Floral Ontogeny of Aquilegia, Semiaquilegia, and Enemion (Ranunculaceae)

Tucker, Shirley C.; Hodges, Scott A.

doi:10.1086/429848

Cited by 87 publications

(111 citation statements)

References 31 publications

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“…Thus, minimal elaboration of an existing developmental mechanism can rapidly generate spur-length variation in the genus in concert with a specific ecological pressure, the presence of a pollinator with a dramatically longer tongue. Interestingly, there are taxa within the genera Semiaquilegia and Urophysa, which are very closely related to Aquilegia, that lack elongated spurs but produce small nectary cups or extremely short spurs [6,13,14], similar to very early developmental stages in Aquilegia. This implies that the evolutionary innovation underlying spur formation and the rapid radiation of Aquilegia may have been the mechanism of tuning cell anisotropy, which led to the elaboration of the nectary cup.…”

Section: Discussionmentioning

confidence: 99%

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Evolution of spur-length diversity in Aquilegia petals is achieved solely through cell-shape anisotropy

et al. 2011

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The role of petal spurs and specialized pollinator interactions has been studied since Darwin. Aquilegia petal spurs exhibit striking size and shape diversity, correlated with specialized pollinators ranging from bees to hawkmoths in a textbook example of adaptive radiation. Despite the evolutionary significance of spur length, remarkably little is known about Aquilegia spur morphogenesis and its evolution. Using experimental measurements, both at tissue and cellular levels, combined with numerical modelling, we have investigated the relative roles of cell divisions and cell shape in determining the morphology of the Aquilegia petal spur. Contrary to decades-old hypotheses implicating a discrete meristematic zone as the driver of spur growth, we find that Aquilegia petal spurs develop via anisotropic cell expansion. Furthermore, changes in cell anisotropy account for 99 per cent of the spur-length variation in the genus, suggesting that the true evolutionary innovation underlying the rapid radiation of Aquilegia was the mechanism of tuning cell shape.

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Section: Discussionmentioning

confidence: 99%

“…In this scenario, continued cell divisions combined with cell expansion is the primary driver of spur growth. Since Tepfer [5], the idea that spur growth occurs by essentially adding one cell at a time has been widely accepted [6,7], but has never been verified.…”

Section: Spur Development: Connecting Tissue Morphogenesis With Cell mentioning

confidence: 99%

Evolution of spur-length diversity in Aquilegia petals is achieved solely through cell-shape anisotropy

et al. 2011

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“…First, in the Nigella and Aquilegia ap3-3 mutants, petals were converted into sepals and thus the number of sepals increased (24). In the natural apetalous species, such as Thalictrum, Beesia, Enemion, and Clematis, however, the numbers of sepals did not increase, at least compared with their respective petalous relatives (36). This suggests that silencing of AP3-3 itself may not be sufficient for petal loss in natural apetalous species; other factors, such as shifts in the expression of C-function genes, may also be necessary.…”

Section: Ap3-3 Orthologs In Clematismentioning

confidence: 98%

Disruption of the petal identity gene APETALA3-3 is highly correlated with loss of petals within the buttercup family (Ranunculaceae)

Zhang

Guo

Zhang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Absence of petals, or being apetalous, is usually one of the most important features that characterizes a group of flowering plants at high taxonomic ranks (i.e., family and above). The apetalous condition, however, appears to be the result of parallel or convergent evolution with unknown genetic causes. Here we show that within the buttercup family (Ranunculaceae), apetalous genera in at least seven different lineages were all derived from petalous ancestors, indicative of parallel petal losses. We also show that independent petal losses within this family were strongly associated with decreased or eliminated expression of a single floral organ identity gene, APETALA3-3 ( AP3-3 ) , apparently owing to species-specific molecular lesions. In an apetalous mutant of Nigella , insertion of a transposable element into the second intron has led to silencing of the gene and transformation of petals into sepals. In several naturally occurring apetalous genera, such as Thalictrum , Beesia , and Enemion , the gene has either been lost altogether or disrupted by deletions in coding or regulatory regions. In Clematis , a large genus in which petalous species evolved secondarily from apetalous ones, the gene exhibits hallmarks of a pseudogene. These results suggest that, as a petal identity gene, AP3-3 has been silenced or down-regulated by different mechanisms in different evolutionary lineages. This also suggests that petal identity did not evolve many times independently across the Ranunculaceae but was lost in numerous instances. The genetic mechanisms underlying the independent petal losses, however, may be complex, with disruption of AP3-3 being either cause or effect.

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“…Flowers of Aquilegia are actinomorphic, pentamerous, and hypogynous with all floral parts unfused and arranged in whorls ( Figures 1A to 1C) (Munz, 1946;Tucker and Hodges, 2005). There are five organ types, from outermost to innermost: one whorl of 5 sepals, one whorl of 5 petals, four to seven whorls of 10 stamens, one whorl of 10 sterile staminodia, and one whorl of 5 free carpels.…”

Section: Wild-type Floral Morphology Of Aquilegia Vulgarismentioning

confidence: 99%

Elaboration of B Gene Function to Include the Identity of Novel Floral Organs in the Lower EudicotAquilegia

et al. 2007

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The basal eudicot Aquilegia (columbine) has an unusual floral structure that includes two morphologically distinct whorls of petaloid organs and a clearly differentiated fifth organ type, the staminodium. In this study, we have sought to determine how Aquilegia homologs of the B class genes APETALA3 (AP3) and PISTILLATA (PI) contribute to these novel forms of organ identity. Detailed expression analyses of the three AP3 paralogs and one PI homolog in wild-type and floral homeotic mutant lines reveal complex patterns that suggest that canonical B class function has been elaborated in Aquilegia. Yeast twohybrid studies demonstrate that the protein products of Aquilegia's AP3 and PI homologs can form heterodimers, much like what has been observed for their core eudicot homologs. Downregulation of AqvPI using virus-induced gene silencing indicates that in addition to petal and stamen identity, this locus is essential to staminodial identity but may not control the identity of the petaloid sepals. Our findings show that preexisting floral organ identity programs can be partitioned and modified to produce additional organ types. In addition, they indicate that some types of petaloid organs are not entirely dependent on AP3/PI homologs for their identity.

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Floral Ontogeny of Aquilegia, Semiaquilegia, and Enemion (Ranunculaceae)

Cited by 87 publications

References 31 publications

Evolution of spur-length diversity in Aquilegia petals is achieved solely through cell-shape anisotropy

Evolution of spur-length diversity in Aquilegia petals is achieved solely through cell-shape anisotropy

Disruption of the petal identity gene APETALA3-3 is highly correlated with loss of petals within the buttercup family (Ranunculaceae)

Elaboration of B Gene Function to Include the Identity of Novel Floral Organs in the Lower EudicotAquilegia

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