Signals and prepatterns: new insights into organ polarity in plants

Husbands, Aman Y.; Chitwood, Daniel H.; Plavskin, Yevgeniy; Timmermans, Marja C.P.

doi:10.1101/gad.1819909

Cited by 188 publications

(154 citation statements)

References 84 publications

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“…In addition, AS1-AS2 reinforces adaxial identity at the cellular level through direct, Polycomb-mediated repression of the abaxial determinant YAB5. However, as YABBY genes display considerable variability in expression patterns across species (Husbands et al, 2009), the regulatory relationships between them and orthologous AS1-AS2 complexes remain an open and intriguing question. Taken together, our data reveal how the versatile regulatory properties of AS1-AS2 impact the robust placement of the adaxial-abaxial boundary, contributing to the production of a flat leaf.…”

Section: Further Roles For As1-as2 In Adaxial-abaxial Patterningmentioning

confidence: 99%

“…Formation of the flat leaf thus poses an interesting mechanistic challenge, namely, how to create a stable boundary throughout the plane of a long and wide, yet shallow, structure. The clean separation of adaxial and abaxial fates, at both the cell and the domain level, relies on positive and negative feedback regulation between polarity determinants that reinforce initial cell fate decisions (Husbands et al, 2009). However, few of these regulatory interactions are understood at the mechanistic level.…”

Section: As1-as2 Uses Distinct Mechanisms To Regulate Its Polarity Tamentioning

confidence: 99%

“…The acquisition and maintenance of adaxial-abaxial polarity are driven by a complex, redundant gene regulatory network with several highly conserved transcription factor families that promote either adaxial or abaxial fate at its core (reviewed in Husbands et al, 2009;Moon and Hake, 2011). Members of the CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIPIII) family, which in Arabidopsis thaliana includes PHABULOSA (PHB), PHAVOLUTA, and REVOLUTA (REV), specify adaxial cell fate (McConnell et al, 2001;Emery et al, 2003;Juarez et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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The ASYMMETRIC LEAVES Complex Employs Multiple Modes of Regulation to Affect Adaxial-Abaxial Patterning and Leaf Complexity

et al. 2015

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Flattened leaf architecture is not a default state but depends on positional information to precisely coordinate patterns of cell division in the growing primordium. This information is provided, in part, by the boundary between the adaxial (top) and abaxial (bottom) domains of the leaf, which are specified via an intricate gene regulatory network whose precise circuitry remains poorly defined. Here, we examined the contribution of the ASYMMETRIC LEAVES (AS) pathway to adaxial-abaxial patterning in Arabidopsis thaliana and demonstrate that AS1-AS2 affects this process via multiple, distinct regulatory mechanisms. AS1-AS2 uses Polycomb-dependent and -independent mechanisms to directly repress the abaxial determinants MIR166A, YABBY5, and AUXIN RESPONSE FACTOR3 (ARF3), as well as a nonrepressive mechanism in the regulation of the adaxial determinant TAS3A. These regulatory interactions, together with data from prior studies, lead to a model in which the sequential polarization of determinants, including AS1-AS2, explains the establishment and maintenance of adaxial-abaxial leaf polarity. Moreover, our analyses show that the shared repression of ARF3 by the AS and trans-acting small interfering RNA (ta-siRNA) pathways intersects with additional AS1-AS2 targets to affect multiple nodes in leaf development, impacting polarity as well as leaf complexity. These data illustrate the surprisingly multifaceted contribution of AS1-AS2 to leaf development showing that, in conjunction with the ta-siRNA pathway, AS1-AS2 keeps the Arabidopsis leaf both flat and simple.

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Section: Further Roles For As1-as2 In Adaxial-abaxial Patterningmentioning

confidence: 99%

Section: As1-as2 Uses Distinct Mechanisms To Regulate Its Polarity Tamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The ASYMMETRIC LEAVES Complex Employs Multiple Modes of Regulation to Affect Adaxial-Abaxial Patterning and Leaf Complexity

et al. 2015

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“…Identification of genes responsible for unifacial leaf development is essential for a better understanding of the developmental and evolutionary mechanisms underlying unifacial leaf blade formation. The establishment of adaxial-abaxial polarity is regulated by several distinct families of transcription factors and small regulatory RNAs (Husbands et al, 2009). It is possible that a genetic change or changes in one or more of these regulators may have resulted in unifacial leaf development.…”

Section: Unifacial Leaf Blades Are Abaxialized At the Gene Expressionmentioning

confidence: 99%

“…The adaxial domain of a leaf primordium is adjacent to the SAM and differentiates into the upper side of the leaf, whereas the abaxial domain is away from the SAM and differentiates into the lower side of the leaf (Steeves and Sussex, 1989). The establishment of adaxial-abaxial polarity in bifacial leaves is regulated by overlapping and antagonistic genetic interactions involving several distinct transcription factors and small regulatory RNAs (Husbands et al, 2009). In both eudicots and monocots, these include members of the Class III Homeodomain Leucine Zipper (HD-ZIPIII) gene family (McConnell et al, 2001;Juarez et al, 2004;Itoh et al, 2008b), which specify adaxial identity and are expressed in the adaxial domain of leaves, and KANADI Kerstetter et al, 2001;Candela et al, 2008;Zhang et al, 2009) and AUXIN RESPONSE FACTOR3 (ARF3)/ETTIN (ETT) genes (Pekker et al, 2005;Itoh et al, 2008a), which are expressed abaxially, where they specify abaxial identity.…”

Section: Introductionmentioning

confidence: 99%

Genetic Framework for Flattened Leaf Blade Formation in Unifacial Leaves ofJuncus prismatocarpus

2010

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Angiosperm leaves generally develop as bifacial structures with distinct adaxial and abaxial identities. However, several monocot species, such as iris and leek, develop unifacial leaves, in which leaf blades have only abaxial identity. In bifacial leaves, adaxial-abaxial polarity is required for leaf blade flattening, whereas many unifacial leaves become flattened despite their leaf blades being abaxialized. Here, we investigate the mechanisms underlying the development and evolution of flattened leaf blades in unifacial leaves. We demonstrate that the unifacial leaf blade is abaxialized at the gene expression level and that an ortholog of the DROOPING LEAF (DL) gene may promote flattening of the unifacial leaf blade. In two closely related Juncus species, Juncus prismatocarpus, which has flattened unifacial leaves, and Juncus wallichianus, which has cylindrical unifacial leaves, DL expression levels and patterns correlate with the degree of laminar outgrowth. Genetic and expression studies using interspecific hybrids of the two species reveal that the DL locus from J. prismatocarpus flattens the unifacial leaf blade and expresses higher amounts of DL transcript than does that from J. wallichianus. We also show that leaf blade flattening is a trigger for central-marginal leaf polarity differentiation. We suggest that flattened unifacial leaf blades may have evolved via the recruitment of DL function, which plays a similar cellular but distinct phenotypic role in monocot bifacial leaves.

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Genetic Control of Leaf Shape

Martinez

Sinha

2013

Encyclopedia of Life Sciences

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The variability in leaf morphology is vast; therefore, an understanding of how leaves achieve this diversity has captured the attention of many developmental biologists. Genetic mechanisms that regulate leaf shape are repeated throughout both development and between species. Leaves initiate off the shoot apical meristem and development proceeds from cell division to cell elongation. Leaf initiation and the establishment of the three main axes of a leaf are largely directed by the plant hormone auxin. Work across species reveals that adjustments to the repeated interaction of auxin, gene expression changes and small ribonucleic acid (RNA) regulation allowed species‐specific leaf shape differences to emerge. Further, genetic interactions leading to patterning in simple leaf development are reiterated during establishment of leaf complexity. To understand leaf development in an evolutionary context, future research must take advantage of the ever‐expanding genomic tools in nonmodel organisms that exhibit leaf shape diversity. Key Concepts: Leaves originate from clusters of stem cells called meristems. The development of leaves occurs along three main axes: (1) adaxial/abaxial, (2) proximal/distal and (3) medial/lateral. The development of both meristems and leaves involve morphogenetic activity in zones which are defined by distinct gene expression and cell division/elongation patterns. The transport and concentration of the hormone auxin largely directs many aspects of leaf morphogenesis. Leaf and leaflet initiation first begin with the formation of auxin maxima. Recycling of genetic mechanisms is a theme that occurs throughout leaf development.

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Signals and prepatterns: new insights into organ polarity in plants

Cited by 188 publications

References 84 publications

The ASYMMETRIC LEAVES Complex Employs Multiple Modes of Regulation to Affect Adaxial-Abaxial Patterning and Leaf Complexity

The ASYMMETRIC LEAVES Complex Employs Multiple Modes of Regulation to Affect Adaxial-Abaxial Patterning and Leaf Complexity

Genetic Framework for Flattened Leaf Blade Formation in Unifacial Leaves ofJuncus prismatocarpus

Genetic Control of Leaf Shape

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