|The SEP3 MADS-box gene belongs to a subgroup that includes SEP1 and SEP2, and all three genes are expressed early during flower development. TM5 and FBP2 represent the putative AGL9 orthologs from tomato and petunia respectively. Antisense and co-suppression phenotypes have been reported for TM5 and FBP2, and consistent with their expression patterns, the observed defects occur early in flower development within petals, stamens, and carpels.||
|AGL9 RNA (red) is first
detected late during stage 2 of flower development (below, left), shortly before the onset
expression of the organ identity MADS-box genes AGAMOUS, APETALA3, and PISTILLATA,
but after the onset of expression of the APETALA1, CAULIFLOWER, AGL2,
and AGL4 MADS-box genes.
AGL9 RNA is detected primarily in petals, stamens, and carpels, although some AGL9 RNA is also detected on the adaxial (inner) surface of sepals. AGL9 RNA becomes restricted to specific cell types later in flower development (below).
For example, AGL9 RNA does not accumulate in the sporogenous tissue that will give rise to pollen, but accumulates at high levels in anther walls and at low levels in stamen filaments. As the gynoecium develops, AGL9 expression becomes localized to the cells lining the central invagination. During stage 10, AGL9 RNA is expressed at low levels in the forming septum that divides the gynoecium and at high levels in the elongating ovule primordia.
Angenent, G.C., Franken, J., Busscher, M., Weiss, D., and van Tunen, A.J. (1994). Co-suppression of the petunia homeotic gene fbp2 affects the identity of the generative meristem. Plant J. 5, 33-44.
Mandel, A.M. and Yanofsky, M.F. (1997) The Arabidopsis AGL9 MADS-box gene is expressed in young flower primordia. Sexual Plant Reprod.
Pnueli, L., Hareven, D., Broday, L., Hurwitz, C., and Lifschitz, E. (1994). The Tm5 MADS box gene mediates organ differentiation in the three inner whorls of tomato flowers. Plant Cell, 6, 175-186.
Purugganan, M.D., Rounsley, S.D., Schmidt, R.J., and Yanofsky, M.F. (1995). Molecular evolution of flower development: diversification of the plant MADS-box regulatory gene family. Genetics 140:345-356.