1. An Antagonistic Pair of FT Homologs
Mediates the Control of Flowering
Time in Sugar Beet
Presented by: Andrea Arnold, Kim Kyger, Kevona
McLaughlin, Thomas Kohlbrenner

2. Introduction
For many flowering plants, the transition from the vegetative phase to the
reproductive phase is determined by the developmental stage of the plant and
exogenous stimuli. For these plants, vernalization is a checkpoint through which they
must pass in order for flowering to occur. Vernalization is the process when, plants
pass through winter and then are exposed to lengthening days. This paper studied the
genes involved in flowering, following vernalization, in cultivated beets (Beta
vulgaris).

4. (Figure 1)
(Fig. A.) Expression of BvFT1 and BvFT2 in various tissues : seeds (se), hypocotyl (hy),
cotyledon (co), leaf (le), apex (ap), root (ro), stem (st), floral bud (bu), and flower (fl).
(Fig. B.) Expression of BvFT1 and BvFT2 in leaf samples
(Fig. C & D.) Diurnal rhythms of BvFT1 and BvFT2 in annual, biennial, and vernalized-
biennial beets.
(Fig. E.) Leaf number at the time of bolting in biennial, vernalized-biennial, and annual
plants grown under different photoperiodic conditions.
(Fig. F.) BvFT1 transcript accumulation in biennials in response to vernalization.

5. Experimental Strategies
The researchers of this article set out to address what genes are involved in
controlling flowering, following vernalization. In order to accomplish this task, the
researchers employed a number of gene manipulations and analysis such as:
● Genetic Mapping
● Complementation experiments
● Gene expression analysis
● Use of RNAi

6. (Figure 2) Misexpression of BvFT1 or BvFT2
control bolting in sugar beet. (A to C)
Nonbolting phenotype observed in BvFT2 RNAi
annual (A), BvFT1-ox annual (B), and
vernalized BvFT1-ox biennial (C) plants when
grown in LDs for 6 weeks. (Dto F) BvFT1 and
BvFT2 expression in BvFT2 RNAi (D), BvFT1-ox
(E), and vernalized BvFT-ox (F) plants (15).
Expression levels were set to unity in wild type
(WT). Error bar, mean T SE (n = 3).

7. Based on genetic mapping, complementation testing, and gene expression analysis, the researchers proposed this
gene pathway for the expression of BvFT1 function. The researchers proposed that BvFT1 expression prevents
flowering during short days and before vernalization via the repression of the BvFT2 expression. This figure
demonstrates that pathway, as well as other possible alternatives that contribute to the vernalization response
and regulation of BvFT2.

8. (Figure 4) This figure highlights the
important regions of BvFT1 and BvFT2,
shown as 3D traces with alignment diversity
color setting. The researchers used gene
expression analysis to collect and interpret
this data. When BvFT1 and BvFT2 are
compared, it is shown that both contain the
functionally important FT signatures.
However, the genes differ in the segment B
of the fourth exon, encoding an external
loop of PEBP, this is important for
vernalization. The figure demonstrates the
antagonistic functions of BvFT1 and BvFT2, in
chimeric FT proteins.

10. Results
Through the process of gene manipulations and analysis, the researchers found:
● BvFT1 prevents flowering during short days (SDs) and before
vernalization, via repression of BvFT2.
● BvFT2 is essential for flowering, as indicated by BvFT2 function
suppressed by RNAi.
● BvFT2 RNAi plants responded to vernalization and bolted after cold
treatment, though flowering was completely abolished or delayed until
very late stages.
● Sequence comparison showed that, BvFT1 and BvFT2 carry functionally
important FT signatures, Tyr85(Y) and Gln140(Q) in the segment B of
the fourth exon.
● It was also demonstrated that, BvFT1 and BvFT2 have antagonistic
functions.

11. (Figure 3) Based on genetic mapping, complementation
testing, and gene expression analysis, the researchers
proposed this gene pathway for the expression of BvFT1
function. The researchers proposed that BvFT1
expression prevents flowering during short days and
before vernalization via the repression of the BvFT2
expression. This figure demonstrates that pathway, as
well as other possible alternatives that contribute to
the vernalization response and regulation of BvFT2.

12. (Figure 2) Misexpression of BvFT1 or BvFT2 control bolting in sugar beet.
(A to C) Nonbolting phenotype observed in BvFT2 RNAi annual (A), BvFT1-
ox annual (B), and vernalized BvFT1-ox biennial (C) plants when grown in
LDs for 6 weeks. (Dto F) BvFT1 and BvFT2 expression in BvFT2 RNAi (D),
BvFT1-ox(E), and vernalized BvFT-ox (F) plants (15). Expression levels
were set to unity in wild type (WT). Error bar, mean T SE (n = 3).

13. (Figure 4) This figure highlights the important
regions of BvFT1 and BvFT2, shown as 3D traces with
alignment diversity color setting. The researchers
used gene expression analysis to collect and
interpret this data. When BvFT1 and BvFT2 are
compared, it is shown that both contain the
functionally important FT signatures. However, the
genes differ in the segment B of the fourth exon,
encoding an external loop of PEBP, this is important
for vernalization. The figure demonstrates the
antagonistic functions of BvFT1 and BvFT2, in
chimeric FT proteins.

14. Conclusion
Based on their research, the authors concluded that the gene BvFT1 inhibits flowering
before vernalization by suppressing the function of the BvFT2 gene.The researchers
found that BvFT2 RNAi responded to vernalization, and bolted after cold treatment but
flowering was unsuccessful. Further support for BvFT2 functioning to promote
flowering, when a section of BvFT2 was inserted into a section of BvFT1, flowering was
promoted. When BvFT1 was overexpressed bolting and flowering was prevented, even
after prolonged exposure to a vernalization period.

15. Reference
Pin, P., Benlloch, R., Bonnet, D., Wremerth-Weich, E., Kraft, T., Gielen, J., &
Nilsson, O. (2010). An Antagonistic Pair of FT Homologs Mediates the Control of
Flowering Time in Sugar Beet. Science, 330(6009), 1397-1400. Retrieved April
21, 2015, from http://www.sciencemag.org.proxy.library.vcu.
edu/content/330/6009/1397