Strigolactone and cytokinin act antagonistically in regulating rice mesocotyl elongation in darkness

Strigolactones have been defined as a new group of phytohormones that regulate shoot branching. Tthe phenotypes of strigolacton-related rice (Oryza sativa) dwarf (d) mutants demonstrated that SLs inhibit mesocotyl elongation by controlling cell division. Moreover, the trans-zeatin, one of active cytokinins, content of mesocotyls was increased in the SL-deficient d10-1 and SL-insensitive d14-1 mutants. To examine if there are genes related to cytokinin-biosynthesis or -degradation among the strigolactone-responsive genes expressed in the mesocotyl, we carried out microarray analyses using d10-1, d14-1 and the wild-type grown under dark conditions, with or without pretreatment of a synthetic strigolactone analog, GR24. Gene expression profiles in 4-day-old mesocotyls of dwarf (d) mutants (d10-1 and d14-1) and wild-type germinated under dark conditions with or without treatment of 1 μM GR24 were analyzed. Three biological replicates were prepared for each conditions, and a total of eighteen samples were analyzed.