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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

AqTFL1 and AqAGL24.2 in situ expression patterns. AqTFL1 expression in four-week (A) and six-week (B, C) vernalized apices. AqAGL24.2 expression in six-week (D, E) vernalized apices and in a higher order post vernalized inflorescence (F). Ap = apical meristem, Ax = axillary meristem, Lax = leaf axillary meristem, lf = leaf, b = bract, sp = sepal, open arrowheads indicate petal and stamen primordia, arrows indicate AqAGL24 expression in leaves. Scale bar = 100 μm A-C; 50 μm D-F.
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Figure 5: AqTFL1 and AqAGL24.2 in situ expression patterns. AqTFL1 expression in four-week (A) and six-week (B, C) vernalized apices. AqAGL24.2 expression in six-week (D, E) vernalized apices and in a higher order post vernalized inflorescence (F). Ap = apical meristem, Ax = axillary meristem, Lax = leaf axillary meristem, lf = leaf, b = bract, sp = sepal, open arrowheads indicate petal and stamen primordia, arrows indicate AqAGL24 expression in leaves. Scale bar = 100 μm A-C; 50 μm D-F.

Mentions: PHYA and PHYB as well as CRY1 and CRY2 orthologs from Aquilegia were identified (See Additional File 2: Figure 5). A search of the Aquilegia DFCI Gene Index did not reveal any homologs to the circadian clock gene TOC1 but sequence fragments with similarity to CCA1 and LHY were obtained (DT742775, TC22162). These were not pursued further since the core circadian clock is not the focus of this study. We also recovered 5' and 3' ends of an apparent Aquilegia GI ortholog, termed AqGI, and these regions were used to obtain the complete cDNA sequence using RT-PCR. Similar to LFY, the lineage evolution of GI is rather straightforward and phylogenetic analyses support our identification of AqGI as orthologous to Arabidopsis GI (See Additional File 2: Figure 6).


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

Ballerini ES, Kramer EM - Evodevo (2011)

AqTFL1 and AqAGL24.2 in situ expression patterns. AqTFL1 expression in four-week (A) and six-week (B, C) vernalized apices. AqAGL24.2 expression in six-week (D, E) vernalized apices and in a higher order post vernalized inflorescence (F). Ap = apical meristem, Ax = axillary meristem, Lax = leaf axillary meristem, lf = leaf, b = bract, sp = sepal, open arrowheads indicate petal and stamen primordia, arrows indicate AqAGL24 expression in leaves. Scale bar = 100 μm A-C; 50 μm D-F.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: AqTFL1 and AqAGL24.2 in situ expression patterns. AqTFL1 expression in four-week (A) and six-week (B, C) vernalized apices. AqAGL24.2 expression in six-week (D, E) vernalized apices and in a higher order post vernalized inflorescence (F). Ap = apical meristem, Ax = axillary meristem, Lax = leaf axillary meristem, lf = leaf, b = bract, sp = sepal, open arrowheads indicate petal and stamen primordia, arrows indicate AqAGL24 expression in leaves. Scale bar = 100 μm A-C; 50 μm D-F.
Mentions: PHYA and PHYB as well as CRY1 and CRY2 orthologs from Aquilegia were identified (See Additional File 2: Figure 5). A search of the Aquilegia DFCI Gene Index did not reveal any homologs to the circadian clock gene TOC1 but sequence fragments with similarity to CCA1 and LHY were obtained (DT742775, TC22162). These were not pursued further since the core circadian clock is not the focus of this study. We also recovered 5' and 3' ends of an apparent Aquilegia GI ortholog, termed AqGI, and these regions were used to obtain the complete cDNA sequence using RT-PCR. Similar to LFY, the lineage evolution of GI is rather straightforward and phylogenetic analyses support our identification of AqGI as orthologous to Arabidopsis GI (See Additional File 2: Figure 6).

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