Floral Symmetry Research Articles

The realignment of Acosmium sensu stricto with the Dalbergioid clade (Leguminosae: Papilionoideae) reveals a proneness for independent evolution of radial floral symmetry among early­branching papilionoid legumes

AbstractThe genus Acosmium s.l. (Leguminosae: Papilionoideae) traditionally included up to 20 tree species mostly from South America. Due mainly to radial floral symmetry, the taxonomy of Acosmium has been historically confounded with four other Papilionoideae genera: Dicraeopetalum, Guianodendron,Leptolobium, and Sweetia. We used comprehensively sampled molecular data from the nuclear ribosomal internal transcribed spacer (ITS/5.8S) and two plastid DNA (matK, trnL intron) regions in order to evaluate the monophyly of Acosmium s.l. and to shed light on the relationships of its distinct lineages in the context of the Papilionoideae phylogeny. Parsimony and Bayesian analyses of all data concurred in resolving a polyphyletic Acosmium s.l. Our data agreed with previous molecular phylogenetic analyses that resolved Dicraeopetalum and Sweetia apart from Acosmium s.l. Unexpectedly, Acosmium s.str., thought to belong to the Genistoid clade, is here strongly resolved within the Dalbergioid Pterocarpus clade. Despite being classified until recently as different sections of Acosmium s.l., Leptolobium and Guianodendron were resolved within the Genistoid clade as part of a Bowdichia clade with the genera Diplotropis and Bowdichia. Our results reveal that radial floral symmetry has evolved independently in all Acosmium segregates and strongly suggest that the primacy given to floral characters involving corolla symmetry and petal differentiation in traditional legume classification has often obscured phylogenetic relationships.

CanMEDs and the discourse of nature: on petals, beauty and the symmetry of flowers

N/A

Geometric morphometrics of corolla shape: dissecting components of symmetric and asymmetric variation inErysimum mediohispanicum(Brassicaceae)

Symmetry is an important feature of floral structure, and floral symmetries are diverse and often complex. We use a new morphometric approach for analysing shapes with complex types of symmetry, which partitions shape variation into a component of symmetric variation and different components of asymmetry. This approach, based on the mathematical theory of symmetry groups, can be used for landmark configurations with any type of symmetry and is therefore promising as a general framework for morphometric analyses of floral symmetry and asymmetry. We demonstrate this approach by quantifying floral shape variation in a wild population of Erysimum mediohispanicum (Brassicaceae). Flowers of this species are disymmetric, so that the symmetry in the left-right and adaxial-abaxial directions can be considered separately and in combination. Both principal component analysis and Procrustes ANOVA indicate that symmetric variation accounts for most of the total variance and that adaxial-abaxial asymmetry is the dominant component of fluctuating asymmetry. Each component is associated with specific patterns of shape variation. These results illustrate the potential of the new method and suggest new areas for future research. The new morphometric approach is promising for further analyses of floral symmetry and asymmetry in evolutionary and developmental contexts.

Comparative Morphology and Anatomy of Floral Symmetry in Legumes (Fabaceae)

Information from phylogenetic trees implies zygomorphic flowers have evolved independently from their actinomorphic ancestors several times. There are various types of zygomorphic flowers in the legume subfamilies Caesalpinioideae and Papilionoideae. To understand the relationship between the cell number and size in the petals of zygomorphic flowers, the comparative morphology and anatomy of flower petals were examined in Cercis chinensis and Caesalpinia decapetala var. japonica in Caesalpinioideae, and Lespedeza formosa subsp. velutina and Pueraria lobata in Papilionoideae. Increased petal size is correlated to a higher number and/or size of the cells of the petal in Caesalpinioideae. The characteristics flower morphology of the Papilionoideae has evolved by increased cell numbers, although the cell size was the smallest. Papilionoideae has characteristic papilionoid flowers consisting of five specialised petals. These characteristic morphologies were generated from the complicated changing pattern of cells in petals in the course of legume diversification.

Celebrating Giant Steps toward a Synthetic History of Angiosperm Evolution

Celebrating Giant Steps toward a Synthetic History of Angiosperm Evolution

ANTIBACTERIAL ACTIVITY OF GERANIUM PRATENSE PREPARATIONS

s. PHYTOPHARM 2012 M 64 Obzory po kliniceskoj farmacologii i lekarstvennoj terapii [Reviews of clinical pharmacology and drug therapy] ТОМ 10/2012/2 ANTIBACTERIAL ACTIVITY OF GERANIUM PRATENSE PREPARATIONS © Burakova M. A., Karavaeva A.V, Kauhova I. E., Razaryonova K. N., Zhokhova E. V. St. Petersburg State Chemical-Pharmaceutical Academy, Russia Geranium pratense is a perennial herb with horizontal rootstock, palmately lobed leaves and pentamerous zygomorphic bluish flowers, widespread in Russia. The chemical composition of the aerial part and root part of G. pratense includes hydrolysable and condensed tannins, phenolic acids, flavonoids. herb, rhizome and root of G. pratense in powder or by infusion or decoction are reportedly used in folk medicine in treatment of periodontal diseases and stomatitis. The aim of the present investigation was to determine optimal conditions for extraction of biologically active compounds from G. pratense, to evaluate antimicrobial activity of powdered extracts obtained from its aerial part and root part and to validate scientifically its use in traditional medicine. The plant matter (herb or rhizome and root of G. pratense, collected in 2010–2011 in Northwest Russia) was extracted with 40 % ethanol. Trials varying in methods of extraction, particle size, extraction time and solvent to solid ratio were performed. The quantitative evaluation of tannins and flavonoids in 40 % ethanol aqueous extracts and powdered extracts was carried out by spectrophotometric method. Results of assays were reported in gallic acid equivalents for tannins and rutin equivalents for flavonoids. broth dilution method followed by subculturing to agar media without antibacterial agent was employed to assess minimal inhibition concentration (MiC) and minimal bactericidal concentration (MbC). Optimal conditions for extraction of phenolic constituents from raw material were evaluated. Powdered herb extract (PhE) was reported to contain 33.05 % of tannins and 9.74 % of flavonoinds. Antimicrobial studies suggested that PhE had inhibitory effect against S. aureus and B. cereus: the MiC was found to be 2 mg/ml against S. aureus, the Mib against B. cereus was 1 mg/ml. The total content of tannins in powdered extract of G. pratense root part (PRE) is 41.56 %. PRE exhibited growth inhibitory activity against S. aureus, B. cereus and P. aeruginosa with Mib value of 0.5 mg/ml, 1 mg/ml and MiC value of 2 mg/ml respectively. PhE and PRE revealed antimicrobial activity against Gram-positive bacteria. The existence of microorganisms in particular Streptococcus sp. in an oral biofilm and dental plaque has profound implications for the etiology of periodontal disease. So the results indicate that the studied G. pratense preparations could become a new effective agent in a wide range of oral care products used in treatment-and-profilactic of periodontitis, gingivitis and stomatitis. DEVELOPMENT OINTMENT AND SUPPOSITORY WITH HYPERICUM PERFORATUM HERB POLYEXTRACT © Teslev A. A., Vainshtein V. A., Kaukhova I.Ye., Tsygankova M. I., Hazzaa I. H. St. Petersburg State Chemical-Pharmaceutical Academy, Russia hypericum perforatum herb (John’s wort) contains a variety of biologically active substances (bAS), such as hypericin, pseudohypericin, hyperforin, flavonoids, carotenoids, vitamins, etc. Great “ensemble” of St. John’s wort’s bAS causes a wide range of its therapeutic action. There are not technologies a soft pharmaceutical form with hydroalcoholic and oil extracts of the hypericum perforatum herb. The aim of the study is to develop the technology the composition of ointments and suppositories with St. John’s wort herb extracts in the amount of 1:1 or more in dosage forms. The first stage is the extraction of dry St. John’s wort herb by solvents with increasing polarity — acetone, aqueous solutions of different concentrations of ethanol. in this case сhlorophylls, anthracene derivatives, flavonoids are extracted. liquid extracts were pooled and evaporated in the rotary vacuum evaporator until one-third of the volume. The components of ointment or suppository bases (COSb) (there are oils, polyethylene oxide, emulsifiers: Mhd, tween-80, apian wax, witepsol etc.) were added in the evaporator flask. The total amount of the COSb was selected according to the source of plant material to obtain the desired module of the extract — 1:1 or 1:2. The evaporation was stopped when the distillation of volatile fraction was over. The residue after distillation of the extractant is a thick mass with soft or solid consistency, which can be easily melted and added into the ointments or suppositories. The content in the extract anthracenederivarives COSb was from 30 to 130 mg %, and flavonoids — from 0.30 to 2.0 % depending on the module of extraction.

Progress in the study of floral symmetry

Progress in the study of floral symmetry

Similar Genetic Mechanisms Underlie the Parallel Evolution of Floral Phenotypes

The repeated origin of similar phenotypes is invaluable for studying the underlying genetics of adaptive traits; molecular evidence, however, is lacking for most examples of such similarity. The floral morphology of neotropical Malpighiaceae is distinctive and highly conserved, especially with regard to symmetry, and is thought to result from specialization on oil-bee pollinators. We recently demonstrated that CYCLOIDEA2–like genes (CYC2A and CYC2B) are associated with the development of the stereotypical floral zygomorphy that is critical to this plant–pollinator mutualism. Here, we build on this developmental framework to characterize floral symmetry in three clades of Malpighiaceae that have independently lost their oil bee association and experienced parallel shifts in their floral morphology, especially in regard to symmetry. We show that in each case these species exhibit a loss of CYC2B function, and a strikingly similar shift in the expression of CYC2A that is coincident with their shift in floral symmetry. These results indicate that similar floral phenotypes in this large angiosperm clade have evolved via parallel genetic changes from an otherwise highly conserved developmental program.

Genetic Analysis of Floral Symmetry in Van Gogh's Sunflowers Reveals Independent Recruitment of CYCLOIDEA Genes in the Asteraceae

The genetic basis of floral symmetry is a topic of great interest because of its effect on pollinator behavior and, consequently, plant diversification. The Asteraceae, which is the largest family of flowering plants, is an ideal system in which to study this trait, as many species within the family exhibit a compound inflorescence containing both bilaterally symmetric (i.e., zygomorphic) and radially symmetric (i.e., actinomorphic) florets. In sunflower and related species, the inflorescence is composed of a single whorl of ray florets surrounding multiple whorls of disc florets. We show that in double-flowered (dbl) sunflower mutants (in which disc florets develop bilateral symmetry), such as those captured by Vincent van Gogh in his famous nineteenth-century sunflower paintings, an insertion into the promoter region of a CYCLOIDEA (CYC)-like gene (HaCYC2c) that is normally expressed specifically in WT rays is instead expressed throughout the inflorescence, presumably resulting in the observed loss of actinomorphy. This same gene is mutated in two independent tubular-rayed (tub) mutants, though these mutations involve apparently recent transposon insertions, resulting in little or no expression and radialization of the normally zygomorphic ray florets. Interestingly, a phylogenetic analysis of CYC-like genes from across the family suggests that different paralogs of this fascinating gene family have been independently recruited to specify zygomorphy in different species within the Asteraceae.

Virus-induced gene silencing (VIGS) in Cysticapnos vesicaria, a zygomorphic-flowered Papaveraceae (Ranunculales, basal eudicots)

Studies of evolutionary diversification in the basal eudicot family Papaveraceae, such as the transition from actinomorphy to zygomorphy, are hampered by the lack of comparative functional studies. So far, gene silencing methods are only available in the actinomorphic species Eschscholzia californica and Papaver somniferum. This study addresses the amenability of Cysticapnos vesicaria, a derived fumitory with zygomorphic flowers, to virus-induced gene silencing (VIGS), and describes vegetative and reproductive traits in this species. VIGS-mediated downregulation of the C. vesicaria PHYTOENE DESATURASE gene (CvPDS) and of the FLORICAULA gene CvFLO was carried out using Agrobacterium tumefaciens transfer of Tobacco rattle virus (TRV)-based vectors. Wild-type and vector-treated plants were characterized using reverse transcription-PCR (RT-PCR), in situ hybridization, and macroscopic and scanning electron microscopic imaging. Cysticapnos vesicaria germinates rapidly, can be grown at high density, has a short life cycle and is self-compatible. Inoculation of C. vesicaria with a CvPDS-VIGS vector resulted in strong photobleaching of green parts and reduction of endogenous CvPDS transcript levels. Gene silencing persisted during inflorescence development until fruit set. Inoculation of plants with CvFLO-VIGS affected floral phyllotaxis, symmetry and floral organ identities. The high penetrance, severity and stability of pTRV-mediated silencing, including the induction of meristem-related phenotypes, make C. vesicaria a very promising new focus species for evolutionary-developmental (evo-devo) studies in the Papaveraceae. This now enables comparative studies of flower symmetry, inflorescence determinacy and other traits that diversified in the Papaveraceae.

Can Nectar Be a Disadvantage? Contrasting Pollination Natural Histories of Two Woody Violaceae from the Neotropics

We present the first pollination data on Neotropical species of Violaceae with actinomorphic flowers. Floral biology of Paypayrola blanchetiana and Amphirrhox longifolia were studied in Brazilian Atlantic rainforest. Petals of both species form a corolla tube, restricting access to floral rewards to visitors with long mouth parts. Flowers lack a spur, common in zygomorphic Violaceae, to store nectar. Both species’ flowers open in the evening and continue flowering during daytime. They emit a sweet scent dominated by benzenoid and monoterpenoid compounds. While A. longifolia flowers are nectarless, flowers of P. blanchetiana produce nectar throughout anthesis. A wide range of night- and day-active visitors, including moths, bees, and butterflies, were observed at P. blanchetiana; 68% of all nocturnal visits took place at dawn. Fruit set of P. blanchetiana was extraordinarily low. Nectar production and pollen presentation occur in close proximity, and pollen dissolves in accumulating nectar. After contact with nectar, experimental pollen germination rates were near 0. Amphirrhox longifolia flowers received few visits by diurnal and nocturnal bees and pollen-collecting Heliconius butterflies. Fruit set was still low (11%) but was ten times higher than that in P. blanchetiana (1%). Low fruit set seems to result from diminished pollen viability through nectar contact in P. blanchetiana and pollinator limitation in A. longifolia.

Lecythidaceae Poit. in the Tupé Sustainable Development Reserve, Manaus, Brazil

Lecythidaceae is the family of the Brazil nut, and comprises about 300 species belonging to 17 genera with pantropical distributions. One hundred and twenty-two species belonging to nine genera are distributed throughout Brazil, demonstrating its greatest diversity in the Amazon rainforest where Lecythidaceae is also one of the most abundant families. It is usually difficult to collect fertile material from these trees because of their canopy heights, and species determinations using sterile material can be complex because of their morphological similarities. There have been relatively few studies of this family even though it is one of the most important groups in the Amazon region, and a detailed taxonomic treatment of the species of Lecythidaceae in the Tupe Sustainable Development Reserve was therefore the goal of the present work. Ten species were found, Allantoma lineata (Mart. ex O.Berg) Miers, Bertholletia excelsa Bonpl., Couratari tenuicarpa A.C.Sm., Lecythis poiteaui O. Berg; and six species of Eschweilera, the richest genus. The descriptions and identification keys of the species used 56 characters. The main reproductive characters useful for distinguishing the species were the pubescence of the inflorescence rachis, pedicel length and trichomes presence, floral symmetry, hood type, filament shape, stigma shape, fruit shape and size, and aril type. The most diagnostic vegetative characters were the type and color of the outer bark, inner bark color, midrib prominence, and petiole shape and pubescence.

Parallel evolution of TCP and B-class genes in Commelinaceae flower bilateral symmetry.

BackgroundFlower bilateral symmetry (zygomorphy) has evolved multiple times independently across angiosperms and is correlated with increased pollinator specialization and speciation rates. Functional and expression analyses in distantly related core eudicots and monocots implicate independent recruitment of class II TCP genes in the evolution of flower bilateral symmetry. Furthermore, available evidence suggests that monocot flower bilateral symmetry might also have evolved through changes in B-class homeotic MADS-box gene function.MethodsIn order to test the non-exclusive hypotheses that changes in TCP and B-class gene developmental function underlie flower symmetry evolution in the monocot family Commelinaceae, we compared expression patterns of teosinte branched1 (TB1)-like, DEFICIENS (DEF)-like, and GLOBOSA (GLO)-like genes in morphologically distinct bilaterally symmetrical flowers of Commelina communis and Commelina dianthifolia, and radially symmetrical flowers of Tradescantia pallida.ResultsExpression data demonstrate that TB1-like genes are asymmetrically expressed in tepals of bilaterally symmetrical Commelina, but not radially symmetrical Tradescantia, flowers. Furthermore, DEF-like genes are expressed in showy inner tepals, staminodes and stamens of all three species, but not in the distinct outer tepal-like ventral inner tepals of C. communis.ConclusionsTogether with other studies, these data suggest parallel recruitment of TB1-like genes in the independent evolution of flower bilateral symmetry at early stages of Commelina flower development, and the later stage homeotic transformation of C. communis inner tepals into outer tepals through the loss of DEF-like gene expression.

A transposon-mediate inactivation of a CYCLOIDEA-like gene originates polysymmetric and androgynous ray flowers in Helianthus annuus

In several eudicots, including members of the Asteraceae family, the CYCLOIDEA (CYC) genes, which belong to the TCP class of transcription factors, are key players for floral symmetry. The sunflower inflorescence is heterogamous (radiate capitulum) with sterile monosymmetric ray flowers located in the outermost whorl of the inflorescence and hermaphrodite polysymmetric disk flowers. In inflorescence of Heliantheae tribe, flower primordia development initiates from the marginal ray flowers while disk flowers develop later in an acropetal fashion in organized parastichies along a number found to be one of Fibonacci patterns. Mutants for inflorescence morphology can provide information on the role of CYC-like genes in radiate capitulum evolution. The tubular ray flower (turf) mutant of sunflower shows hermaphrodite ray flowers with a nearly polysymmetric tubular-like corolla. Here, we demonstrate that this mutation is caused by the insertion in the TCP motif of a sunflower CYC-like gene (HaCYC2c) of non-autonomous transposable element (TE), belonging to the CACTA superfamily of transposons. We named this element Transposable element of turf1 (Tetu1). The Tetu1 insertion changes the reading frame of turf-HaCYC2c for the encoded protein and leads to a premature stop codon. Although in Tetu1 a transposase gene is lacking, our results clearly suggest that it is an active TE. The excision of Tetu1 restores the wild type phenotype or generates stable mutants. Co-segregation and sequence analysis in progenies of F(2) and self-fertilized plants derived from reversion of turf to wild type clearly identify HaCYC2c as a key regulator of ray flowers symmetry. Also, HaCYC2c loss-of-function promotes the developmental switch from sterile to hermaphrodite flowers, revealing a novel and unexpected role for a CYC-like gene in the repression of female organs.

Chamerion or Chamaenerion (Onagraceae)? The old story in new words

AbstractWhen treated separately from Epilobium, the group of species with zygomorphic flowers and alternate leaves has the correct generic name Chamaenerion Ség. 1754, and Chamerion (Raf.) Raf. ex Holub 1972 is its later heterotypic synonym. The history of generic treatments and name changes in Epilobium s.l. is briefly discussed, and nomenclatural and type citations are provided.

Development of a Mobile Application, “Wild Flowers of Bukhansan National Park (version 1.0)”, for Identification of Plants in Bukhansan National Park

We developed the educational purpose mobile application, named “Wild Flowers of Bukhansan National Park (version 1.0)”, aiming for easy identification of wildflowers for students and visitors in the park. When visitors find a flower or part of plant in the park, visitors can search for its name utilizing the pictures and characters provided in their own smartphone mobile devices or tablet PCs. The application provides pictures of wildflowers in the park and character-based searching system based on 12 diagnostic features (e.g., growth form, leaf arrangement, flower symmetry, petal color, petal number, sepal number, etc). We adopted the complete floristic survey of Chung and Lee (1962) and added species that we confirmed their distribution in the park during the development of this application. In summary, number of vascular plants in this park was estimated to be 428 taxa including 100 families, 280 genera, 327 species, 1 subspecies, 50 varieties, and 5 formas. We provided a total of 588 pictures representing 358 taxa and each taxon includes multiple pictures in many cases. Included identification quizzes can be an efficient educational tool as well as fun activity for students and visitors who are learning plant species in Korea. Our next step will include GPS function in the application for indicating visitor's location and for providing previously reported sites of the species that we interested in the map of the park. The future application which includes GPS function will be a valuable tool for the monitoring of rare plants, plant researches related to the climate changes, etc. We currently provide Korean iPhone version only, and English version and both of android versions will be serviced soon.

Independent Origin of Radial Floral Symmetry in the Gloxinieae (Gesnerioideae: Gesneriaceae) is Supported by the Rediscovery of Phinaea pulchella in Cuba

Phinaea , in the currently accepted circumscription, is a genus in the flowering plant family Gesneriaceae with three widely dis- junct species. These species are known from small populations in Mexico, northern South America, and the West Indies (Cuba and Haiti), respectively. Phinaea pulchella is one of the few members of the tribe Gloxinieae that occurs naturally in the West Indies and it is the only mem- ber of the tribe endemic to that region. It was rediscovered in Cuba in 2008, more than fifty years after it was last documented. Results from molecular data generated from the nrDNA ITS and cpDNA trnL-F regions strongly support that P. pulchella does not group with other Phinaea species and instead shares a recent common ancestor with Diastema vexans in a clade that is sister to Pearcea and Kohleria . The phylogenetic placement of P. pulchella suggests that radial floral symmetry and buzz-pollination is autapmorphic in this taxon. Our results strongly support convergence of radial symmetry and associated characters with buzz-pollination in the following taxa in the tribe Gloxinieae: Niphaea , Phinaea s. s., Phinaea pulchella , and Amalophyllon . New generic circumscriptions based on the results presented here are not suggested until more com- plete taxon sampling includes additional species currently recognized in Amalophyllon .

The application of group theory to the description of pseudosymmetry

The application of group theory to the description of biological objects’ pseudosymmetry is proposed and substantiated by the example of the rotatory symmetry of actinomorphic and zygomorphic flowers. The problems of biosymmetrics terminology are considered, and point symmetry elements are characterized as applied to the description of floral symmetry. Fundamental provisions of group theory are stated. Application of the Curie principle to biological objects is described. Algorithms for the quantitative assessment of floral pseudosymmetry are given; the description is made of floral pseudosymmetry in terms of group theory, including the evolutionary aspect. The conclusion is made that adaptation of group theory to the description of biological objects’ symmetry (biosymmetrics) is important not only from the fundamental point of view but also as a tool of interdisciplinary mutual understanding among biologists, physicists, crystallographers, and other specialists whose communicative language is mathematics.

A double-flowered variety of lesser periwinkle (Vinca minor fl. pl.) that has persisted in the wild for more than 160 years

Homeotic transitions are usually dismissed by population geneticists as credible modes of evolution due to their assumed negative impact on fitness. However, several lines of evidence suggest that such changes in organ identity have played an important role during the origin and subsequent evolution of the angiosperm flower. Better understanding of the performance of wild populations of floral homeotic varieties should help to clarify the evolutionary potential of homeotic mutants. Wild populations of plants with changes in floral symmetry, or with reproductive organs replacing perianth organs or sepals replacing petals have already been documented. However, although double-flowered varieties are quite popular as ornamental and garden plants, they are rarely found in the wild and, if they are, usually occur only as rare mutant individuals, probably because of their low fitness relative to the wild-type. We therefore investigated a double-flowered variety of lesser periwinkle, Vinca minor flore pleno (fl. pl.), that is reported to have existed in the wild for at least 160 years. To assess the merits of this plant as a new model system for investigations on the evolutionary potential of double-flowered varieties we explored the morphological details and distribution of the mutant phenotype. The floral morphology of the double-flowered variety and of a nearby population of wild-type plants was investigated by means of visual inspection and light microscopy of flowers, the latter involving dissected or sectioned floral organs. The double-flowered variety was found in several patches covering dozens of square metres in a forest within the city limits of Jena (Germany). It appears to produce fewer flowers than the wild-type, and its flowers are purple rather than blue. Most sepals in the first floral whorl resemble those in the wild-type, although occasionally one sepal is broadened and twisted. The structure of second-whorl petals is very similar to that of the wild-type, but their number per flower is more variable. The double-flowered character is due to partial or complete transformation of stamens in the third whorl into petaloid organs. Occasionally, 'flowers within flowers' also develop on elongated pedicels in the double-flowered variety. The flowers of V. minor fl. pl. show meristic as well as homeotic changes, and occasionally other developmental abnormalities such as mis-shaped sepals or loss of floral determinacy. V. minor fl. pl. thus adds to a growing list of natural floral homeotic varieties that have established persistent populations in the wild. Our case study documents that even mutant varieties that have reproductive organs partially transformed into perianth organs can persist in the wild for centuries. This finding makes it at least conceivable that even double-flowered varieties have the potential to establish new evolutionary lineages, and hence may contribute to macroevolutionary transitions and cladogenesis.

Conserved differential expression of paralogous DEFICIENS‐ and GLOBOSA‐like MADS‐box genes in the flowers of Orchidaceae: refining the ‘orchid code’

In flowering plants, class-B floral homeotic genes encode MADS-domain transcription factors, which are key in the specification of petal and stamen identity, and have two ancient clades: DEF-like and GLO-like genes. Many species have one gene of each clade, but orchids have typically four DEF-like genes, representing ancient gene clades 1, 2, 3 and 4. We tested the 'orchid code', a combinatorial genetic model suggesting that differences between the organs of the orchid perianth (outer tepals, inner lateral tepals and labellum) are generated by the combinatorial differential expression of four DEF-like genes. Our experimental test involves highly sensitive and specific measurements, with qRT-PCR of the expression of DEF- and GLO-like genes from the distantly related Vanilla planifolia and Phragmipedium longifolium, as well as from wild-type and peloric Phalaenopsis hybrid flowers. Our findings support the first 'orchid code' hypothesis, in that absence of clade-3 and -4 gene expression distinguishes the outer tepals from the inner tepals. In contrast to the original hypothesis, however, mRNA of both clade-3 and -4 genes accumulates in wild-type inner lateral tepals and the labellum, and in labellum-like inner lateral tepals of peloric flowers, albeit in different quantities. Our data suggest a revised hypothesis where high levels of clade-1 and -2, and low levels of clade-3 and -4, gene expression specify inner lateral tepals, whereas labellum development requires low levels of clade-1 and -2 expression and high levels of clade-3 and -4 expression.