T. Ito et Em. Meyerowitz, Overexpression of a gene encoding a cytochrome p450, CYP78A9, induces large and seedless fruit in arabidopsis, PL CELL, 12(9), 2000, pp. 1541-1550
An activation tagging screen in which the cauliflower mosaic virus 35S enha
ncer was inserted randomly into an Arabidopsis genome homozygous for the fl
oral homeotic mutation apetala2-1 (ap2-1) resulted in a line (28-5) with ex
traordinarily wide, heart-shaped ovaries. The ovary of the 28-5 ap2-1 mutan
t shows an oval shape because of increased numbers of enlarged cells. When
the ap2-1 mutation is crossed out of the genetic background, more elongated
rather than wider fruits are obtained. Normally, Arabidopsis fruits will d
evelop to a normal size only when the ovules are present and fertilized. In
the 28-5 single mutant, the siliques keep growing despite failure of ferti
lization and can reach nearly normal size. When wild-type pollen was used t
o pollinate the mutant pistil, the pollinated 28-5 silique became >10% long
er and 40% wider than a wild-type silique, although producing very few seed
s. The enhancer insertion in line 28-5 acts by hyperactivating a cytochrome
P450 gene, CYP78A9. The pistil of 28-5 ap2-1 mutant flowers shows a struct
ure similar to that of Capsella bursa-pastoris, a distant mustard relative
of Arabidopsis, suggesting that the processes regulated by the CYP78A9-enco
ded protein may be involved in evolutionary control of carpel shape.