The ABC Model and its Applicability to Basal Angiosperms

Soltis, Douglas E.; Chanderbali, André S.; Kim, Sangtae; Buzgo, Matyas; Soltis, Pamela S.

doi:10.1093/aob/mcm117

Cited by 145 publications

(109 citation statements)

References 51 publications

(65 reference statements)

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“…In a broader comparative framework, although the domain of expression of AP3 and PI orthologs varied over the evolution of flowering plants, it is important to note that the BC combinatory function has consistently remained restricted to the third whorl, where stamens develop in hermaphroditic flowers ( Figure 6; Xiao et al, 2003;Irish and Litt, 2005;Kim et al, 2005;Soltis et al, 2007;Theissen and Melzer, 2007;Whipple et al, 2007;Mondragó n-Palomino and Theissen, 2009;Á lvarez-Buylla et al, 2010b). Furthermore, to the best of our knowledge, in no other case, including the one presented here, has the BC combinatory function been displaced to the flower center in bisexual flowers, resulting in central stamen development (Figure 6 and references therein).…”

Section: Discussionmentioning

confidence: 99%

B-Function Expression in the Flower Center Underlies the Homeotic Phenotype ofLacandonia schismatica(Triuridaceae)

et al. 2010

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Spontaneous homeotic transformations have been described in natural populations of both plants and animals, but little is known about the molecular-genetic mechanisms underlying these processes in plants. In the ABC model of floral organ identity in Arabidopsis thaliana, the B-and C-functions are necessary for stamen morphogenesis, and C alone is required for carpel identity. We provide ABC model-based molecular-genetic evidence that explains the unique inside-out homeotic floral organ arrangement of the monocotyledonous mycoheterotroph species Lacandonia schismatica (Triuridaceae) from Mexico. Whereas a quarter million flowering plant species bear central carpels surrounded by stamens, L. schismatica stamens occur in the center of the flower and are surrounded by carpels. The simplest explanation for this is that the B-function is displaced toward the flower center. Our analyses of the spatio-temporal pattern of B-and C-function gene expression are consistent with this hypothesis. The hypothesis is further supported by conservation between the B-function genes of L. schismatica and Arabidopsis, as the former are able to rescue stamens in Arabidopsis transgenic complementation lines, and Ls-AP3 and Ls-PI are able to interact with each other and with the corresponding Arabidopsis B-function proteins in yeast. Thus, relatively simple molecular modifications may underlie important morphological shifts in natural populations of extant plant taxa. INTRODUCTION An ABC Model-Based Hypothesis of the Developmental Genetic Factors Underlying the Unusual Reproductive Morphology of Lacandonia schismaticaThe ABC model for the specification of floral organ identity Coen and Meyerowitz, 1991;Meyerowitz et al., 1991) has played a critical role in the modern explanation of the molecular-genetic determinants of the ontogenetic development of reproductive structures in angiosperms. This combinatorial genetic model has guided diverse plant evolutionary developmental biology studies, especially during the formative years of this young field (Cronk, 2001;Cronk et al., 2002;Pruitt et al., 2003). As part of the larger discipline of evo-devo, the articulation of explanatory tools like the ABC model is considered essential for understanding the developmental mechanisms that underlie morphological innovation throughout evolutionary time (Cronk et al., 2002;Carroll et al., 2004;Gilbert, 2006;Wolpert et al., 2006).The ABC model of flower development was based on the interpretation of floral homeotic phenotypes in Arabidopsis thaliana and Antirrhinum majus (Coen and Meyerowitz, 1991). However, the participation of homeotic transformations and other forms of heterotopy in the appearance of new organ arrangements during the evolution of angiosperms had already been considered in the botanical literature, long before the age of plant developmental genetics (e.g., Meyer, 1966;Sattler, 1984;Bowman et al., 1989;Weston, 2000). Outstanding instances of spontaneous floral homeotic phenotypes have continued to be recorded in well-characterized taxa (s...

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Section: Discussionmentioning

confidence: 99%

B-Function Expression in the Flower Center Underlies the Homeotic Phenotype ofLacandonia schismatica(Triuridaceae)

et al. 2010

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“…2B and 3A; Kanno et al, 2003). This model was extended further as the modified ABCE model after discovering the Class E function genes (Krizek and Fletcher, 2005;Soltis et al, 2007).…”

Section: Molecular Mechanisms Determining Floral Architecture In Dicomentioning

confidence: 99%

Molecular Mechanism Regulating Floral Architecture in Monocotyledonous Ornamental Plants

Kanno

2016

The Hortic J

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Molecular and genetic analyses of flower development have been conducted primarily in dicot model plants such as Arabidopsis thaliana and Antirrhinum majus. The obtained data are the basis for the ABC model, which was extended to the ABCE model of floral development. This model has been validated in many dicot species using genetic transformation studies and mutant analyses. Many dicot flowers have two distinctive perianth whorls, which include greenish sepals and showy petals. By contrast, the monocot lily flower has two almost identical petaloid whorls, the inner and outer tepals. To explain this type of floral morphology, a modified ABC model, the further extended modified ABCE model, was proposed. According to this model, B-class genes are expressed in whorls 1-3, and whorls 1 and 2 form petaloid structures. This review describes the molecular mechanisms regulating flower development in monocots. Since the showy perianth is one of the most important traits in floricultural crops, we focused on the B-and C-class genes, which are related to the development and modification of the perianth. The review describes the expression patterns of floral organ identity genes, and presents functional studies using double-flowered and viridiflora cultivars in some monocot species. Besides lily-type flowers, there are several types of monocot flower, such as commelina type with two whorls of distinctive perianth, orchid and grass flowers. The review also describes the molecular analyses of these types of monocot flower.

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“…A ''fading border'' model has been proposed to explain this pattern at the genetic level (Buzgo et al 2004;Soltis et al 2007aSoltis et al , 2007b). It appears easier to apply this model to describe the development of flowers with an increased (evolutionarily derived) number of perianth organs in spiral arrangement rather than to see it as an expression of a primitively multistep gradation from an outer to an inner morph of tepals or from sepals to petals.…”

Section: Bracts and Tepals Sepaloid And Petaloid Tepals And Sepalsmentioning

confidence: 99%

“…As a further step, the evolution of the diversity of these features should be analyzed on the basis of the currently available phylogenetic studies of angiosperms; there are some initial attempts of such studies (Doyle and Endress 2000;Ronse De Craene et al 2003;Zanis et al 2003;Doyle 2007, 2008). Likewise, the genetic program for perianth development and its origin and evolution in angiosperms should also be further elucidated Stellari et al 2004;Kim et al 2005;Baum and Hileman 2006;Irish 2006;Kramer and Zimmer 2006;Soltis et al , 2007aSoltis et al , 2007bLitt 2007). Both the structural and the developmental genetic approach would be important to evaluate homologies (Wagner 2007).…”

Section: Perianth Organ Origin and Evolutionary Differentiationmentioning

confidence: 99%

Perianth Biology in the Basal Grade of Extant Angiosperms

Endress

2008

International Journal of Plant Sciences

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Perianth structure and behavior were studied comparatively in representatives of all families of the basalmost extant angiosperms (ANITA grade plus Chloranthaceae). In addition, data from the literature were reviewed. Tepal aestivation is spiral imbricate in Amborella and Austrobaileyales, with broadly overlapping flanks; aestivation is mainly contort within each of the two tepal whorls in Cabomba (but open within each whorl and imbricate only between whorls in Brasenia) and is whorled imbricate in Nymphaeaceae. Tepals are absent in Hydatellaceae, Chloranthaceae (other than Hedyosmum), and Ceratophyllaceae. In two genera of Nymphaeales (Cabomba and Nuphar), nectaries are present on inner tepals. Tepals are caducous during or at the end of anthesis in Austrobaileyales. Preformations of the tepal abscission zone in flowers with caducous tepals include a narrow tepal base, constriction as seen in median longitudinal sections, and small-celled tissue. In contrast, the perianth organs of Amborella, Nymphaeales, and Chloranthaceae are not caducous and are associated with a broad tepal base without indentation and often without small-celled tissue. Only in the latter groups are there genera with basally united tepals (Amborella, Cabomba, and Hedyosmum). Perianth structure and behavior were studied comparatively in representatives of all families of the basalmost extant angiosperms (ANITA grade plus Chloranthaceae). In addition, data from the literature were reviewed. Tepal aestivation is spiral imbricate in Amborella and Austrobaileyales, with broadly overlapping flanks; aestivation is mainly contort within each of the two tepal whorls in Cabomba (but open within each whorl and imbricate only between whorls in Brasenia) and is whorled imbricate in Nymphaeaceae. Tepals are absent in Hydatellaceae, Chloranthaceae (other than Hedyosmum), and Ceratophyllaceae. In two genera of Nymphaeales (Cabomba and Nuphar), nectaries are present on inner tepals. Tepals are caducous during or at the end of anthesis in Austrobaileyales. Preformations of the tepal abscission zone in flowers with caducous tepals include a narrow tepal base, constriction as seen in median longitudinal sections, and small-celled tissue. In contrast, the perianth organs of Amborella, Nymphaeales, and Chloranthaceae are not caducous and are associated with a broad tepal base without indentation and often without small-celled tissue. Only in the latter groups are there genera with basally united tepals (Amborella, Cabomba, and Hedyosmum). PERIANTH BIOLOGY IN THE BASAL GRADE OF EXTANT ANGIOSPERMS

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The ABC Model and its Applicability to Basal Angiosperms

Cited by 145 publications

References 51 publications

B-Function Expression in the Flower Center Underlies the Homeotic Phenotype ofLacandonia schismatica(Triuridaceae)

B-Function Expression in the Flower Center Underlies the Homeotic Phenotype ofLacandonia schismatica(Triuridaceae)

Molecular Mechanism Regulating Floral Architecture in Monocotyledonous Ornamental Plants

Perianth Biology in the Basal Grade of Extant Angiosperms

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