GENETIC PATHWAYS CONTROLLING CARPEL DEVELOPMENT IN ARABIDOPSIS-THALIANA

Carpel development in Arabidopsis is known to be controlled by the org an identity gene AGAMOUS. However, even in the absence of AGAMOUS func tion, many carpel properties can arise suggesting that other genes are also involved, Two new carpel genes, CRABS CLAW and SPATULA, have bee n recognised by their specific disruptions to carpel development in mu tant plants. These disruptions suggest that CRABS CLAW normally plays a role in promoting the growth of specific regions of the carpel wall, whereas SPATULA apparently has a primary function in promoting develo pment of the transmitting tract, When the function of these genes is a lso compromised along with that of AGAMOUS in multiply mutant plants, carpelloid properties vanish. Thus AGAMOUS, CRABS CLAW and SPATULA act together in specifying carpel development, although none can do this alone. Because SPATULA mutants are epistatic to mutants of another car pel development gene, ETTIN, the latter may normally act by suppressin g the action of SPATULA in specific regions of the developing gynoeciu m, There is indirect evidence that ETTIN, and another morphogenetic ge ne, PINOID, act through regulating auxin-induced growth in specific re gions of the developing flower, but it is not yet known how this could result in the suppression of SPATULA function.