15th International Conference on Arabidopsis Research - TAIR

T01-089
LOV1 is a floral repressor that negatively regulates
CO in Arabidopsis
So Yeon Yoo(1), Yunhee Kim(2), Jong Seob Lee(2), Ji Hoon Ahn(1)
1-1. Plant Signaling Network Research Center, School of Life Sciences and Biotechnology, Korea
University, Seoul 136-701, Korea
2-2. School of Biological Sciences, Seoul National University, Seoul 151-747, Korea
We isolated a lov1-1D (LOng Vegetative phase 1-1D) mutant that showed
late flowering phenotype in Arabidopsis from activation tagging screening
(Weigel et al., Plant Physiology 122:1003 [2000]). Late flowering of lov1-1D
is mainly contributed by prolonged all growth phases. In lov1-1D, a T-DNA
was inserted adjacent to a gene that encodes a NAC domain protein that is
homologous to petunia NAM (No Apical Meristem) (Souer et al., Cell 85:159
[1996]). RNA blot analysis showed that 35S enhancers in SKI015 increased
transcription level of the NAC domain gene. Furthermore, overexpression
of its cDNA recapitulated the original late flowering phenotype, confirming
that the gene is responsible for the late flowering phenotype. LOV1 was expressed
in early embryogenesis and in the vegetative tissues including shoot
apex later on. Because lov1-1D showed delayed flowering and LOV1 expression
was controlled in a circadian rhythmic manner, we examined expression
levels of flowering time genes within photoperiod pathway. Semiquantative
RT-PCR showed that LHY (Late Elongated Hypocotyl) and CCA1 (Circadian
Clock-Associated 1) were not affected, but expression of CO (CONSTANS)
was downregulated in lov1-1D. Furthermore FT (Flowering locus T) and SOC1
(Suppressor of CO overexpression 1), the two floral integrators downstream
of CO, were also downregulated. Constitutive expression of CO, FT, and SOC1
completely suppressed the late flowering of lov1-1D, suggesting that LOV1
is a floral repressor that negatively regulates CO in photoperiod pathway. The
role of LOV1 in determining flowering time will be further discussed.
Weigel et al., Plant Physiology 122:1003 [2000]
Souer et al., Cell 85:159 [1996]
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T01-090
Annual plant for a perennial problem
Eric Walton(1), Roger Hellens(1), Rong Mei Wu(1)
1-HortResearch, Auckland, NewZealand
The life cycle of annual plants is completed in one growing season and perenniation
is achieved through the seed. Perennial plants, not only set seed,
but produce structures (buds) that lie dormant during adverse conditions and
resume growth the following season. For both seeds and buds the timing of
growth is critical; new shoots must appear during conditions that are environmentally
acceptable. There are striking similarities between germination
in seeds and bud break in perennial plants including for example chilling
requirements and the effects of plant growth regulators, including ABA and
gibberellins. Our hypothesis is that the genes that regulate germination in
seeds are the same as those that regulate bud break.
We have shown the amino acid proline accumulates in breaking kiwifruit
buds prior to leaf emergence (1). Proline has been shown to accumulate
in germinating Arabidopsis seeds and that added proline reduces or slows
germination. Preliminary results indicate that the expression patterns of
most of the genes in the proline biosynthetic pathway are similar in breaking
kiwifruit buds and germinating Arabidopsis seeds. There is a shift from the
pentose-phosphate pathway (PPP) to glycolysis during seed germination and
bud break concurrent with the transition from heterotrophic to autotropic
growth. We are investigating the potential for Arabidopsis seed germination to
be used as a model for bud break in perennial plants.
(1) Walton et al (1998). Physiologia Plantarum 102: 171-178.
T01 Development 1 (Flower, Fertilization, Fruit, Seed)