Byzova et al. (1999): A recessive mutation in the Arabidopsis STERILE APETALA (SAP) causes severe aberrations in inflorescence and flower and ovule development. In sap flowers, sepals are carpelloid, petals are short and narrow or absent, and anthers are degenerated. Megasporogenesis, the process of meiotic divisions preceding the female gametophyte formation, is arrested in sap ovules during or just after the first meiotic division. More severe aberrations were observed in double mutants between sap and mutant alleles of the floral homeotic gene APETALA2 (AP2) suggesting that both genes are involved in the initiation of female gametophyte development. Together with the organ identity gene AGAMOUS (AG) SAP is required for the maintenance of floral identity acting in a manner similar to APETALA1. In contrast to the outer two floral organs in sap mutant flowers, normal sepals and petals develop in ag/sap double mutants, indicating that SAP negatively regulates AG expression in the perianth whorls. This supposed cadastral function of SAP is supported by in situ hybridization experiments showing ectopic expression of AG in the sap mutant. We have cloned the SAP gene by transposon tagging and revealed that it encodes a novel protein with sequence motifs, that are also present in plant and animal transcription regulators. Consistent with the mutant phenotype, SAP is expressed in inflorescence and floral meristems, floral organ primordia, and ovules. Taken together, we propose that SAP belongs to a new class of transcription regulators essential for a number of processes in Arabidopsis flower development.


Byzova, MV; Franken, J; Aarts, MG; de Almeida-Engler, J; Engler, G; Mariani, C; Van Lookeren Campagne, MM; Angenent, GC. 1999. Arabidopsis STERILE APETALA, a multifunctional gene regulating inflorescence, flower, and ovule development. Genes Dev. 13(8):1002-14 PubMed


Name: SAP
Class: TF
Number of species containing the TAP: 62
Number of available proteins: 81

The colour code corresponds to the rules for the domains:

should be contained
should not be contained

Domain rules:

(Domain names are clickable)

Phylogenetic tree for Archeaplastida:

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TAP distribution:

The following table shows the distribution of SAP over all species included in TAPscan. The values for e.g. a specific kingdom are shown in the tree below if you expand the tree for that kingdom.

Minimum Maximum Average Median Standard deviation

List of species containing SAP sorted by kingdomcladesupergrouporderfamily:

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expand kingdom Archaeplastida (82 proteins in 62 species)
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A list of species letter codes included in the protein names can be found here (opens in new tab).