Ectopic expression AINTEGUMENTA in Arabidopsis plants results in increasedgrowth of floral organs

AINTEGUMENTA [ANT] was previously shown to be involved in floral organ init iation and growth in Arabidopsis. ant flowers have fewer and smaller floral organs and possess ovules that lack integuments and a functional embryo sa c. The present work shows that young floral meristems of ant plants are sma ller than those in wild type. Failure to initiate the full number of organ primordia in ant flowers may result from insufficient numbers of meristemat ic cells. The decreased size of ant floral organs appears to be a consequen ce of decreased cell division within organ primordia. Ectopic expression of ANT under the control of the constitutive 35S promoter results in the deve lopment of larger floral organs. The number and shape of these organs is no t altered and the size of vegetative organs is normal. Microscopic and mole cular analyses indicate that the increased size of 35S::ANT sepals is the r esult of increased cell division, whereas the increased sizes of 35S::ANT p etals, stamens, and carpels are primarily attributable to increased cell ex pansion. In addition, 35S::ANT ovules often exhibit increased growth of he nucellus and the funiculus. These results suggest that ANT stimulates cell growth in floral organs. (C) 1999 Wiley-Liss, lnc.