15th International Conference on Arabidopsis Research - TAIR

T01-091
Functional analysis of a phosphatidic acid in ABA
signaling during germination
Takeshi Katagiri(1), Masatomo Kabayashi(2), Kazuo Shinozaki(1)
1-Plant Molecular Biology Laboratory, RIKEN Tsukuba Institute
2-Experimental Plant Division, RIKEN Bioresouce Center
The hormone abscisic acid (ABA) regulates developmental processes and
stress responses in plants. In this study we analyzed a role of a phosphatidic
acid (PA) in ABA signal transduction during seed germination. A physiological
analysis showed PA triggers early signal transduction events that lead to the
ABA responses during seed germination.
To examine the possible function of PA during germination, we measured
PA production, and found that PA increased. Phosphatidic acid phosphatase
(PAP) is an enzyme that catalyzes PA to diacylglycerol. We analyzed a role of
PAP in PA signaling during germination. There are four genes for Arabidopsis
genome. To identify functional PAP genes during germination process, we
analyzed expression of the four PAP genes and phenotypes of their knockout
mutants. The PAP-knockout plant revealed a hypersensitive phenotype to
ABA and accumulated PA during germination. These results suggest that PAP
is involved in ABA signaling during seed germination.
T01 Development 1 (Flower, Fertilization, Fruit, Seed)
T01-092
Analysis of sepal and petal development using fl51
mutant of Arabidopsis
Noriyoshi Yagi(1), Seiji Takeda(1), Ryuji Tsugeki(1), Kiyotaka Okada(1, 2)
1-Department of Botany, Graduate School of Science, Kyoto University
2-CREST, Japan Science and Technology Agency
Arabidopsis flowers are composed of four types of floral organs, four sepals,
four petals, six stamens, and two fused carpels. Each type of organ forms in
a concentric whorl. It is well known that the organ identity is established in
concentric pattern by floral homeotic genes. On the other hand, floral organ
position is defined in each whorl in relation to a putative axis in the floral
meristem, indicating regulatory mechanisms controlling the position of floral
organ within each whorl. For proper development of floral organs, primordia
formation and growth such as differentiation and proliferation of cells are to
be strictly controlled. However, these developmental processes are not well
understood. To identify the genes and mechanisms controlling primordia
formation and growth, we are analyzing fl51 mutant showing defects in sepal
and petal development.
In fl51, four sepals and petals are narrower and longer than those of wild
type, though their identities are normal. Sepals are sometimes fused along
their edges towards the base. Lateral sepal primordia are smaller than those
of wild type, and their position shifted toward either the abaxial or adaxial
sepal primordium. By positional cloning, we found that FL51 gene encoded
a protein that was a component of the spliceosome. This suggests that FL51
protein is required for mRNA splicing of genes involved in the formation and
growth of primordia of sepals and petals. An RT-PCR assay revealed that
FL51 gene was expressed in almost all tissue, though the abnormalities in
fl51 are confined to sepals and petals. In fl51, a nucleotide change occurred
at the splice donor site, resulting in miss splicing. From database search, in
addition to FL51 gene, one FL51-related gene was found in Arabidopsis.
We are examining the spatial and temporal expression patterns of FL51
gene in inflorescences by mRNA in situ hybridization. We are also analyzing
the phenotype of T-DNA insertion lines of FL51 to investigate differences in
the effect to floral organ development between severe alleles with weak ones
of fl51 mutants. In addition, we investigate the relationship between FL51
gene and other floral genes by using double mutants. The phenotype of fl51,
expression and function of FL51 will be presented.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin