Proceedings of the XLVII
Italian Society of Agricultural Genetics - SIGA Annual Congress
Verona,
Italy - 24/27 September, 2003
ISBN 88-900622-4-X
Poster
Abstract - 1.04
CHARACTERIZATION
OF PUTATIVE UPSTREAM REGULATORS OF BKN3,
THE BARLEY HOMEOBOX GENE RESPONSIBLE FOR HOODED MUTATION
M.R.
STILE*, L. SANTI**, L. ROSSINI***, C. POZZI****, M. OSNATO***, Y. LIU**, E.
FILIPPONE*, F. SALAMINI**
*) Department of
Soil, Plant and Environmental Sciences–School of Biotechnological Sciences,
University of Naples, Portici, Italy
**)
Max-Planck-Institute for Plant Breeding Research, Carl-von-Linnè-weg 10,
50827 Colo gne, Germany
***)
University of Milan, Dipartimento di Produzione Vegetale, Via Celoria 2, 20133
Milan, Italy
****)
Fondazione Parco Tecnologico Padano, V. Haussmann 11, 26900 Lodi, Italy
barley mutant,
Shoot Apical Meristem, Knox genes
Molecular
and genetic analyses have revealed a subfamily of homeobox-containing genes, Knox (Knotted1-like
homeobox) genes that play a vital role in meristem function. Knox activity has been proposed to maintain
an indeterminate state in the cells of the shoot apical meristem (SAM). In
agreement with this model, Knox genes are specifically expressed in
the central region of the SAM and are repressed in lateral organ primordia.
Knox
gene function may require the cooperation of, or be inhibited by, other
factors that are expressed in a spatially or temporally restricted pattern
during development. Loci that regulate Knox expression have
been isolated and characterized in both dicot and monocot species, e.g. phantastica
(phan) in Antirrhinum (Waites e Hudson, 1995) and rough-sheath2 (rs2) in maize (Schneeberger et al., 1998). The phenotypes of phan and rs2
recessive mutants resemble those conditioned by gain-of-function
mutations in Knox genes, suggesting that phan and rs2 act
as repressors of Knox gene expression. So far regulators of Knox genes
have been characterized by mutant analysis, but no molecular evidence has been
reported for the direct role of these proteins in the control of Knox gene
expression.
In
barley, the dominant Hooded phenotype is caused by the
duplication of a 305bp element in the IV intron of Bkn3, a Knox gene.
This element has been used as a bait in a yeast one hybrid screen aimed at
identifying putative DNA-binding proteins involved in Bkn3
regulation. This approach led to the isolation of four barley cDNAs, B42, B65,
B89, and BBR (Barley B Recombinant, Santi et
al., 2003).
In
order to gather insight into how these proteins interact with the
305bp intron sequence, we have undertaken the molecular characterization of
these barley genes. Genomic and full-length cDNA sequences have been determined
and all four genes have been positioned on the established AFLP/RFLP/ISTR
linkage map (Castiglioni et al., 1998). Transcript levels for the four genes were compared in wild-type and Hooded
barley tissues. Yeast two hybrid assays, conducted with partial and full
length cDNA sequences, revealed selective interactions between the proteins.
RFP fusion constructs of all four proteins exhibited nuclear localization in
tobacco protoplasts, consistent with their putative role in the transcriptional
regulation of Bkn3.
References:
Castiglioni et
al., 1998, Genetics, 149:2039-2056
Santi et al.,
2003, Plant Journal, 34:813-826
Schneeberger et
al., 1998, Development, 125:2857-2865
Waites e Hudson,
1995, Development, 121:2143-2154.