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The SEPALLATA1 (SEP1), SEP2 and SEP3 genes were previously called AGL2, AGL4 and AGL9 respectively.  These three closely-related genes are strongly expressed in petals, stamens and carpels and their expression is first detected during stage 2 of flower development, just prior to the onset of B and C organ identity gene expression..  In addition, SEP1 an SEP2 are expressed in sepals early in flower development.


Gene Sequence

- SEP1
- SEP2
- SEP3

Map position

SEP3 Expression

The SEP1, SEP2 and SEP3 genes are functionally redundant and are required for petal, stamen and carpel development.  Triple mutant plants produce flowers that consist only of sepals.  In addition, the triple mutant flowers are indeterminate, indicating that the SEP genes are required to prevent the indeterminate growth of the flower meristem.  
The sep triple mutant is strikingly similar to double mutants lacking the B (AP3/PI) and C (AG) organ identity genes.  Taken together, the SEP gene products are required for the activity of the B and C genes.

Wild-type flowers (left) have of four whorls of organs consisting of sepals, petals, stamens and carpels.  The sep1 sep2 sep3 triple mutant (right) produces flowers that consist of a seemingly endless reiteration of sepals

Selected References:

Flanagan, C.A., and Ma, H. (1994) Spatially and temporally regulated expression of the MADS-box gene AGL2 in wild-type and mutant Arabidopsis flowers. Plant Mol. Biol.. 26:581-595.

Ma, H., Yanofsky, M.F., and Meyerowitz, E. M. (1991). AGL1-AGL6, an Arabidopsis gene family with similarity to floral homeotic and transcription factor genes. Genes Dev. 5:484-495.

Pelaz S, Ditta GS, Baumann E, Wisman E, Yanofsky MF (2000) B and C floral organ identity functions require SEPALLATA MADS-box genes. Nature 405:200-3

Savidge, B., Rounsley, S.D., and Yanofsky, M.F. (1995) Temporal relationship between the transcription of two Arabidopsis MADS-box genes and the organ identity genes. Plant Cell 7:721-733.