Dataset Information

Sepal Identity of the Pappus and Floral Organ Development in the Common Dandelion (Taraxacum officinale; Asteraceae).

ABSTRACT: The dry one-seeded fruits (cypselae) of the Asteraceae are often crowned with a pappus, an appendage of hairs or scales that assists in dispersal. It is generally assumed, but little investigated, that the pappus represents the outer floral whorl where the sepals are usually located. We analysed pappus-sepal homology in dandelions using micromorphological and floral gene expression analyses. We show that the pappus initiates from a ring primordium at the base of the corolla, heterochronic to the petals. Pappus parts form from this ring, with those in the alternipetalaous position usually being ahead in growth, referring to sepal identity. Tof-APETALLA1 expression increased during floret development and was highest in mature pappus. Tof-PISTILLATA expression was high and confined to the floral tissues containing the petals and stamens, consistent with expectations for sepals. Apart from the pappus, the dispersal structure of dandelion consists of the upper part of the fruit, the beak, which originates from the inner floral whorl. Thus, our results support the homology of the pappus with the sepals, but show that it is highly derived. Together with our floral stage definitions and verified qPCR reference genes, they provide a basis for evolution and development studies in dandelions and possibly other Asteraceae.

SUBMITTER: Vijverberg K

PROVIDER: S-EPMC8398263 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Publications

Sepal Identity of the Pappus and Floral Organ Development in the Common Dandelion (Taraxacum officinale; Asteraceae).

Vijverberg Kitty K Welten Monique M Kraaij Marjan M van Heuven Bertie Joan BJ Smets Erik E Gravendeel Barbara B

Plants (Basel, Switzerland) 20210816 8

The dry one-seeded fruits (cypselae) of the Asteraceae are often crowned with a pappus, an appendage of hairs or scales that assists in dispersal. It is generally assumed, but little investigated, that the pappus represents the outer floral whorl where the sepals are usually located. We analysed pappus-sepal homology in dandelions using micromorphological and floral gene expression analyses. We show that the pappus initiates from a ring primordium at the base of the corolla, ...[more]

PMID: 34451727

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Project description:The study aims to achieve several objectives: determine background element concentrations in Taraxacum officinale F.H. Wigg-common dandelion roots, stems, and flowers; clarify T. officinale's ability to accumulate trace elements (TEs) in plant parts; calculate accumulation and translocation factors to identify hyperaccumulator potential; and contribute to practical applications in geochemical prospecting, exploration geochemistry, phytomining, and environmental remediation. To accomplish this, 34 samples of T. officinale and associated soil samples were gathered from the plant's habitat along the roadside for trace element (TE) analysis. The elemental composition of both plants and soils underwent analysis using diverse statistical approaches, including factor analysis, ANOVA tests, and descriptive parameters. Plant element accumulation patterns and tendencies across various plant parts were explored through bioconcentration (BCFs) and translocation factors (TFs). Results showed that T. officinale accumulates some TEs in its roots, stems, and flowers, with the highest concentrations found in the roots. The factor analysis of plant element contents indicated a grouping tendency among elements. Specifically, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn exhibited a tendency to co-occur, while Ba, Mo, and Sr formed a separate group. Furthermore, in the flowers of the plant, Al, Ba, Co, Cr, Fe, Mn, Ni, and Sr showed a similar grouping, while Cu, Pb, and Zn formed a distinct cluster. ANOVA tests demonstrated significant variations in the accumulation of Al, Ba, Cr, Fe, and Sr among the roots, flowers, and stems of the plant. Additionally, Ni and Pb exhibited noteworthy differences in accumulation between these plant parts. Furthermore, Mn and Zn showed significant discrepancies in their accumulation capacities across all parts of the plant. T. officinale was identified as a lead hyperaccumulator by the study, with BCFs and concentrations exceeding 1000 mg kg-1. These findings inform strategies for phytoremediation and enhance our understanding of the plant's potential role in exploration studies and environmental management in metal-rich regions.

Project description:Chloroplast DNA sequences show substantial variation between higher plant species, and less variation within species, so are typically excellent markers to investigate evolutionary, population and genetic relationships and phylogenies. We sequenced the plastomes of Taraxacum obtusifrons Markl. (O978); T. stridulum Trávniček ined. (S3); and T. amplum Markl. (A978), three apomictic triploid (2n = 3x = 24) dandelions from the T. officinale agg. We aimed to characterize the variation in plastomes, define relationships and correlations with the apomictic microspecies status, and refine placement of the microspecies in the evolutionary or phylogenetic context of the Asteraceae. The chloroplast genomes of accessions O978 and S3 were identical and 151,322 bp long (where the nuclear genes are known to show variation), while A978 was 151,349 bp long. All three genomes contained 135 unique genes, with an additional copy of the trnF-GGA gene in the LSC region and 20 duplicated genes in the IR region, along with short repeats, the typical major Inverted Repeats (IR1 and IR2, 24,431bp long), and Large and Small Single Copy regions (LSC 83,889bp and SSC 18,571bp in O978). Between the two Taraxacum plastomes types, we identified 28 SNPs. The distribution of polymorphisms suggests some parts of the Taraxacum plastome are evolving at a slower rate. There was a hemi-nested inversion in the LSC region that is common to Asteraceae, and an SSC inversion from ndhF to rps15 found only in some Asteraceae lineages. A comparative repeat analysis showed variation between Taraxacum and the phylogenetically close genus Lactuca, with many more direct repeats of 40bp or more in Lactuca (1% larger plastome than Taraxacum). When individual genes and non-coding regions were for Asteraceae phylogeny reconstruction, not all showed the same evolutionary scenario suggesting care is needed for interpretation of relationships if a limited number of markers are used. Studying genotypic diversity in plastomes is important to characterize the nature of evolutionary processes in nuclear and cytoplasmic genomes with the different selection pressures, population structures and breeding systems.

Dataset Information

Sepal Identity of the Pappus and Floral Organ Development in the Common Dandelion (Taraxacum officinale; Asteraceae).

Publications

Sepal Identity of the Pappus and Floral Organ Development in the Common Dandelion (<i>Taraxacum officinale</i>; Asteraceae).

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