Inhibition of cell proliferation, cell expansion and differentiation by the Arabidopsis SUPERMAN gene in transgenic tobacco plants

Plant development depends upon the control of growth, organization and diff erentiation of cells derived from shoot and root meristems. Among the genes involved in flower organ determination, the cadastral gene SUPERMAN contro ls the boundary between whorls 3 and 4 and the growth of the adaxial outer ovule integument by down-regulating cell divisions. To determine the precis e function of this gene we overexpressed ectopically the Arabidopsis thalia na (L.) Heynh. SUPERMAN gene in tobacco (Nicotiana tabacum L.). The transge nic plants exhibited a dwarf phenotype. Histologically and cytologically de tailed analyses showed that dwarfism is correlated with a reduction in cell number, which is in agreement with the SUPERMAN function in Arabidopsis. F urthermore, a reduction in cell expansion and an impairment of cell differe ntiation were observed in tobacco organs. These traits were observed in dif ferentiated vegetative and floral organs but not in meristem structures. A potential effect of the SUPERMAN transcription factor in the control of gib berellin biosynthesis is discussed.