Additional Author(s): Theadora R. Tolkin, Alessandra M. Sullivan, Rainer Melzer, Günter Theißen, and Verónica S. Di Stilio
Gene Regulation: Gene Regulatory Networks; Transcriptional Control
Plant Organs: Flowers; Meristems
The Germline: Plant Life Cycle
Genetic Errors: Genetic Mutations
Evolutionary Developmental Biology: Genomic Evolution
Stage of Development: Adult
Flowers are made up of four organs: sepals, petals, stamens, and carpels. Stamens and carpels are the male and female reproductive organs of the plant, respectively. Thalictrum thalictroides (above) is a plant species that lacks petals. Its wildtype flower contains only petaloid sepals—sepals that look like petals in the sepal position (se), stamens (st), and carpels (ca).
Flower development depends on the combinatorial expression of four classes of transcription factors (A, B, C, and E). A- and E-class proteins specify sepals; A-, B-, and E-class proteins specify petals; B-, C-, and E-class proteins specify stamens; and C- and E-class proteins specify carpels and terminate floral meristem development. Mutations affecting the function of class A, B, C, and E genes are homeotic, resulting in the replacement of one organ type by another.
‘Double White’ is a sterile homeotic T. thalictroides mutant in which the stamens and carpels are replaced by sepals. When the C-class gene AGAMOUS is silenced in a wildtype T. thalictroides plant, it phenocopies the ‘Double White’ mutant. Analysis of the AGAMOUS gene in ‘Double White’ revealed the insertion of a transposable element resulting in an early stop codon. Thus, the loss of functional AGAMOUS protein is likely the cause of the double-flower phenotype in ‘Double White’.
Galimba, K.D., Tolkin, T.R., Sullivan, A.M., Melzer, R., Theissen, G., and Di Stilio, V.S. Loss of deeply conserved C-class floral homeotic gene function and C- and E-class protein interaction in a double-flowered ranunculid mutant. Proc. Natl. Acad. Sci. U.S.A, 2012, 109(34): 13478-13479.
Galimba, K.D., Tolkin, T.R., Sullivan, A.M., Melzer, R., Theissen, G., and Di Stilio, V.S. Loss of deeply conserved C-class floral homeotic gene function and C- and E-class protein interaction in a double-flowered ranunculid mutant. Proc. Natl. Acad. Sci. U.S.A, 2012, 109(34): E2267-2275.