Towards an ontogenetic understanding of inflorescence diversity

Claßen‐Bockhoff, Regine; Bull–Hereñu, Kester

doi:10.1093/aob/mct009

Cited by 81 publications

(72 citation statements)

References 71 publications

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“…Pozner et al (2012) proposed that a major change during the evolution of the capitulum has been the suppression of the cymose patterning of these peripheral branches. Additionally, it has been proposed that the capitulum has evolved from a single, determinate, and expanding meristem that, through subdivision, gave rise to the multiflowered head (Claßen-Bockhoff and Bull-Hereñu, 2013).…”

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confidence: 99%

Co-opting floral meristem identity genes for patterning of the flower-like Asteraceae inflorescence

et al. 2016

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The evolutionary success of Asteraceae, the largest family of flowering plants, has been attributed to the unique inflorescence architecture of the family, which superficially resembles an individual flower. Here, we show that Asteraceae inflorescences (flower heads, or capitula) resemble solitary flowers not only morphologically but also at the molecular level. By conducting functional analyses for orthologs of the flower meristem identity genes LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) in Gerbera hybrida, we show that GhUFO is the master regulator of flower meristem identity, while GhLFY has evolved a novel, homeotic function during the evolution of head-like inflorescences. Resembling LFY expression in a single flower meristem, uniform expression of GhLFY in the inflorescence meristem defines the capitulum as a determinate structure that can assume floral fate upon ectopic GhUFO expression. We also show that GhLFY uniquely regulates the ontogeny of outer, expanded ray flowers but not inner, compact disc flowers, indicating that the distinction of different flower types in Asteraceae is connected with their independent evolutionary origins from separate branching systems.In flowering plants, inflorescences are the branched structures that bear flowers. Their architecture in terms of number and arrangement of flowers shows enormous variation in nature and plays a central role in angiosperm reproductive adaptation and success. Most of our knowledge of the molecular regulation of inflorescence architecture is based on studies of three major inflorescence types: racemes in Arabidopsis (Arabidopsis thaliana) or snapdragon (Antirrhinum majus), cymes in Solanaceae species such as petunia (Petunia hybrida) or tomato (Solanum lycopersicum), and panicles in grasses (Prusinkiewicz et al., 2007;Park et al., 2014;Teo et al., 2014). In the model plant Arabidopsis, endogenous and exogenous flowering-inducing signals convert the vegetative shoot meristem into an inflorescence meristem (IM) that initiates determinate flower meristems (FMs) on its flanks. The inflorescence forms a simple, indeterminate (monopodial) raceme that elongates and never forms a terminal flower due to maintenance of the stem cells in the central zone of the meristem. In Solanaceae, the cymous IM always terminates in a flower but forms new axillary IMs that continue growth, leading to a zig-zag-like sympodial branching pattern. Panicles in grasses show more complex lateral branching, and both apical and lateral meristems may form flowers. Using mathematical modeling, Prusinkiewicz et al. (2007) showed that a single developmental model (the so-called transient model) can generate the distinct inflorescence types (racemes, cymes, and panicles) found in nature.In all basic inflorescence types, flower meristem identity (FMI) is controlled by homologs of at least three functionally conserved proteins, LEAFY (LFY), UN-USUAL FLORAL ORGANS (UFO), and SEPALLATA3 (SEP3), that diverge in their spatiotemporal expression domains, leading to differences in IM patte...

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confidence: 99%

Co-opting floral meristem identity genes for patterning of the flower-like Asteraceae inflorescence

et al. 2016

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“…2) is the additional and very important characteristic of the plant growth power, permitting to speculate on a connection between the rosette diameter and SAM size (Claßen-Bockhoff and Bull-Herenu, 2013). In all Draba species listed in the previous sections, the diameter of rosettes of the generative shoots is significantly (p < 0.001) higher than that of the vegetative shoots (data not shown).…”

Section: Quantitative Traits For the Analysis Of Modular Structure Anmentioning

confidence: 81%

Intra-individual variation and evolution of modular structure in Draba plants

Grigorieva

Cherdantsev

2014

Biosystems

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“…Nevertheless, there are two possible explanations for the existence of proliferating inflorescences: either they actually rely on an inflorescence meristem that can be reverted to resume vegetative growth after flowering [39-43], or the supposed inflorescence is rather a vegetative shoot bearing lateral reproductive units, thus masking the appearance of a true inflorescence. This can be found in the same family, Myrtaceae (for example, Callistemon , Melaleuca [44], but also in other ones throughout the angiosperms ( Drimys winteri [45], Mahonia aquifolium , and Lysimachia nummularia [44]). Our observation of the sequential transformation of the inflorescence meristem in Actinodium definitively fits with the first interpretation.…”

Section: Discussionmentioning

confidence: 99%

The unique pseudanthium of Actinodium (Myrtaceae) - morphological reinvestigation and possible regulation by CYCLOIDEA-like genes

Claßen‐Bockhoff

Ruonala

Bull–Hereñu

et al. 2013

EvoDevo

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BackgroundGenes encoding TCP transcription factors, such as CYCLOIDEA-like (CYC-like) genes, are well known actors in the control of plant morphological development, particularly regarding the control of floral symmetry. Despite recent understanding that these genes play a role in establishing the architecture of inflorescences in the sunflower family (Asteraceae), where hundreds of finely organized flowers are arranged to mimic an individual flower, little is known about their function in the development of flower-like inflorescences across diverse phylogenetic groups. Here, we studied the head-like pseudanthium of the Australian swamp daisy Actinodium cunninghamii Schau. (Myrtaceae, the myrtle family), which consists of a cluster of fertile flowers surrounded by showy ray-shaped structures, to fully characterize its inflorescence development and to test whether CYC-like genes may participate in the control of its daisy-like flowering structures.ResultsWe used standard morphological and anatomical methods to analyze Actinodium inflorescence development. Furthermore, we isolated Actinodium CYC-like genes using degenerate PCR primers, and studied the expression patterns of these genes using quantitative RT-PCR. We found that the ray-shaped elements of Actinodium are not single flowers but instead branched short-shoots occasionally bearing flowers. We found differential expression of CYC-like genes across the pseudanthium of Actinodium, correlating with the showiness and branching pattern of the ray structures.ConclusionsThe Actinodium inflorescence represents a novel type of pseudanthium with proximal branches mimicking ray flowers. Expression patterns of CYC-like genes are suggestive of participation in the control of pseudanthium development, in a manner analogous to the distantly related Asteraceae. As such, flowering plants appear to have recruited CYC-like genes for heteromorphic inflorescence development at least twice during their evolutionary history.

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Towards an ontogenetic understanding of inflorescence diversity

Cited by 81 publications

References 71 publications

Co-opting floral meristem identity genes for patterning of the flower-like Asteraceae inflorescence

Co-opting floral meristem identity genes for patterning of the flower-like Asteraceae inflorescence

Intra-individual variation and evolution of modular structure in Draba plants

The unique pseudanthium of Actinodium (Myrtaceae) - morphological reinvestigation and possible regulation by CYCLOIDEA-like genes

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