Poster: Clocks

Abs # 778: Characterization of Lemna homologues of genes related to the photoperiodic flowering

Presenter:	Miwa, Kumiko , miwa@biol1.bio.nagoya-u.ac.jp
Authors	Miwa, Kumiko  (A) (B)  Kondo, Takao  (A) (B)  Oyama, Tokitaka  (A) (B)
Affiliations:	(A): Division of Biological Science, Graduate School of Science, Nagoya University (B): Core Reserch for Evolutional Science and Technology

Plants recognize seasonal change through photoperiodic timemeasurement to regulate their flowering. Recent molecular genetic studies on a facultative long-day plant, Arabidopsis, have made considerable progress in identifying genetic pathways and molecular components associated with the control of flowering time, and the function of the circadian clock. It is thought that GI regulates photoperiodic flowering in relation to the circadian clock. The expression pattern of CO is shown to be important for promoting flowering in long day. FT is one of the early targets of CO in the photoperiod response.
Two Lemna plants, an obligatory long-day plant L.gibba G3 and an obligatory short-day plant L.paucicostata 6746, are useful plants for the study of photoperiodic flowering. Refering information of Arabidopsis, we have begun molecular analysis using Lemna plants for dissecting the mechanism of photoperiodic flowering. From L.gibba G3 and L.paucicostata 6746, we cloned homologues of GI (LgGIH1, LpGIH1), CO (LgCOH1, LpCOH1), and FT (LgFTH1, LpFTH1, LpFTH2) as genes that were possibly related to the photoperiodic flowering, APRR1/TOC1 (LgPRRH1,2,3, LpPRRH1,2,3) and CAB (LgCAB1, LpCAB1) as index genes of circadian clock, and AG (LgAGH1, LpAGH1) as that of flower development. We examined the expression of these genes in response to various photoperiods, and obtained following results. We will discuss a structure of photoperiodic flowering in Lemna.
1. CAB genes are good indexes of the circadian rhythms.
2. The expression of GI homologues showed circadian rhythm and responded to light / dark transition.
3. The expression of FT and AG homologues was increased under the photoperiodic conditions that induced flowering.