An Evaluation of A‐Function: Evidence from theAPETALA1andAPETALA2Gene Lineages

• Published in: International journal of plant sciences Vol. 168; no. 1; pp. 73 - 91
• Main Author: Litt, Amy
• Format: Journal Article
• Language: English; Japanese
• Published: The University of Chicago Press 01.01.2007
• Subjects: Angiosperms; Calyx; Carpels; Genes; Inflorescences; Insect genetics; Meristems; Perianths; Petals; Phenotypes
• ISSN: 1058-5893; 1537-5315
• DOI: 10.1086/509662

The ABC model for the specification of floral organ identity, published 15 years ago, has proven to be a useful framework for interpreting floral development data from a wide variety of species. InArabidopsis, A‐function (specification of sepal and petal identity) is attributed to two unrelated genes,APETALA1(AP1) andAPETALA2(AP2). An examination of the available information regarding orthologues and paralogues of these genes in other species shows that although some are required for sepal identity, none is required for both sepal and petal identity. Combined with phylogenetic analyses that show gene duplication and loss specific to Brassicaceae, this suggests that the two‐whorl phenotype attributed to loss of A‐function inArabidopsismay be unique to Brassicaceae. Furthermore, all genes that are required for proper sepal identity, includingAP1andAP2, are also implicated in floral meristem identity, suggesting that these two functions may not be separable. Available data are all consistent with a previousAntirrhinum‐based model for floral organ identity that required only two gene functions. The loss of sepal identity seen in someAP1‐ andAP2‐lineage mutants can be explained as loss of floral meristem identity; the available evidence suggests that a discrete perianth identity gene function is not required.