OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 19/10/2988    most recent tpc.107.052480v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Cell Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (26) Citing Articles via Google Scholar Google Scholar Articles by Hayama, R. Articles by Coupland, G. Search for Related Content PubMed PubMed Citation Articles by Hayama, R. Articles by Coupland, G. Agricola Articles by Hayama, R. Articles by Coupland, G.

A Circadian Rhythm Set by Dusk Determines the Expression of FT Homologs and the Short-Day Photoperiodic Flowering Response in Pharbitis^[W],[OA]

^a Max Planck Institute for Plant Breeding Research, D-50829 Cologne, Germany
^b Commonwealth Scientific and Industrial Research Organization, Plant Industry, Canberra 2601, Australian Capital Territory, Australia

¹ Address correspondence to 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.

Related articles in Plant Cell:

Measuring Daylength: Pharbitis Takes a Different Approach

Nancy A. Eckardt
Plant Cell 2007 19: 2968-2969. [Full Text]  

This article has been cited by other articles:

				L. C. Liew, V. Hecht, R. E. Laurie, C. L. Knowles, J. K. Vander Schoor, R. C. Macknight, and J. L. Weller DIE NEUTRALIS and LATE BLOOMER 1 Contribute to Regulation of the Pea Circadian Clock PLANT CELL, October 1, 2009; 21(10): 3198 - 3211. [Abstract] [Full Text] [PDF]

				C.-J. Hou and C.-H. Yang Functional Analysis of FT and TFL1 Orthologs from Orchid (Oncidium Gower Ramsey) that Regulate the Vegetative to Reproductive Transition Plant Cell Physiol., August 1, 2009; 50(8): 1544 - 1557. [Abstract] [Full Text] [PDF]

				C. C. Zheng, D. Potter, and S. D. O'Neill Phytochrome gene expression and phylogenetic analysis in the short-day plant Pharbitis nil (Convolvulaceae): Differential regulation by light and an endogenous clock Am. J. Botany, July 1, 2009; 96(7): 1319 - 1336. [Abstract] [Full Text] [PDF]

				U. Lagercrantz At the end of the day: a common molecular mechanism for photoperiod responses in plants? J. Exp. Bot., July 1, 2009; 60(9): 2501 - 2515. [Abstract] [Full Text] [PDF]

				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]