15th International Conference on Arabidopsis Research - TAIR

T02-105
The INCURVATA4 gene encodes the ATHB-15
transcription factor and is probably regulated by a
microRNA
I. Ochando(1, 3), S. Jover-Gil(2, 3), J. J. Ripoll(1), H. Candela(2), A. Vera(1), M. R.
Ponce(2), A. Martínez-Laborda(1), J. L. Micol(2)
1-División de Genética, Universidad Miguel Hernández, Campus de San Juan, 03550 Alicante,
Spain.
2-División de Genética and Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de
Elche, 03202 Elche, Alicante, Spain.
3-These authors equally contributed to this work.
Recent genetic studies in Arabidopsis thaliana have identified a number of
genes expressed in lateral organs, such as PHABULOSA (PHB) and PHAVO-
LUTA (PHV), which are probably involved in the specification of lateral organ
dorsoventrality, and encode transcription factors of the class III homeodomain/leucine
zipper (HD-Zip III) family. We have previously identified two mutants
carrying semidominant alleles of the INCURVATA4 (ICU4) gene, which
display incurved vegetative leaves, abaxial trichomes in juvenile leaves, and
abnormal fusion at the apex of the gynoecium. These weak adaxializing traits
are largely enhanced in the icu4-1 hst-1 double mutant, whose phenotype
is synergistic and includes a partial adaxialization of rosette leaves and the
transformation of the abaxial replum into an adaxial placenta with associate
ovules. The HASTY gene is known to encode a nucleocytoplasmic transporter.
We positionally cloned the ICU4 gene, which was found to encode the ATHB-
15 transcription factor, another member of the HD-Zip III family. The icu4-1
and icu4-2 semidominant, gain-of-function alleles carry the same point
mutation, which is identical to those of dominant alleles of PHB and PHV, and
affects the binding site of two microRNAs that differ in only one nucleotide,
miR165 and miR166. Our results suggest that the ICU4 gene is negatively
regulated by a microRNA and lend support to the hypothesis that HASTY
carries microRNA precursors from the nucleus to the cytoplasm.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T02-106
SCHIZORIZA is required for root patterning in
Arabidopsis
Monica Pernas(1), Eoin Ryan(1), Panaglyota Mylona(1), Paul Linstead(1), Liam
Dolan(1)
1-Department of Cell and Developmental Biology, John Innes Centre, Colney lane, Norwich NR4
7 UH, UK
Cell layers of the arabidopsis primary roots are organised in a simple radial
pattern. The root comprises concentric rings of tissue with lateral root cap
outside the epidermis, which surrounds the ground tissue ( cortex and endodermis).This
cell pattern is set up during embryogenesis and is maintained by
regular divisions of stem cells in the meristem of the developing root.
schizoriza (scz) was identified in a screen for genes involved in the development
of the root epidermis. scz develops hair cells in the subepidermal
cell layer (ground tissue) while in wild type roots they are only formed in
epidermal cells. Additionally, scz roots show supernumerary ground tissue
layers due to extra periclinal divisions in the root meristem. These mutant
phenotypes indicate that SCZ repress epidermis identity and periclinal divisions
in the ground tissue of wild type roots and that SCZ is required for the
establishment of radial organisation of tissues in the root
T02 Development 2 (Shoot, Root)