Plant Cell Advance Online Publication
Published on October 26, 2007; 10.1105/tpc.107.052480
OPEN ACCESS ARTICLE
Received April 25, 2007
Returned for revision September 25, 2007
Accepted October 2, 2007
A Circadian Rhythm Set by Dusk Determines the Expression of FT Homologs and the Short-Day Photoperiodic Flowering Response in Pharbitis
Ryosuke Hayama 1, Bhavna Agashe 1, Elisabeth Luley 1, Rod King 2, and George Coupland 1*
1 Max Planck Institute for Plant Breeding Research, D-50829 Cologne, Germany
2 Commonwealth Scientific and Industrial Research Organization, Plant Industry, Canberra 2601, Australian Capital Territory, Australia
* To whom correspondence should be addressed. E-mail: coupland{at}mpiz-koeln.mpg.de.
Seasonal control of flowering through responsiveness to daylength shows extreme variation. Different species flower in response to long days or short days (SDs), and this difference evolved several times. The molecular mechanisms conferring these responses have been compared in detail only in Arabidopsis thaliana and rice (Oryza sativa) and suggest that a conserved pathway confers daylength responses through regulation of FLOWERING LOCUS T (FT) transcription by CONSTANS (CO). We studied Pharbitis (Ipomoea nil; formerly, Pharbitis nil), a widely used SD model species and a member of the Convolvulaceae, and showed using transgenic plants together with detailed expression analysis that two putative orthologs of FT (Pn FT1 and Pn FT2) promote flowering specifically under SDs. These genes are expressed only under SDs, and light flashes given during the night reduce their expression and prevent flowering. We demonstrate that in Pharbitis a circadian rhythm set by the light-to-dark transition at dusk regulates Pn FT expression, which rises only when the night is longer than 11 h. Furthermore, Pharbitis accessions that differ in their critical night-length responses express Pn FT at different times after dusk, demonstrating that natural genetic variation influencing the clock regulating Pn FT expression alters the flowering response. In these assays, Pn FT mRNA abundance was not related to Pn CO expression, suggesting that Pn FT may be regulated by a different transcription factor in Pharbitis. We conclude that SD response in Pharbitis is controlled by a dedicated light sensitive clock, set by dusk, that activates Pn FT transcription in darkness, a different mechanism for measuring daylength than described for Arabidopsis and rice.
This article has been cited by other articles:
|
|
|
|
 
M. Notaguchi, M. Abe, T. Kimura, Y. Daimon, T. Kobayashi, A. Yamaguchi, Y. Tomita, K. Dohi, M. Mori, and T. Araki
Long-Distance, Graft-Transmissible Action of Arabidopsis FLOWERING LOCUS T Protein to Promote Flowering
Plant Cell Physiol.,
November 1, 2008;
49(11):
1645 - 1658.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Pouteau, I. Carre, V. Gaudin, V. Ferret, D. Lefebvre, and M. Wilson
Diversification of Photoperiodic Response Patterns in a Collection of Early-Flowering Mutants of Arabidopsis
Plant Physiology,
November 1, 2008;
148(3):
1465 - 1473.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. W. King, T. Hisamatsu, E. E. Goldschmidt, and C. Blundell
The nature of floral signals in Arabidopsis. I. Photosynthesis and a far-red photoresponse independently regulate flowering by increasing expression of FLOWERING LOCUS T (FT)
J. Exp. Bot.,
October 3, 2008;
(2008)
ern231v1.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Compiled by, F. Tooke, T. Chiurugwi, and N. Battey
Flowering Newsletter bibliography for 2007
J. Exp. Bot.,
July 18, 2008;
(2008)
ern109v1.
[Full Text]
[PDF]
|
|
|
|
|
|
|
N. A. Eckardt
Measuring Daylength: Pharbitis Takes a Different Approach
PLANT CELL,
October 1, 2007;
19(10):
2968 - 2969.
[Full Text]
[PDF]
|
|
|
|
|
