Genetic pathways controlling carpel development inArabidopsis thaliana

Abstract

Carpel development inArabidopsis is known to be controlled by the organ identity geneAGAMOUS. 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 andSPATULA, have been recognised by their specific disruptions to carpel development in mutant plants. These disruptions suggest thatCRABS CLAW normally plays a role in promoting the growth of specific regions of the carpel wall, whereasSPATULA apparently has a primary function in promoting development of the transmitting tract. When the function of these genes is also compromised along with that ofAGAMOUS in multiply mutant plants, carpelloid properties vanish. ThusAGAMOUS, CRABS CLAW andSPATULA act together in specifying carpel development, although none can do this alone. BecauseSPATULA mutants are epistatic to mutants of another carpel development gene,ETTIN, the latter may normally act by suppressing the action ofSPATULA in specific regions of the developing gynoecium. There is indirect evidence thatETTIN, 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.