CYCLOIDEA gene activity, local growth and curvature in the dorsal petal of Lathyrus odoratus (Fabaceae)

Abstract

ABSTRACTThe hooded (hdd) floral mutant of sweet pea (Lathyrus odoratus L.) is apparently caused by loss of function of the floral developmental gene CYCLOIDEA (CYC). It has a concavely folded dorsal petal (standard) compared to the more or less flat standard of the wild type. To examine localised growth differences in wild type and hdd flowers, we printed fine-scale grids on the surfaces of sweet pea buds using inkjet technology. Wild-type standard petals have a more uniform rate of growth, whereas hdd standard petals show increased growth at their margins. The resultant lamina/margin growth differential leads to negative Gaussian curvature and can account for the differences in curvature between wild-type and hdd petals. We conclude that CYC has a role in the negative regulation of marginal petal growth in Lathyrus in order to maintain dorsal petal flatness. Differences in CYC expression and activity could possibly contribute to the range of dorsal petal form seen throughout the Fabaceae.