Genetic pathways controlling carpel development in Arabidopsis thaliana

Carpel development in Arabidopsis is known to be controlled by the organ identity gene AGAMOUS. However, even in the absence of AGAMOUS function, many carpel properties can arise suggesting that other genes are also involved. Two new carpel genes, CRABS CLAW and SPATULA, have been recognised by their specific disruptions to carpel development in mutant 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 development of the transmitting tract. When the function of these genes is also 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 carpel development gene, ETTIN, the latter may normally act by suppressing the action of SPATULA in specific regions of the developing gynoecium. There is indirect evidence that ETTIN, and another morphogenetic gene, PINOID, act through regulating auxin-induced growth in specific regions of the developing flower, but it is not yet known how this could result in the suppression of SPATULA function.