Daniel P Koenig, University of California Davis, California, USA
Neelima R Sinha, University of California Davis, California, USA
Published online: September 2007
DOI: 10.1002/9780470015902.a0020101
Development of a complex organ such as the leaf requires the coordinated action of numerous genetic factors. The advent of molecular genetics has allowed for the elucidation of many components of the genetic network controlling leaf development.
Keywords: leaf; polarity; KNOX; HDZIPIII; KANADI; YABBY; adaxial; abaxial
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Figure 1. Leaf developmental axes. (a) Leaves labelled with the three axes of leaf development. (b) Leaf of Zea mays. Red arrows mark the distal blade region and yellow arrows mark the proximal sheath. (c) Close up of Z. mays leaf highlighting the ligule tissue (arrow). (d) Leaf of Arabidopsis thaliana. Red and yellow arrows identify distal blade and proximal petiole regions, respectively. (e) Loss of adaxial identity in the tomato wiry6 mutant results in the production of bladeless or (f) cup-shaped leaves with reduced blade outgrowth.
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Figure 2. Genetic control of leaf development. (a) Diagram of the shoot apex showing genetic interactions separating shoot and leaf tissues as well as blade and petiole (meristem – orange, early leaf – yellow (left), blade yellow (right), and petiole – green). Genes listed in white font are repressed, while genes in black font are expressed in the designated tissue. (b) Diagram of cessation of cell division in leaves controlled by the TCP genes and JAGGED. JAG is not expressed in the leaf petiole. (c) Generalized model of regulation of the adaxial/abaxial axis. A cross-section through a leaf primordium is shown (adaxial – red, abaxial – purple). Arrow-heads designate the site of blade outgrowth resulting from the meeting of adaxial and abaxial identities.
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Figure 3. Modification of developmental pathways. (a) Diagramatic representation of the maize leaf (top) and the A. thaliana leaf (bottom), and the effect of prs and ns1ns2. The hypothesized upper and lower leaf zones are designated by the red and blue lines, respectively. (b) Wild-type tomato leaf. (c) The hypercompound leaf of the tomato Me mutant resulting from knox overexpression.
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Figure 4. Generalized model of genetic control of leaf shape. (a) False coloured scanning electron micrograph of a tomato apex. (purple – abaxial, red – adaxial, orange – meristem, yellow – distal, and green – proximal. The meeting of adaxial and abaxial identity is shown by the yellow dotted line and the medial lateral axis is designated by the double headed arrow). (b) Genetic interaction of genes controlling all axes of leaf development. Colour coding matches expression domain in the shoot in (a).
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| Further Reading | |
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