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

Ballerini ES, Kramer EM - Evodevo (2011)

Bottom Line: 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).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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept, of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave,, Cambridge, MA, 02138, USA. ekramer@oeb.harvard.edu.

ABSTRACT

Background: Flowering 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.

Results: We 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.

Conclusions: In 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.

No MeSH data available.


Related in: MedlinePlus

Flowering time of A. formosa in different light regimes and meristematic development during vernalization. (A) Flowering time of A. formosa plants grown under three different light/temperature regimes: constant SD with eight weeks of 4°C, LD with eight weeks of 4°C SD, or LD with eight weeks of 20°C SD. Day 1 is the first day that vernalized plants were removed from vernalization and LD non-vernalized plants were moved back into LD. Time to flowering was measured as the number of days following removal from vernalization when an inflorescence was visible above the leaf crown. The x-axis after 85 days when the experiment was ended. (B) A. formosa meristem development through vernalization. The SAM just prior to vernalization (Pre), two weeks into vernalization (two weeks), six weeks (six weeks) into vernalization, eight weeks into vernalization (eight weeks), and one week following vernalization (one week post).
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Figure 2: Flowering time of A. formosa in different light regimes and meristematic development during vernalization. (A) Flowering time of A. formosa plants grown under three different light/temperature regimes: constant SD with eight weeks of 4°C, LD with eight weeks of 4°C SD, or LD with eight weeks of 20°C SD. Day 1 is the first day that vernalized plants were removed from vernalization and LD non-vernalized plants were moved back into LD. Time to flowering was measured as the number of days following removal from vernalization when an inflorescence was visible above the leaf crown. The x-axis after 85 days when the experiment was ended. (B) A. formosa meristem development through vernalization. The SAM just prior to vernalization (Pre), two weeks into vernalization (two weeks), six weeks (six weeks) into vernalization, eight weeks into vernalization (eight weeks), and one week following vernalization (one week post).

Mentions: We note that LD grown plants differed in appearance from their SD-grown siblings in that the latter showed much less leaflet and petiole expansion (See Additional File 1: Figure 1). On average, plants grown in SD took slightly longer to flower than plants grown in LD with mean days to flowering of 28.6 and 24.1 respectively, not including three SD plants that did not flower (Figure 2A). When the three non-flowering SD plants are included in a rank test analysis, the median flowering time three plants grown in SD and LD is 29 and 20 days, respectively, and the distribution of flowering time differs significantly (Mann-Whitney U = 2.3, n1 = 25, n2 = 20, P < 0.5 two-tailed). Dropping the three plants that did not flower, the median flowering time of SD plants drops to 26 days and the distributions of flowering time between SD and LD grown plants no longer differ significantly (Mann-Whitney U = 1.8, n1 = 22, n2 = 20, P > 0.5 two-tailed).


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

Ballerini ES, Kramer EM - Evodevo (2011)

Flowering time of A. formosa in different light regimes and meristematic development during vernalization. (A) Flowering time of A. formosa plants grown under three different light/temperature regimes: constant SD with eight weeks of 4°C, LD with eight weeks of 4°C SD, or LD with eight weeks of 20°C SD. Day 1 is the first day that vernalized plants were removed from vernalization and LD non-vernalized plants were moved back into LD. Time to flowering was measured as the number of days following removal from vernalization when an inflorescence was visible above the leaf crown. The x-axis after 85 days when the experiment was ended. (B) A. formosa meristem development through vernalization. The SAM just prior to vernalization (Pre), two weeks into vernalization (two weeks), six weeks (six weeks) into vernalization, eight weeks into vernalization (eight weeks), and one week following vernalization (one week post).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3049749&req=5

Figure 2: Flowering time of A. formosa in different light regimes and meristematic development during vernalization. (A) Flowering time of A. formosa plants grown under three different light/temperature regimes: constant SD with eight weeks of 4°C, LD with eight weeks of 4°C SD, or LD with eight weeks of 20°C SD. Day 1 is the first day that vernalized plants were removed from vernalization and LD non-vernalized plants were moved back into LD. Time to flowering was measured as the number of days following removal from vernalization when an inflorescence was visible above the leaf crown. The x-axis after 85 days when the experiment was ended. (B) A. formosa meristem development through vernalization. The SAM just prior to vernalization (Pre), two weeks into vernalization (two weeks), six weeks (six weeks) into vernalization, eight weeks into vernalization (eight weeks), and one week following vernalization (one week post).
Mentions: We note that LD grown plants differed in appearance from their SD-grown siblings in that the latter showed much less leaflet and petiole expansion (See Additional File 1: Figure 1). On average, plants grown in SD took slightly longer to flower than plants grown in LD with mean days to flowering of 28.6 and 24.1 respectively, not including three SD plants that did not flower (Figure 2A). When the three non-flowering SD plants are included in a rank test analysis, the median flowering time three plants grown in SD and LD is 29 and 20 days, respectively, and the distribution of flowering time differs significantly (Mann-Whitney U = 2.3, n1 = 25, n2 = 20, P < 0.5 two-tailed). Dropping the three plants that did not flower, the median flowering time of SD plants drops to 26 days and the distributions of flowering time between SD and LD grown plants no longer differ significantly (Mann-Whitney U = 1.8, n1 = 22, n2 = 20, P > 0.5 two-tailed).

Bottom Line: 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).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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept, of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave,, Cambridge, MA, 02138, USA. ekramer@oeb.harvard.edu.

ABSTRACT

Background: Flowering 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.

Results: We 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.

Conclusions: In 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.

No MeSH data available.


Related in: MedlinePlus