A cytokinin in soluble RNA from a higher plant

Abstract

Extracts of higher plant tissues are known to contain a number of cytokinins; three have been isolated and definite information obtained regarding their structures. The first, termed zeatin, has been identified as 6-(4-hydroxy-3-methylbut- trans -2-enyl)aminopurine (1, 2), the second is probably 9-β-D-ribofuranosylzeatin (3) and the third has been tentatively identified as 9-β-D-ribofuranosylzeatin-5′-phosphate (4). Very recently a cytokinin, 6-(3-methylbut-2-enyl) aminopurine, has been isolated from liquid cultures of Corynebacterium fascians (5). This compound also occurs as a base in serine transfer RNA derived from yeast (6). Bellamy (7) recently observed that hydrolysates of sheep- and rat-liver RNA possessed appreciable cytokinin activity. RNAs isolated from subcellular particles of rat liver were also hydrolysed and tested for cytokinin activity (7). Nuclear, mitochondrial and ribosomal RNA hydrolysates possessed moderate activity, but RNA from the cytoplasmic fraction (principally soluble RNA) yielded considerably more active hydrolysates (7). Bellamy failed to detect cytokinin activity in hydrolysates of RNA prepared from tobacco cells (7). In the present communication, the detection of a cytokinin in hydrolysates of a higher- plant soluble RNA (s-RNA) is reported for the first time. The factor has been characterized chromatographically.