Patterning of Inflorescences and Flowers by the F-Box Protein DOUBLE TOP and the LEAFY Homolog ABERRANT LEAF AND FLOWER of Petunia

Abstract

Angiosperms display a wide variety of inflorescence architectures differing in the positions where flowers or branches arise. The expression of floral meristem identity (FMI) genes determines when and where flowers are formed. In Arabidopsis thaliana, this is regulated via transcription of LEAFY (LFY), which encodes a transcription factor that promotes FMI. We found that this is regulated in petunia (Petunia hybrida) via transcription of a distinct gene, DOUBLE TOP (DOT), a homolog of UNUSUAL FLORAL ORGANS (UFO) from Arabidopsis. Mutation of DOT or its tomato (Solanum lycopersicum) homolog ANANTHA abolishes FMI. Ubiquitous expression of DOT or UFO in petunia causes very early flowering and transforms the inflorescence into a solitary flower and leaves into petals. Ectopic expression of DOT or UFO together with LFY or its homolog ABERRANT LEAF AND FLOWER (ALF) in petunia seedlings activates genes required for identity or outgrowth of organ primordia. DOT interacts physically with ALF, suggesting that it activates ALF by a posttranslational mechanism. Our findings suggest a wider role than previously thought for DOT and UFO in the patterning of flowers and indicate that the different roles of LFY and UFO homologs in the spatiotemporal control of floral identity in distinct species result from their divergent expression patterns.

Expression Level ofABERRANT PANICLE ORGANIZATION1Determines Rice Inflorescence Form through Control of Cell Proliferation in the Meristem

“…Recently, physical interactions between UFO and LFY in Arabidopsis and between DOT and ABERRANT LEAF AND FLOWER (ALF), the petunia LFY, in petunia have been demonstrated (Chae et al, 2008;Souer et al, 2008). The UFO/LFY complex is recruited to the promoter of the LFY target genes to induce transcription.…”

“…floral) identity in the meristem, is opposite to that of APO1 counterparts. All UFO orthologs in dicot species reported so far promote floral fates (Simon et al, 1994;Levin and Meyerowitz, 1995;Taylor et al, 2001;Zhang et al, 2003;Lippman et al, 2008;Souer et al, 2008).…”

“…Basically, conserved systems driven by LFY/UFO orthologs control floral meristem identity in Antirrhinum and petunia (Petunia hybrida) although minor divergences in their mode of operation are observed. For example, DOUBLE TOP (DOT), a UFO ortholog, is the major determinant of floral meristem identity in petunia, whereas, in Arabidopsis and Antirrhinum, LFY and FLORICAULA (FLO) are major players that determine floral meristem identity (Weigel et al, 1992;Simon et al, 1994;Souer et al, 2008). Mutations in UFO or FIMBRIATA (FIM), an Antirrhinum UFO ortholog, confer only subtle effects on floral development.…”

“…Surprisingly, UFO and all its orthologs in dicot species reported so far including FIM, DOT, Proliferating Floral Organs, ANANTHA (AN), and Stamina pistillaoida promote floral fate, whereas ABERRANT PANICLE ORGANIZATION1 (APO1), a rice UFO ortholog, suppresses floral fate (Simon et al, 1994;Levin and Meyerowitz 1995;Souer et al, 1998Souer et al, , 2008Taylor et al, 2001;Zhang et al, 2003;Ikeda et al, 2007;Lippman et al, 2008). apo1 loss-of-function mutant plants exhibit precocious transition of the IM and rachis branch meristems into spikelet meristems, leading to formation of small inflorescences (Ikeda et al, , 2007.…”

Genetic Control and Evolution of Anthocyanin Methylation

“…Normalization was done based on the expression of ACTIN. Because MF1 (DIFe2a) and MF2 (DIFe2b) mRNAs were difficult to distinguish with primers suitable for real-time PCR, we used a previously described quantitative reverse transcription (RT)-PCR procedure (Souer et al, 2008) instead. This involved the amplification of specific mRNA products with gene-specific primers (Supplemental Table S7) using a reduced number of amplification cycles (20-25, depending on the abundance of the mRNA), to avoid reaching saturation and ensure a linear response, and detection of PCR products by DNA gel-blot hybridization with 32 P-labeled cDNA probes and phosphorimaging, which ensures a quantitative detection of PCR products.…”