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RESEARCH INTERESTS
Molecular genetics of leaf vein pattern development in Arabidopsis
Genetic dissection of leaf and cotyledon vein patterning in Arabidopsis
Molecular analysis of vein patterning genes
Genetic and molecular characterization of leaf initiation
PUBLICATIONS
Posters
Genetic mechanisms controlling vein pattern in Arabidopsis
Lignin-deficient Arabidopsis mutants
The goal of research in my lab is to understand the genetic
and molecular basis for vein patterning in plants. Each
organ type within a plant has a specific stereotypical
pattern of veins. We are focusing on leaf vein patterning
because the leaf has the most critical need for normal
pattern establishment.
Wild-type Arabidopsis vein patterns are shown in the
figure below. Cotyledons, leaf-like organs formed during
embryogenesis, have a simple vein pattern; the primary
vein runs along the center of the organ, and the four
secondary veins branch from the primary vein, and rejoin to
form four loops. Leaves contain primary, secondary, and
tertiary veins, which together form a reticulated pattern.
Although we know a lot about vein anatomy and function,
almost nothing is known about how patterns of veins are
established.
To identify the genes that function in vein patterning, we
are carrying out genetic and molecular characterizations of
Arabidopsis mutants. We have 45 Arabidopsis mutants
with vein pattern defects, and we have placed these
mutants into 5 phenotypic classes.
Class 1 mutants have narrow leaves, and veins are largely
replaced by a disorganized mass of tracheary elements (the
conducting cell type of xylem). Genes identified by this
mutant class are likely to play roles in specification of
organized veins.
In class 2 mutants, the linear secondary veins of wild type
are replaced by discontinuous vascular islands, suggesting
that the genes affected in these mutants function to
promote the linear pattern of veins (Deyholos et al., 2000).
Mutants in classes 3 and 4 have leaves with reduced
numbers of veins, suggesting that the genes identified by
these mutants function as positive regulators of vein
pattern. The two classes differ in the extent of defects:
class 3 mutants have defects restricted to leaves, whereas
in class 4 mutants, vein patterning defects extend to other
organs.
Class 5 mutants have leaves and cotyledons with too many
veins. This defect suggests that the genes identified by
these mutants might function as negative regulators of
vein patterning.
Currently, we are mapping each gene, ordering the genes
into complementation groups, identifying tagged alleles,
and cloning and characterizing the affected genes. We are
generating and characterizing double and triple mutants to
assemble the genes into developmental pathways, and
characterizing interactions with hormone signaling
pathways through analyses of hormone responses and
through genetic interactions of these mutants with
hormone response mutants.
Selected Publications
Deyholos, M.K., G. Cordner, D. Beebe and L.E. Sieburth. 2000.
The SCARFACE Gene is Required for Cotyledon and
Leaf Vein Patterning. Development (in press).
Sieburth, L.E. 1999. Auxin is required for leaf vein pattern
in Arabidopsis. Plant Physiology 121:1179-1190.
Sieburth, L.E., G.N. Drews and E.M. Meyerowitz. 1998. Non-
autonomy of AGAMOUS function in flower development: use
of a CRE/loxP method for mosaic analysis in
Arabidopsis. Development 125: 4303-4312
Sieburth, L.E. and E.M. Meyerowitz. 1997. Molecular
dissection of the AGAMOUS control region shows that cis
elements for spatial regulation are located intragenically.
Plant Cell 9:355-365
Jack, T., L.E. Sieburth and E.M. Meyerowitz. 1997. Targeted
Misexpression of AGAMOUS in Whorl 2 of
Arabidopsis Flowers. Plant Journal
11(4):825-839.
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