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Research: Project

Characterisation of different sepallata mutants and their effect on flower development in Arabidopsis thaliana

Sandra Biewers, University of Leeds

SEPALLATA genes (SEP1–4) belong to the MADS-box transcription factor family and are required for the development and specification of all four floral organ types (sepals, petals, stamens and carpels) and for floral determinacy. The triple mutant (sep1/2/3) flowers are composed only of sepals while flowers of the quadruple mutant (sep1/2/3/4) produce leaves only[1-3]. These findings reveal the important function of all four SEP genes in sepal, petal, stamen and carpel development. The SEP gene family establishes the floral context by acting as a co–factor providing flower–specific activity to the ABC genes by making complexes with their products. SEP proteins are described as “bridges” that mediate the formation of quartet complexes specifying floral organ identity. The target genes regulated by the range of different E–class–containing complexes is still unclear.

The aim of this project is to identify targets of SEPs that are bound and regulated by MADS Box proteins in early stages of floral organ development. Chromatin Immunoprecipitation experiments with subsequent deep sequencing (ChIP-SEQ) will be performed on floral tissues at different developmental stages in complemented sep mutant plants to obtain sequence data on DNA binding sites of SEPs.

Furthermore we will analyse the function of SEP1, SEP2, SEP3 and SEP4 during flower development in different floral organs and tissues at variable stages. For this purpose we use different mutants like T-DNA insertion lines, Tilling lines and transposable elements.

Fig 1. Flowers of sep3 single and sep1sep2sep3 triple mutant. (a) a sep3 single mutant with a slightly twisted petal. (b) a sep1sep2sep3 triple mutant flower. Sepals replace all floral organs

Figure 1

References:

[1] Pelaz S, D.G., Baumann E, Wisman E, Yanofsky MF., B and C organ identity functions requiere SEPALLATA Mads-box genes. Nature, 2000. 405: p. 200-203.

[2] Ditta G, P.A., Robles P, Pelaz S, Yanofsky MF., The SEP4 gene of Arabidopsis thaliana functions in floral organ and meristem identity. Curr Biol. , 2004.

[3] Takashi Honma, K.G., Complexes of MADS-box proteins are sufficient to convert leaves into floral organs. Nature, 2001. 409: p. 525-529.

[4] Kaufmann K, M.J., Jauregui R, Airoldi CA, Smaczniak C, Krajewski P, Angenent GC., Target genes of the MADS transcription factor SEPALLATA3: integration of developmental and hormonal pathways in the Arabidopsis flower. PLoS Biol, 2009 Apr 7(4):e1000090.