Distribution of phytochrome and chlorophyll-a/b-binding-protein mRNAs in etiolated Avena seedlings.

In 4-d-old dark-grown oat (Avena sativa L.) seedlings, the majority of the type-I-phytochrome (phyA) mRNA was found within 10 mm of the tip of the coleoptile sheath and in the mesocotyl node; almost none was detected in the enclosed primary leaf. In contrast, chlorophyll-a/b-binding-protein (cab) mRNAs were found almost exclusively in the enclosed primary leaf and were barely detectable in total-RNA samples from the coleoptile sheath or mesocotyl node of red-light-treated etiolated seedlings. Separated, dark-grown primary leaves responded to a red-light treatment by increasing cab-mRNA abundance in the absence of the coleoptile sheath or mesocotyl node tissues.