Environmental and molecular analysis of the floral transition in the lower eudicot Aquilegia formosa

Abstract

BackgroundFlowering is a critical transition in plant development, the timing of which can have considerable fitness consequences. Until recently, research into the genetic control of flowering time and its associated developmental changes was focused on core eudicots (for example, Arabidopsis) or monocots (for example, Oryza). Here we examine the flowering response of Aquilegia formosa, a member of the eudicot order Ranunculales that is emerging as an important model for the investigation of plant ecology and evolution.ResultsWe have determined that A. formosa has a strong vernalization requirement but little or no photoperiod response, making it a day neutral (DN) plant. Consistent with this, the Aquilegia homolog of FLOWERING LOCUS T (AqFT) is expressed in both long and short days but surprisingly, the locus is expressed before the transition to flowering. In situ hybridizations with homologs of several Arabidopsis Floral Pathway Integrators (FPIs) do not suggest conserved functions relative to Arabidopsis, the potential exceptions being AqLFY and AqAGL24.2.ConclusionsIn Aquilegia, vernalization is critical to flowering but this signal is not strictly required for the transcriptional activation of AqFT. The expression patterns of AqLFY and AqAGL24.2 suggest a hypothesis for the development of Aquilegia's determinate inflorescence whereby their differential expression controls the progression of each meristem from inflorescence to floral identity. Interestingly, none of the Aquilegia expression patterns are consistent with a function in floral repression which, combined with the lack of a FLC homolog, means that new candidate genes must be identified for the control of vernalization response in Aquilegia.

Turned on by heat: differential expression of FT and LFY-like genes in Narcissus tazetta during floral transition

“…Following major breakthroughs in understanding flowering biology in model species, the homologues of several key flowering genes have also been found in geophyte and herbaceous species. For example, LFY homologues have been isolated from Allium sativum ( gaLFY ; Rotem et al , 2007, 2011), N. tazetta ( NLF ; Noy-Porat et al , 2010), and Aquilegia formosa ( AqLFY ; Ballerini and Kramer, 2011). FT -like AcFTL has been found in onion ( Allium cepa ) (Taylor, 2009; Taylor et al , 2010).…”

“…In the perennial herbaceous A. formosa , the FT homologue AqFT is expressed before the transition to flowering under both long-day and short-day conditions. Although vernalization is critical to flowering in Aquilegia , low temperature is not strictly required for the transcriptional activation of AqFT (Ballerini and Kramer, 2011). In the present experiments, floral induction in N. tazetta occurred either when bulbs remained underground with no foliage leaves or active roots, or during bulb storage at high temperatures in complete darkness.…”

Crop plants as models for understanding plant adaptation and diversification

“…The Arabidopsis flowering time pathway is represented as a simplified schematic based on Ballerini and Kramer (2011) and references in Table 2; photoperiod response occurs under long-day (LD) conditions. The gray inset shows a simplified schematic of the rice photoperiod response pathway and immediate downstream genes ( Hd3a and RFT1 , both Arabidopsis FT homologs), based on Tsuji et al (2011) and references in Table 2.…”

Molecular basis for three-dimensional elaboration of theAquilegiapetal spur

“…Results were visualized in the Harvard Center for Biological Imaging on a Zeiss AxioImager Z2 microscope. Developmental floral stages were classified according to Ballerini & Kramer [32] as reported in electronic supplementary material, table S2. The position of the presumptive nectary can be determined by comparing serial sections and identifying the sections that contain the longest extent of the developing spur.…”