THE ARABIDOPSIS SUPERMAN GENE MEDIATES ASYMMETRIC GROWTH OF THE OUTERINTEGUMENT OF OVULES

Arabidopsis superman (sup, also referred to as floral mutant10) mutant s have previously been shown to have flowers with supermumerary stamen s and reduced carpels as a result of ectopic expression of the floral homeotic gene APETALA3 (AP3). Here, we report that sop mutations also cause specific alterations in ovule development. Growth of the outer i ntegument of wild-type ovules occurs almost exclusively on the abaxial side of the ovule, resulting in a bilaterally symmetrical hoodlike st ructure. In contrast, the outer integument of sup mutant ovules grows equally on all sides of the ovule, resulting in a nearly radially symm etrical tubular shape. Thus, one role of SUP is to suppress growth of the outer integument on the adaxial side of the ovule. Genetic analyse s showed that the effects of sup mutations on ovule development are in dependent of the presence or absence of AP3 activity. Thus, SUP acts t hrough different mechanisms in its early role in ensuring proper deter mination of carpel identity and in its later role in asymmetric suppre ssion of outer integument growth.