Next Article in Journal
The Hybridization Barrier between Herbaceous Medicago sativa and Woody M. arborea Is Weakened by Selection of Seed Parents
Next Article in Special Issue
Understanding of Leaf Development—the Science of Complexity
Previous Article in Journal
Extractions of High Quality RNA from the Seeds of Jerusalem Artichoke and Other Plant Species with High Levels of Starch and Lipid
Previous Article in Special Issue
Abaxial Greening Phenotype in Hybrid Aspen
Plants 2013, 2(2), 317-342; doi:10.3390/plants2020317

TALE and Shape: How to Make a Leaf Different

Istituto di Biologia e Biotecnologia Agraria, UOS Roma, Consiglio Nazionale delle Ricerche, Via Salaria Km. 29,300, Monterotondo Scalo, 00015 Roma, Italy
* Author to whom correspondence should be addressed.
Received: 18 February 2013 / Revised: 10 April 2013 / Accepted: 19 April 2013 / Published: 6 May 2013
(This article belongs to the Special Issue Leaf Development)
View Full-Text   |   Download PDF [774 KB, uploaded 6 May 2013]   |   Browse Figures


The Three Amino acid Loop Extension (TALE) proteins constitute an ancestral superclass of homeodomain transcription factors conserved in animals, plants and fungi. In plants they comprise two classes, KNOTTED1-LIKE homeobox (KNOX) and BEL1-like homeobox (BLH or BELL, hereafter referred to as BLH), which are involved in shoot apical meristem (SAM) function, as well as in the determination and morphological development of leaves, stems and inflorescences. Selective protein-protein interactions between KNOXs and BLHs affect heterodimer subcellular localization and target affinity. KNOXs exert their roles by maintaining a proper balance between undifferentiated and differentiated cell state through the modulation of multiple hormonal pathways. A pivotal function of KNOX in evolutionary diversification of leaf morphology has been assessed. In the SAM of both simple- and compound-leafed seed species, downregulation of most class 1 KNOX (KNOX1) genes marks the sites of leaf primordia initiation. However, KNOX1 expression is re-established during leaf primordia development of compound-leafed species to maintain transient indeterminacy and morphogenetic activity at the leaf margins. Despite the increasing knowledge available about KNOX1 protein function in plant development, a comprehensive view on their downstream effectors remains elusive. This review highlights the role of TALE proteins in leaf initiation and morphological plasticity with a focus on recent advances in the identification of downstream target genes and pathways.
Keywords: TALE; BLH; KNOX; homeobox transcription factors; target genes; leaf development; vascular development; cell fate; cell differentiation; shoot apical meristem TALE; BLH; KNOX; homeobox transcription factors; target genes; leaf development; vascular development; cell fate; cell differentiation; shoot apical meristem
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Share & Cite This Article

Further Mendeley | CiteULike
Export to BibTeX |
MDPI and ACS Style

Di Giacomo, E.; Iannelli, M.A.; Frugis, G. TALE and Shape: How to Make a Leaf Different. Plants 2013, 2, 317-342.

View more citation formats

Article Metrics


Cited By

[Return to top]
Plants EISSN 2223-7747 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert