Phyllotactic patterning of gerbera flower heads Zhang, Teng; Cieslak, Mikolaj; Owens, Andrew ...
Proceedings of the National Academy of Sciences - PNAS,
03/2021, Letnik:
118, Številka:
13
Journal Article
Recenzirano
Odprti dostop
Phyllotaxis, the distribution of organs such as leaves and flowers on their support, is a key attribute of plant architecture. The geometric regularity of phyllotaxis has attracted multidisciplinary ...interest for centuries, resulting in an understanding of the patterns in the model plants
and tomato down to the molecular level. Nevertheless, the iconic example of phyllotaxis, the arrangement of individual florets into spirals in the heads of the daisy family of plants (Asteraceae), has not been fully explained. We integrate experimental data and computational models to explain phyllotaxis in
We show that phyllotactic patterning in gerbera is governed by changes in the size of the morphogenetically active zone coordinated with the growth of the head. The dynamics of these changes divides the patterning process into three phases: the development of an approximately circular pattern with a Fibonacci number of primordia near the head rim, its gradual transition to a zigzag pattern, and the development of a spiral pattern that fills the head on the template of this zigzag pattern. Fibonacci spiral numbers arise due to the intercalary insertion and lateral displacement of incipient primordia in the first phase. Our results demonstrate the essential role of the growth and active zone dynamics in the patterning of flower heads.
The large sunflower family, Asteraceae, is characterized by compressed, flower-like inflorescences that may bear phenotypically distinct flower types. The CYCLOIDEA (CYC)/TEOSINTE BRANCHED1-like ...transcription factors (TFs) belonging to the TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) protein family are known to regulate bilateral symmetry in single flowers. In Asteraceae, they function at the inflorescence level, and were recruited to define differential flower type identities. Here, we identified upstream regulators of
, a gene that specifies ray flower identity at the flower head margin in the model plant
We discovered a previously unidentified expression domain and functional role for the paralogous CINCINNATA-like TCP proteins. They function upstream of
and affect the developmental delay of marginal ray primordia during their early ontogeny. At the level of single flowers, the Asteraceae
genes show a unique function in regulating the elongation of showy ventral ligules that play a major role in pollinator attraction. We discovered that during ligule development, the E class MADS-box TF GRCD5 activates
expression. We propose that the C class MADS-box TF GAGA1 contributes to stamen development upstream of
Our data demonstrate how interactions among and between the conserved floral regulators, TCP and MADS-box TFs, contribute to the evolution of the elaborate inflorescence architecture of Asteraceae.
Poison hemlock (Conium maculatum L.) is a notorious weed containing the potent alkaloid coniine. Only some of the enzymes in the coniine biosynthesis have so far been characterized. Here, we utilize ...the next-generation RNA sequencing approach to report the first-ever transcriptome sequencing of five organs of poison hemlock: developing fruit, flower, root, leaf, and stem. Using a de novo assembly approach, we derived a transcriptome assembly containing 123,240 transcripts. The assembly is deemed high quality, representing over 88% of the near-universal ortholog genes of the Eudicots clade. Nearly 80% of the transcripts were functionally annotated using a combination of three approaches. The current study focuses on describing the coniine pathway by identifying in silico transcript candidates for polyketide reductase, L-alanine:5-keto-octanal aminotransferase, γ-coniceine reductase, and S-adenosyl-L-methionine:coniine methyltransferase. In vitro testing will be needed to confirm the assigned functions of the selected candidates.
Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an ...attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightly-linked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipitation for PHYC. Similar associations characterized the growth-promoting cytokinin response regulator ARR1, and the wood development genes KAK and MED5A.
Genetic engineering of petunia was shown to lead to novel flower color some 20 years ago. Here we show that petunia lines with orange flowers, generated for scientific purposes, apparently found ...their way to petunia breeding programmes, intentionally or unintentionally. Today they are widely available, but have not been registered for commerce.
Summary
Plant polyketides are well‐known for their crucial functions in plants and their importance in the context of human health. They are synthesized by type III polyketide synthases (PKSs) and ...their final functional diversity is determined by post‐PKS tailoring enzymes. Gerbera hybrida is rich in two defense‐related polyketides: gerberin and parasorboside. Their synthesis is known to be initiated by GERBERA 2‐PYRONE SYNTHASE 1 (G2PS1), but the polyketide reductases (PKRs) that determine their final structure have not yet been identified.
We identified two PKR candidates in the pathway, GERBERA REDUCTASE 1 (GRED1) and GRED2. Gene expression and metabolite analysis of different gerbera tissues, cultivars, and transgenic gerbera plants, and in vitro enzyme assays, were performed for functional characterization of the enzymes.
GRED1 and GRED2 catalyze the second reduction step in parasorboside biosynthesis. They reduce the proximal keto domain of the linear CoA bound intermediate before lactonization.
We identified a crucial tailoring step in an important gerbera PKS pathway and show that plant polyketide biosynthesis shares processing strategies with fungi and bacteria. The two tailoring enzymes are recruited from the ancient sporopollenin biosynthetic pathway to a defense‐related PKS pathway in gerbera. Our data provide an example of how plants recruit conserved genes to new functions in secondary metabolism that are important for environmental adaptation.
The pseudanthial inflorescences of the sunflower family, Asteraceae, mimic a solitary flower but are composed of multiple flowers. Our studies in Gerbera hybrida indicate functional diversification ...for SEPALLATA (SEP)-like MADS box genes that often function redundantly in other core eudicots.
We conducted phylogenetic and expression analysis for eight SEP-like GERBERA REGULATOR OF CAPITULUM DEVELOPMENT (GRCD) genes, including previously unstudied gene family members. Transgenic gerbera plants were used to infer gene functions.
Adding to the previously identified stamen and carpel functions for GRCD1 and GRCD2, two partially redundant genes, GRCD4 and GRCD5, were found to be indispensable for petal development. Stepwise conversion of floral organs into leaves in the most severe RNA interference lines suggest redundant and additive GRCD activities in organ identity regulation. We show conserved and redundant functions for several GRCD genes in regulation of flower meristem maintenance, while functional diversification for three SEP1/2/4 clade genes in regulation of inflorescence meristem patterning was observed.
GRCD genes show both specialized and pleiotropic functions contributing to organ differentiation and flower meristem fate, and uniquely, to patterning of the inflorescence meristem. Altogether, we provide an example of how plant reproductive evolution has used conserved genetic modules for regulating the elaborate inflorescence architecture in Asteraceae.
Apoplastic events such as monolignol oxidation and lignin polymerization are difficult to study in intact trees. To investigate the role of apoplastic hydrogen peroxide (H₂O₂) in gymnosperm phenolic ...metabolism, an extracellular lignin-forming cell culture of Norway spruce (Picea abies) was used as a research model. Scavenging of apoplastic H₂O₂ by potassium iodide repressed lignin formation, in line with peroxidases activating monolignols for lignin polymerization. Time-course analyses coupled to candidate substrate-product pair network propagation revealed differential accumulation of low-molecular-weight phenolics, including (glycosylated) oligolignols, (glycosylated) flavonoids, and proanthocyanidins, in lignin-forming and H₂O₂-scavenging cultures and supported that monolignols are oxidatively coupled not only in the cell wall but also in the cytoplasm, where they are coupled to other monolignols and proanthocyanidins. Dilignol glycoconjugates with reduced structures were found in the culture medium, suggesting that cells are able to transport glycosylated dilignols to the apoplast. Transcriptomic analyses revealed that scavenging of apoplastic H₂O₂ resulted in remodulation of the transcriptome, with reduced carbon flux into the shikimate pathway propagating down to monolignol biosynthesis. Aggregated coexpression network analysis identified candidate enzymes and transcription factors for monolignol oxidation and apoplastic H₂O₂ production in addition to potential H₂O₂ receptors. The results presented indicate that the redox state of the apoplast has a profound influence on cellular metabolism.
Tree bark is a highly specialized array of tissues that plays important roles in plant protection and development. Bark tissues develop from two lateral meristems; the phellogen (cork cambium) ...produces the outermost stem–environment barrier called the periderm, while the vascular cambium contributes with phloem tissues. Although bark is diverse in terms of tissues, functions and species, it remains understudied at higher resolution.
We dissected the stem of silver birch (Betula pendula) into eight major tissue types, and characterized these by a combined transcriptomics and metabolomics approach. We further analyzed the varying bark types within the Betulaceae family.
The two meristems had a distinct contribution to the stem transcriptomic landscape. Furthermore, inter- and intraspecies analyses illustrated the unique molecular profile of the phellem. We identified multiple tissue-specific metabolic pathways, such as the mevalonate/betulin biosynthesis pathway, that displayed differential evolution within the Betulaceae. A detailed analysis of suberin and betulin biosynthesis pathways identified a set of underlying regulators and highlighted the important role of local, small-scale gene duplication events in the evolution of metabolic pathways.
This work reveals the transcriptome and metabolic diversity among bark tissues and provides insights to its development and evolution, as well as its biotechnological applications.
Anthocyanins are responsible for the color spectrum of both ornamental and natural flowers. However, not all plant species produce all colors. For example, roses are not blue because they do not ...naturally possess a hydroxylase that opens the pathway for delphinidin and its derivatives. It is more intriguing why some plants do not carry orange or scarlet red flowers with anthocyanins based on pelargonidin, because the precursor for these anthocyanins should be available if anthocyanins are made at all. The key to this is the substrate specificity of dihydroflavonol 4-reductase (DFR), an enzyme located at the branch point between flavonols and anthocyanins. The most common example is petunia, which does not bear orange flowers unless the enzyme is complemented by biotechnology. We changed a few amino acids in the active site of the enzyme and showed that the mutated petunia DFR started to favor dihydrokaempferol, the precursor to orange pelargonidin,
in vitro
. When transferred to petunia, it produced an orange hue and dramatically more pelargonidin-based anthocyanins in the flowers.
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