro translation over those amounts present in the dark. These 2 polypeptides have MW of 32,000 and 20,000. The 20,000 dalton polypeptide was identified by immunoprecipitation as the precursor to the small subunit of the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39]. The polyadenylated mRNA that codes for the small subunit is not detectable by immunoprecipitation of translation products in the dark-treated tissue. Plants growing in the light actively synthesize both subunits of ribulose-1,5-bisphosphate carboxylase, but synthesis of these proteins was greatly diminished in plants placed in darkness for 4 days. Apparently white light can dramatically affect the steady-state levels of specific polyadenylated mRNA.