First published online 14 July 2004
doi: 10.1242/dev.01262
Development 131, 3921-3929 (2004)
Published by The Company of Biologists 2004
The establishment of axial patterning in the maize leaf
Toshi Foster1,*,
,
Angela Hay2,*,
Robyn Johnston3 and
Sarah Hake4
1 The Horticulture and Food Research Institute of New Zealand, Private Bag 11
030, Palmerston North, New Zealand
2 Department of Plant Sciences, Oxford University, South Parks Road, Oxford, OX1
3RB, UK
3 Institute of Molecular BioSciences, Massey University, Private Bag 11 222,
Palmerston North, New Zealand
4 Plant Gene Expression Center, 800 Buchanan Street, Albany, CA 94710, USA
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Fig. 1. Leaf and whole plant phenotypes 8 weeks after planting. (A) Wild-type, (B)
Wab1, (C) lg1-R;Wab1 and (D) lg1-R plants. (E-H)
Adaxial view of blade-sheath boundary of (E) wild-type, (F) Wab1, (G)
lg1-R;Wab1, and (H) lg1-R leaves. a, auricle; b, blade; ae,
auricle extension; ea, ectopic auricle; es, ectopic sheath; lg, ligule; s,
sheath. Arrowhead in G indicate presumptive blade-sheath boundary in
lg1-R;Wab1 leaf.
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Fig. 2. Scanning electron and light micrographs illustrating epidermal and
histological features of wild-type and mutant leaves. (A-C) SEM of adaxial
surface of wild-type (A) blade, (B) auricle and (C) sheath. (D-G) Transverse
section through wild-type (D) blade, (E) auricle, (F) internal sheath and (G)
marginal sheath tissue. (H) Cartoon depicting regions where tissue was
sampled. (I-K) Transverse sections through (I) ectopic auricle in
Wab1 blade, (J) ectopic sheath in Wab1 blade and (K) ectopic
sheath in lg1-R;Wab1 blade. (L-M) SEM of adaxial surface of (L)
Wab1 ectopic auricle and (M) lg1-R;Wab1 ectopic sheath. All
sections are oriented with the adaxial surface upwards. Arrows in A and D
indicate multicellular base of macrohair. Normal bundle-sheath anatomy
indicated by arrowhead in D, abnormal bundle-sheath anatomy indicated by
arrowheads in I and J. Scale bars: 100 µm.
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Fig. 3. lg1 and lg2 expression in Wab1 leaves. RT-PCR
gel blot analysis of lg1 and lg2 expression in 4-week-old
seedlings of wild-type and Wab1/+ at the following stages of leaf
development: SAM including P1-5 (S), P6-8 pre-ligule region (PL), P6-8 blade
(B), P9-10 ligule region (L). Lanes 9-16 are as for lanes 1-8 using a
four-fold dilution of cDNA. Control with no cDNA included in PCR (C). Control
amplification of ubiquitin (ub) indicates equal amounts of
cDNA present in each sample.
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Fig. 4. Sector phenotypes in Wab1 mutants. (A-E) Abaxial view of
Wab1 leaves with auricle extension and/or ectopic auricle phenotypes
with albino sectors exhibiting normal blade characteristics. (F) Scanning
electron micrograph of adaxial surface of boxed region in C, illustrating
unexpanded, dovetailed auricle-like cells in Wab1/wab1+ ectopic
auricle tissue (right of arrowhead), and normal blade epidermal
characteristics such as macrohairs in the wab1+/– sector (left
of arrowhead). (G) Fluorescence micrograph of a transverse section through a
sector adjacent to auricle extension, illustrating a sharp boundary between
green, Wab1/wab1+ auricle-like tissue (which fluoresces red), and
albino, wab1+/– tissue (which appears blue-green). (H) SEM of
adaxial surface of sector boundary near that shown in G, with hairy, fully
expanded auricle-like cells in the Wab1/wab1+ tissue (right of
arrowhead) and normal blade cells including prickle hairs and macrohairs in
the wab1+/– tissue (left of arrowhead). (I) Fluorescence
micrograph of a transverse section through the sector shown in J. Green,
Wab1/wab1+ tissue is very thin with widely spaced veins, a hairless
adaxial surface and abaxial hairs characteristic of marginal sheath tissue.
Albino wab1+/– tissue has the histological organization of
normal blade tissue. (J) Abaxial view of sector adjacent to ectopic sheath
tissue, arrowhead marks sector boundary. (K) Cartoon depicting an albino
non-mutant (w3 wab1+/–) sector in a green Wab1/wab1+
leaf. Scale bar: 500 µm (F) and 100 µm (G-I).
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Fig. 5. Sector phenotypes in lg1-R;Wab1 mutants. (A) Abaxial view of
yellow v4, wab1+/– sector, and (B) adaxial and (C) abaxial view
of white, w3 wab1+/– sectors adjacent to ectopic sheath tissue.
Arrowheads in A and B mark sector borders. (E) Fluorescence micrograph of a
transverse section through the inner sector boundary of leaf shown in C. Green
lg1-R;Wab1 tissue has the histological organisation of sheath, and
albino wab1+/– tissue that of the blade. (D) SEM of adaxial
surface of sector boundary shown in C and D, illustrating the sharp boundary
between epidermal cell types in lg1-R;Wab1/wab1+ tissue (right of
arrowhead) and lg1-R;wab1+/– tissue (left of arrowhead). (F)
Fluorescence micrograph of a transverse section through another sector
adjacent to marginal sheath-like tissue. The adaxial surface of green
sheath-like tissue in D and F is hairless, whereas the albino tissue has hairs
specific to blade. Scale bar: 100 µm (D-F).
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Fig. 6. lg1 affects cell autonomy of the Wab1 phenotype. (A)
Cartoon illustrating spread of the Wab1 phenotype (wavy lines) into a
wab1+/– sector and spread of normal phenotype (no wavy lines)
from a sector into Wab1/wab1+ tissue. We propose that
lg1 may transmit both correct and incorrect positional signals
towards the margins of Wab1 leaves (red arrows). (B) In the absence
of lg1, the Wab1 phenotype is strictly cell-autonomous.
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Fig. 7. Model for lg1 function in leaf morphogenesis. (A) Cartoon of
wild-type leaf illustrating distal blade (green) and proximal sheath (blue)
separated by ligule and auricle (red). (B) In the absence of lg1,
ligule and auricle are deleted, the blade-sheath boundary is shifted distally,
and the base of the blade is narrower than in wild-type leaves. (C)
Wab1 disrupts proximodistal patterning and restricts lateral growth
of the blade. Misexpression of lg1 in Wab1 leaves results in
ectopic ligule and auricle, and partially compensates for the narrow leaf
phenotype at the base of the blade. The lateral signalling function of
lg1 permits some recovery of proximodistal patterning at the margins
of Wab1 leaves. (D) In the absence of lg1, Wab1 leaves never
establish blade at the margins and are extremely narrow.
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© The Company of Biologists Ltd 2004
