A conserved function for arabidopsis SUPERMAN in regulating floral-whorl cell proliferation in rice,a monocotyledonous plant

摘要

Studies of floral organ development in two dicotyledonous plants,Arabidopsis thaliana and Antirrhinum majus,have shown that three sets of genes (A,B and C) can pattern sepals,petals,stamens and carpels [1,2].Mechanisms that define boundaries betweenthese floral whorls are unclear,however,The Arabidopsis gene SUPERMAN (SUP),which encodes a putative ranscription factor,maintains the boundary between stamens and carpels [3-5],possibly by regulating cell proliferation.By ov erexpressing SUP cDNA in rice,we examines whether its effects on whorl boundaries are conserved in a divergent monocotyledonous species.High-level ectopic SUP expression in transgenic rice resulted in juvenile death or dwarf plants with decreased axillary growth.Plants with lowerlevels of SUP RNA were vegetatively normal,but the flowers showed ubiquitous ventral carpel expansion.This was often coupled with reduced stamen number,or occurrence of third-whorl stamen-carpel mosaic organs.Additionally,proliferation of second-whorl ventral cells produced adventitious lodicules,and flowers lost the asymmetry that is normally inherent to this whorl.We predict that SUP is a conserved regulator of floral whorl boundaries and that it affects cell proliferation.