15th International Conference on Arabidopsis Research - TAIR

T02-097
MGOUN3, AN ARABIDOPSIS GENE WITH PROTEIN
INTERACTION MOTIFS IS ASSOCIATED WITH
MERISTEM ORGANIZATION AND REGULATION OF
FLOWERING TIME
GUYOMARC'H S.(1), ZHOU D.-X.(1), DELARUE M.(1)
1-Institut de Biotechnologies des Plantes. UMRS CNRS 8618. Université Paris sud. bat. 630.
91405 Orsay cedex. France
Plant growth and development depend on the activity of continuously
replenished pools of undifferentiated cells so-called meristems are complex
whose functionning is tightly regulated.
We have isolated a new Arabidopsis gene, MGOUN3 (MGO3), whose mutation
affects the structural organization and the functional regulation of both
shoot and root meristems. Four mutant alleles for this gene display severe
alterations in the regulation of the apical meristem dynamics. Indeed, during
post-embryonic development, the cell identity patterning are impaired. The
expression pattern of basic regulatory genes of the shoot apical meristem
functioning is also misshaped, consistently with the phenotypic alterations
(1). Another key feature of mgo3 mutants is their early flowering phenotype in
short days, associated with a misexpression of flowering time regulators.
MGO3 gene is unic in the Arabidopsis genome. The protein deduced from
the cDNA sequence contains TetratricoPeptide Repeats (TPR) and Leucine-
Rich Repeats (LRR), two motifs that are thought to act in protein-protein
interactions. Although MGO3 protein presents TPR as in others Arabidopsis
proteins, the MGO3 motifs are more similar to those present in LGN-related
proteins, which are regulators for some of the asymmetric cell divisions in
animal development.
Give that that mgo3 mutants are allelic to bru1 mutants which are affected
in the stability of heterochromatin organization and epigenetic gene silencing
(2), MGO3 appears as a new type of key regulators for epigenetic control
of Arabidopsis development and especially meristematic functioning and
flowering transition.
(1) Guyomarc'h S. et al. (2004) J. Exp. Bot. 55, 673-684.
(2) Takeda S. et al. (2004) Genes Dev 18, 782-93.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T02-098
Analysis of the transcriptional regulation of cell
specialisation during leaf development in Arabidopsis
thaliana
Dajana Lobbes(1), Cathie Martin(1), Jonathan Clarke(2)
1-Cell and Developmental Biology, John Innes Centre, Norwich, UK
2-John Innes Genome Lab, John Innes Centre, Norwich, UK
The objective of our project is to study the transcriptional regulation during
leaf development of Arabidopsis thaliana. The SERRATE gene which appears
to be involved in this process will be given particular emphasis within the
project. The SERRATE gene for which a mutant is already available encodes
a protein with a single C2H2 zinc finger motif. Characterisation of the serrate
mutant revealed defects in both vegetative and inflorescence phase lengths,
the timing of phase transitions, leaf shape, leaf number and phyllotaxy. The
SERRATE gene is also required for normal embryo development. The effects
of reducing or eliminating SERRATE expression on genes involved in leaf development
will be established by comparing transcript profiles of the serrate
mutant with profiles of wild type plants. Inducible expression of SERRATE
in a serrate mutant background followed by microarray-based expression
profiling will be used to identify direct targets of SERRATE. Cell-specific
expression patterns of SERRATE will be determined, firstly in wild type and
then in various mutants affecting genes which show changed expression in
the serrate mutant. The aim of these experiments will be to determine the
regulatory hierarchies controlling leaf development in Arabidopsis. A two
component expression system is being used to assess the effects of altering
SERRATE protein levels in different tissues and at different stages of plant
development. The analysis of protein-protein interactions between SERRATE
and a number of transcriptional regulators will provide us further indications
of the function of SERRATE.
Clarke J.H. et al. (1999) Plant Journal, 20: 493-501
Prigge M.J. & Wagner D.R. (2001) The Plant Cell, 13: 1263-1279
T02 Development 2 (Shoot, Root)