Cytokinins and Differentiation Processes in Mercurialis annua: Genetic Regulation, Relations with Auxins, Indoleacetic Acid Oxidases, and Sexual Expression Patterns

Cytokinins in apices of eight isogenic lines of Mercurialis annua were compared (high performance liquid chromatography-gas chromatography mass spectroscopy-computer system). These apices develop normal staminate or pistillate differentiation processes (sex series lines) or empty (sterile), semiempty (semisterile), and full anthers (restored fertile male) in the sterility series in which a pistillate line was constructed. Both series developed two different cytokinin pathways: trans-cytokinins characterized the sex series, whereas the cis pathway characterized the sterility series. Drastic changes in the trans pathway (0/250 nanograms trans-zeatin and 166/0 nanograms zeatin nucleotide) induced staminate/pistillate differentiations. Less drastic quantitative changes in the cis pathway induced sterility or restored fertility compared to normal fertile anthers (192 or 669 nanograms/traces). The action of the complete cis-pathway was morphologically effective in the sterility series when the ratio of cis to trans pathways was 1:2 or 1:1 instead of 1:3. A final diagram shows the action of each sex or sterility allele on the enzymes controlling specific metabolites in both pathways. The discussion provides insights on the regulation of cytokinin-auxin balances specific for each kind of reproductive differentiation.