Number Of Stamens Research Articles

Unstable patterns of flower structure and development in the almost dioecious species Acer negundo (Sapindaceae, Sapindales)

Abstract Acer negundo L. is a wind-pollinated, dioecious tree that occasionally produces flowers with rudiments of the opposite sex. Both the male (staminate) and female (pistillate) flowers possess only two whorls: sepals and stamens or carpels, the arrangement of which is disputed. Here we present data on inflorescence and floral development, pollen fertility in staminodes and the diversity of male and female flowers. We found that the merism of male flowers is unstable, and the numbers of stamens and sepals vary independently. The different floral groundplans always occur within the inflorescences of the same generative shoot. The development of a flower begins with the initiation of sepals, but in female flowers, sepals are initiated sequentially and remain of different sizes, whereas in male flowers, sepals are initiated almost simultaneously and are equal. After the appearance of stamen primordia or carpel primordia, a part of the undifferentiated meristem remains. This unused meristem can be involved in producing staminodes or pistillodia. Both unisexual and (partly) bisexual flowers are found in the same inflorescence. Staminodes are either completely sterile or produce some amount of viable pollen. These features indicate the possibility of functional bisexuality in A. negundo.

A SUPERMAN-like Gene Controls the Locule Number of Tomato Fruit.

Tomato (Solanum lycopersicum) fruits are derived from fertilized ovaries formed during flower development. Thus, fruit morphology is tightly linked to carpel number and identity. The SUPERMAN (SUP) gene is a key transcription repressor to define the stamen-carpel boundary and to control floral meristem determinacy. Despite SUP functions having been characterized in a few plant species, its functions have not yet been explored in tomato. In this study, we identified and characterized a fascinated and multi-locule fruit (fmf) mutant in Solanum pimpinellifolium background harboring a nonsense mutation in the coding sequence of a zinc finger gene orthologous to SUP. The fmf mutant produces supersex flowers containing increased numbers of stamens and carpels and sets malformed seedless fruits with complete flowers frequently formed on the distal end. fmf alleles in cultivated tomato background created by CRISPR-Cas9 showed similar floral and fruit phenotypes. Our results provide insight into the functional conservation and diversification of SUP members in different species. We also speculate the FMF gene may be a potential target for yield improvement in tomato by genetic engineering.

Staurantherafloribunda, a new species of Gesneriaceae from Yunnan, China.

Staurantherafloribunda F.Su, C.Y.Hao & K.Tan, a new species of Gesneriaceae from Yunnan, China, is described and illustrated here. It is morphologically similar to S.grandifolia Benth. in the shape of corolla, stigma, leaves and the number of stamens. However, it can be readily distinguished from the compared species by its dense cymes, leaf indumentum, lack of a corolla spur, calyx colour and stamen shape. The description of the new species, photographs, detailed descriptions, notes on etymology, distribution and habitat, as well as comparisons with morphologically similar species, are provided.

Characterization and Gene Mapping of an Open-Glume Oryza sativa L. Mutant.

Floral organ development determines agricultural productivity by affecting seed development, seed quality, and final yield. In this study, we described the novel ogl mutant in rice (Oryza sativa L.), which is characterized by an open-glume phenotype, increased pistil number, reduced stamen number, decreased seed setting rate, and smaller rice grains. Genetic analysis showed that the open-glume phenotype might be controlled by a recessive qualitative trait locus. Employing bulked segregant analysis (BSA), one candidate region was identified on rice chromosome 1. The glume opening phenotype cosegregated with SNP (Chr1:1522703), which was located at the start codon of one transcript of OsJAG, resulting in partial loss of OsJAG function. cDNA analysis revealed that OsJAG encodes two transcript variants. Compared to normal plants, the expression of OsJAG.1 was upregulated in open-glume plants. When investigating the glume phenotype, we found that the expression of genes related to floral development changed greatly in open-glume plants. Taken together, this work increases our understanding of the developmental role of OsJAG in rice floral development.

Combined genome-wide association studies and expression quantitative trait locus analysis uncovers a genetic regulatory network of floral organ number in a tree peony (Paeonia suffruticosa Andrews) breeding population.

Great progress has been made in our understanding of floral organ identity determination and its regulatory network in many species; however, the quantitative genetic basis of floral organ number variation is far less well understood for species-specific traits from the perspective of population variation. Here, using a tree peony (Paeonia suffruticosa Andrews, Paeoniaceae) cultivar population as a model, the phenotypic polymorphism and genetic variation based on genome-wide association studies (GWAS) and expression quantitative trait locus (eQTL) analysis were analyzed. Based on 24 phenotypic traits of 271 representative cultivars, the transcript profiles of 119 cultivars were obtained, which indicated abundant genetic variation in tree peony. In total, 86 GWAS-related cis-eQTLs and 3188 trans-eQTL gene pairs were found to be associated with the numbers of petals, stamens, and carpels. In addition, 19 floral organ number-related hub genes with 121 cis-eQTLs were obtained by weighted gene co-expression network analysis, among which five hub genes belonging to the ABCE genes of the MADS-box family and their spatial-temporal co-expression and regulatory network were constructed. These results not only help our understanding of the genetic basis of floral organ number variation during domestication, but also pave the way to studying the quantitative genetics and evolution of flower organ number and their regulatory network within populations.

1H, 15N, and 13C backbone and side chain resonance assignments of the cold shock domain of the Arabidopsis thaliana glycine-rich protein AtGRP2.

AtGRP2 (Arabidopsis thaliana glycine-rich protein 2) is a 19-kDa RNA-binding glycine-rich protein that regulates key processes in A. thaliana. AtGRP2 is a nucleo-cytoplasmic protein with preferential expression in developing tissues, such as meristems, carpels, anthers, and embryos. AtGRP2 knockdown leads to an early flowering phenotype. In addition, AtGRP2-silenced plants exhibit a reduced number of stamens and abnormal development of embryos and seeds, suggesting its involvement in plant development. AtGRP2 expression is highly induced by cold and abiotic stresses, such as high salinity. Moreover, AtGRP2 promotes double-stranded DNA/RNA denaturation, indicating its role as an RNA chaperone during cold acclimation. AtGRP2 is composed of an N-terminal cold shock domain (CSD) followed by a C-terminal flexible region containing two CCHC-type zinc fingers interspersed with glycine-rich sequences. Despite its functional relevance in flowering time regulation and cold adaptation, the molecular mechanisms employed by AtGRP2 are largely unknown. To date, there is no structural information regarding AtGRP2 in the literature. Here, we report the 1H, 15N, and 13C backbone and side chain resonance assignments, as well as the chemical shift-derived secondary structure propensities, of the N-terminal cold shock domain of AtGRP2, encompassing residues 1-90. These data provide a framework for AtGRP2-CSD three-dimensional structure, dynamics, and RNA binding specificity investigation, which will shed light on its mechanism of action.

How do fertile stamens and staminodes go differently in Kingdonia uniflora? Evidence from stamen numbers, ontogeny, and structure

Kingdonia uniflora is in Circaeasteraceae and has fertile stamens and staminodes which are both variable in number; however, the differentiating process of these two types of stamens and the nectariferous structure of staminodes are still unclear. Variation in number and ontogeny (including the degeneration stage of staminodes) of stamens in K. uniflora are investigated under SEM, TEM and LM. The results indicate that there are 63 floral formulas in 80 flowers counted, and the most frequent flower floral formula (4 flowers) is P5A°11A5G6. The correlation between the stamen number and the total floral organ number is high (0.61), while the highest correlation with the total number of floral organs is the number of carpels, and there is a weak correlation between the two types of stamens (-0.23). The stamen development period is divided into five stages, with differentiation of stamens occurring at stage 2. The anther wall formation of fertile stamens is of the basic type, and the simultaneous meiosis form tetrahedral tetrads, while mature pollens are 2-celled and tricolpate. Sporogenous tissue of staminodes fails to develop further at an earlier stage, without the formation of secondary sporogenous cells. The head of mature staminodes has nectary tissue consisting of the secretory epidermis (two types of secretory cells), nectary parenchyma (about 15 layers) and vascular tissue with vessel and sieve tube elements. There are well-developed microchannels in epidermal cell walls, and the cells related to secreting nectar are rich in mitochondria, endoplasmic reticula and small vesicles. In addition, microsporogenesis, male gametophyte development, the secretory function of staminodes, and other characteristics in K. uniflora are similar to those in Ranunculaceae. This study clarifies the differentiating stage of fertile stamens and staminodes and explores the new structure (nectary) that staminodes formed, and also, it enriched the secretion modes in Ranunculales.

A dated phylogeny of the Neotropical Dipterygeae clade reveals 30 million years of winged papilionate floral conservatism in the otherwise florally labile early-branching papilionoid legumes

Abstract The early-branching clades of Fabaceae subfamily Papilionoideae are characterized by their remarkable lability in floral architecture. In contrast, more derived papilionoid lineages are marked by evolutionary conservatism towards strongly bilateral, papilionate flowers. Here, we show an unexpected example of conservatism of a unique floral architecture during the early diversification history of the papilionoids. We built the most comprehensively sampled molecular phylogenetic tree with a focus on the early-diverging papilionoid Dipterygeae clade to evaluate conservatism of the winged papilionate architecture and associated traits related to flower specialization (e.g. zygomorphy, petal differentiation, stable stamen number and stamen sheath). Dipterygeae comprise c. 22 species of mostly giant trees from across tropical forests in Central America and the Amazon, but they are also ecologically dominant in the savannas of the Brazilian Central Plateau. Phylogenetic analyses of nuclear ribosomal ITS/5.8S and plastid matK and trnL intron sequences strongly supported inter-relationships and the monophyly of each genus (Dipteryx, Monopteryx, Pterodon and Taralea). Bayesian relaxed-clock dating and a Bayesian model of ancestral character estimation revealed c. 30 Myr of conservatism of all winged papilionate-related flower traits in a clade comprising the most recent common ancestor of Dipteryx, Pterodon and Taralea, but lability in fruit morphology during the diversification of the entire Dipterygeae clade. Despite Monopteryx and remaining Dipterygeae being florally discrepant, they are collectively defined by a floral synapomorphy that is unique among all papilionoid Fabaceae: the highly differentiated calyx, where the two upper lobes are enlarged and wing-like, whereas the other three lower lobes are reduced. We suggest that the different dispersal strategies and the ancient winged papilionate floral conservatism in Dipterygeae, which has maintained effective ecological interactions with specialized pollinators and ensured the protection of young flower buds and developing fruits, may explain successful evolutionary and ecological persistence of the clade across the main Neotropical biomes.

Floral Abnormality of Bauhinia variegata Trees (Case study)

Background: Floral abnormality is one of the strange and exceptional phenomena, which gives popularity and attractiveness to ornamental flowers, although its causes are still a source of disagreement among many scientists.This study was carried out with the aim of documenting floral abnormality in Bauhinia variegata trees for the first time worldwide.
 Materials and Methods: Bauhinia variegata trees were monitored and monitored for seasons 2021-2022 in three locations in the city of Al-Bayda - eastern Libya, and flower abnormalities were documented photographically.
 Results: The results showed the registration of a new pattern of Bauhinia variegata after about 32 years of cultivation in of Al-Bayda city, libya with a clear increase in the number of petals (6-7-8 petals) superimposed (double) or contiguous, by up to 20% for each branch, with two petals often mottled, this mottled rarely disappears, the results also showed an increase in the number of stamens, and the emergence of some of them bilaterally incorporate with one of them turning into a petal.
 Conclusion: The cause of this abnormality is believed to be the drop in temperature during the two study seasons.

Studies on Flowering Characteristics and Floral Morphology of Some Jamun Genotypes (Syzygium cuminii Skeels) under Semi-arid Lateritic Belt of West Bengal, India

A study was conducted to find out the variability of flowering behaviour and floral morphology of randomly selected 10 jamun genotypes (Syzygium cuminii Skeels) from 3 diferent districts namely Bankura, Purulia and Paschim Bardhaman under semi-arid lateritic belt of West Bengal during the year 2022. Only a single plant was considered for a single accession which was taken under the study. The selection was done on random basis. Significant variation has been observed among the genotypes for the flowering behaviour as well as morphological characters of flowers. Month of panicle emergence among the selected genotypes ranged from 1st week of March to last week of March. Time taken for bud development was observed 21 (days from panicle emergence) from three accessions like JA 9 was shortest among 10 jamun accessions studied. Longest time for bud development was observed in JA 4 (38 days). Duration of flowering was highest of 39 days in genotype JA 6 followed by 35 days in JA 10and 34 days in JA 4. The length of panicle was recorded longest from JA 1 (13.08 cm) and shortest in JA 2 (6.73 cm). Highest flower length was measured from JA 2 (26.39 mm) and lowest from JA 8 (8.31). Maximum number of branchlets per panicle was recorded from accessions like JA 1 (15.02) and it was least in JA 8 (7.39). Maximum number of flowers per branchlets was observed from JA 7 (12.07) followed by JA 4 (11.09). Number of stamens per flower varied between 58.04 and 67.07. The flower colour of all accessions was light yellow except JA 3(pale green). On the basis of this significant findings it can be conclude that the genotype JA 1 has most earliest flowering and biggest size flower from JA 2.

SEXUAL POLYMORPHISM OF <i>RANUNCULUS CASSUBICUS</i> (RANUNCULACEAE) IN MOSCOW REGION

For the first time, gynodioecy is described in a perennial herbaceous polycarpic plant Ranunculus cassubicus L. (Kashubian buttercup) in the Moscow Region. It was revealed that R. cassubicus forms three types of flowers differing in the androecium structure: perfect (with fertile stamens and carpels), partially male-sterile (the number of stamens varies greatly and is much less than in perfect flowers), and pistillate ones (stamens completely missing). The sizes of flowers and their parts decrease in many studied parameters in the following row: perfect – partially male-sterile – pistillate. The studied 12 populations included six types of individuals forming: 1) only perfect flowers (83.1–89.2% of the total number of generative plants); 2) perfect and partially male-sterile flowers (4.0–6.5%); 3) only partially male-sterile flowers (2.8–3.9%); 4) perfect and pistillate flowers (1.4–2.6%); 5) pistillate and partially male-sterile flowers (1.2–2.9%); 6) only pistillate flowers (0.6–1.5%). It is established that over three years of observations (2020–2022), individuals of different sexual forms did not change the sex of flowers, and the sexual structure of populations remained stable, without sharp fluctuations.

Morphological and biochemical characterization of mango (Mangifera indica L.) genotypes under high density planting system

Experiment on evaluation of mango genotypes under high density planting system was conducted in six mango varieties of the same age group (5 years). The observation on tree characters indicated that the trunk circumference ranged from 20.51 cm (Prior) to 31.29 cm (Chandrakaran) and crown diameter ranged from 2.39 m (Ratna) to 3.09 m (Vellaikolumban). The qualitative data on morphological characters viz., tree, leaf, inflorescence, fruit, stone and seed characters were grouped into clusters based on the IPGRI descriptor. The observation on leaf characters revealed that the leaf blade length varied from 19.17 cm (Muvandan) to 25.40 cm (Ratna), leaf blade width ranged from 4.84 cm (Muvandan) to 7.68 cm (Vellaikolumban) and leaf petiole length varied from 2.29 cm (Chandrakaran) to 4.18 cm (Vellaikolumban). Based on the inflorescence characters studied, it was found that inflorescence length varied from 22.14 cm (Prior) to 36.47 cm (Vellaikolumban), hermaphrodite flowers ranged from 33.40% (Muvandan) to 85.80% (Chandrakaran) and number of stamens varied from 3 to 4. The observation on fruit characters revealed that the fruit length varied from 7.49 cm (Chandrakaran) to 18.71 cm (Mallika), fruit diameter ranged from 13.18 cm (Chandrakaran) to 25.25 cm (Mallika), fruit weight ranged from 8.93 g (Muvandan) to 24.69 g (Mallika), yield per tree ranged from 8.93 kg/tree (Muvandan) to 24.69 kg/tree (Mallika), and shelf life of fruits varied from 4 to 6 days. The observations on stone and seed characters revealed that Chandrakaran recorded the lowest stone length (5.58 cm), stone width (3.36 cm), stone thickness (1.23 cm), stone weight (17.79 g) and seed length (4.05 cm). The lowest seed width and seed weight was recorded by Prior (3.07cm) and Vellaikolumban (9.44 cm). The highest stone length was recorded by Mallika (11.67 cm), stone width by Ratna (8.67 cm), stone thickness by Vellaikolumban (2.19 cm), stone weight by Mallika (44.33 g), seed weight by Prior (22.22 g) and seed length and width by Ratna (7.91 cm and 8.47 cm respectively). From the fruit analysis conducted for assessing the quality attributes of different mango genotypes grown under high density planting system TSS ranged from 14.78 oBrix (Muvandan), acidity varied from 0.02% (Mallika) to 0.07% (Muvandan), ascorbic acid varied from 28.26 mg 100g-1(Vellaikolumban) to 79.68 mg 100g-1 (Chandrakaran), carotenoids ranged from 1.40 mg 100g-1 (Vellaikolumban) to 4.80 mg 100 g-1 (Ratna), and ß carotene ranged from 13.54 mg 100g-1 (Vellaikolumban) to 39.93 mg 100g-1(Ratna). The results on sensory indicated that Ratna variety of mango as the best one as it recorded the highest rank for colour, flavour, sweetness, texture and taste, as Mallika recorded the highest rank only for appearance. Wide variability was observed for the vegetative, floral, fruit and biochemical characters among the mango genotypes.

SUPERMAN strikes again in legumes.

The SUPERMAN (SUP) gene was described in Arabidopsis thaliana over 30 years ago. SUP was classified as a cadastral gene required to maintain the boundaries between reproductive organs, thus controlling stamen and carpel number in flowers. We summarize the information on the characterization of SUP orthologs in plant species other than Arabidopsis, focusing on the findings for the MtSUP, the ortholog in the legume Medicago truncatula. M. truncatula has been widely used as a model system to study the distinctive developmental traits of this family of plants, such as the existence of compound inflorescence and complex floral development. MtSUP participates in the complex genetic network controlling these developmental processes in legumes, sharing conserved functions with SUP. However, transcriptional divergence between SUP and MtSUP provided context-specific novel functions for a SUPERMAN ortholog in a legume species. MtSUP controls the number of flowers per inflorescence and the number of petals, stamens and carpels regulating the determinacy of ephemeral meristems that are unique in legumes. Results obtained in M. truncatula provided new insights to the knowledge of compound inflorescence and flower development in legumes. Since legumes are valuable crop species worldwide, with high nutritional value and important roles in sustainable agriculture and food security, new information on the genetic control of their compound inflorescence and floral development could be used for plant breeding.

IiSVP of Isatis indigotica can reduce the size and repress the development of floral organs.

IiSVP of Isatis indigotica was cloned and its expression pattern was analyzed. Ectopic expression of IiSVP in Arabidopsis could delay the flowering time and reduce the size of the floral organs. SVP (SHORT VEGETATIVE PHASE) can negatively regulate the flowering time of Arabidopsis. In the present work, the cDNA of IiSVP, an orthologous gene of AtSVP in I. indigotica, was cloned. IiSVP was highly expressed in rosette leaves, inflorescences and petals, but weakly expressed in sepals, pistils and young silicles. The results of subcellular localization showed that IiSVP was localized in nucleus. Bioinformatics analysis indicated that this protein was a MADS-box transcription factor. Constitutive expression of IiSVP in Arabidopsis thaliana resulted in decrease of the number of petals and stamens, and curly sepals were formed. In IiSVP transgenic Arabidopsis plants, obvious phenotypic variations in flowers could be observed, especially the size of the floral organs. In comparison with the wild-type plants, the size of petals, stamens and pistil in IiSVP transgenic Arabidopsis plants was decreased significantly. In some transgenic plants, the petals were wrapped by the sepals. Yeast two-hybrid experiments showed that IiSVP could form higher-order complexes with other MADS proteins, including IiSEP1, IiSEP3, IiAP1 and IiSEP4, but could not interact with IiSEP2. In this work, it was proved that the flowering process and the floral development in Arabidopsis could be affected by IiSVP from I. indigotica Fortune.

Significance of floral axis and staminal features in tracing phylogeny of Cleome species

Taxonomic delimitation, phylogeny of Cleome L. species and relative closeness between three allied families, Capparaceae, Cleomaceae and Brassicaceae, are enigmatic and yet to be resolved comprehensively. The genus Cleome of Cleomaceae represents a cosmopolitan assemblage of species with wide variability in morphological features sharing morphological similarity with both Capparaceae and Brassicaceae. In the present study, floral-axis and staminal features, along with habit and leaf characters, were employed in tracing the phylogeny of Cleome species not explored earlier. The parameters proved unique in solving the phylogenetic puzzle of Cleome, allowing to speculate on the origin of woody and non-woody herbaceous species of Cleome from two separate species aggregates of Capparaceae (palmate-leaved Crateva aggregate and simple-leaved Capparis aggregate, respectively), also to establish phylogenetic linkage between three families, Capparaceae, Cleomaceae and Brassicaceae. Evolutionary changes were directed towards the gradual shortening and suppression of elongated floral axis to discoid thalamus, gradual reduction in the number and size of stamens, and flower size with habitual transformations from shrubby to herbaceous form. Cleome appeared as a connecting link between Capparaceae and Brassicaceae, and the interpretations derived showed significant concomitance with APG IV classification system.

Oreocharisqianyuensis, a new species of Gesneriaceae from Southwest, China based on morphological and molecular evidence.

Oreocharisqianyuensis, a new species of Gesneriaceae from Southwest, China, is described and illustrated based on morphological comparisons and molecular phylogenetic analyses. Phylotranscriptomic analyses of the new species in the context of a comprehensive phylogeny with dense sampling of 88% (111/126) of all species of the genus indicated that the new species was most closely-related to O.fargesii. The new species is morphologically similar to O.fargesii and O.nanchuanica in the shape, color and structure of flowers and the number of stamens, but differs in the leaf blade shape, margin and the indumentum characters of the inflorescence. Its morphological relationship with similar species is discussed, the detailed descriptions, colour photographs, distribution, as well as the IUCN threatened status based on the IUCN Red List Categories and Criteria are also provided.

 Hydrangeamarunoi (Hydrangeaceae), a new species from Osumi Peninsula, southern Japan.

Hydrangeamarunoi Tagane & S. Fujii, from the Kimotsuki Mountains in the Ohsumi Peninsula, southern Japan, is described and illustrated. It is morphologically similar to H.alternifolia in having three-petaloid calyx lobes in marginal flowers, but is distinguished by the larger stamen number, and longer styles and seeds. Multiplex ISSR genotyping by sequencing (MIG-seq) demonstrated that the new species is monophyletic and closely related to H.amamiohsimensis and H.moellendorffii rather than H.alternifolia.

Disruptive selection via pollinators and seed predators on the height of flowers on a wind-dispersed alpine herb.

Floral stalk height is known to affect seed dispersal of wind-dispersed grassland species, but it may also affect the attractiveness of flowers and fruits of animal-pollinated and animal-dispersed plants. Stalk height may thus be responsive to selection via interactions with both mutualist pollinators and seed dispersers, but also antagonist florivores and seed predators. In this study, we aimed to determine the effect of pollinators and seed predators on selection on floral stalk height in the insect-pollinated and wind-dispersed, alpine, andromonoecious herb Pulsatilla alpina, whose flowers also vary in their sex allocation and thus in the resources available to both mutualists and antagonists. We measured the resource status of individuals in terms of their size and the height of the vegetation surrounding plants of P. alpina at 11 sites. In one population, we recorded floral stalk height over an entire growing season and investigated its association with floral morphology and floral sex allocation (pistil and stamen number) and used leaf-removal manipulations to assess the effect of herbivory on floral stalk height. Finally, in four populations, we quantified phenotypic selection on floral stalk height in four female components of reproductive success before seed dispersal. Stalk height was positively associated with female allocation of the respective flower, the resource status of the individual, and the height of the surrounding vegetation, and negatively affected by leaf removal. Our results point to disruptive selection on stalk height in terms of both selection differentials and selection gradients for fertilization, seed predation, and seed maturation rates and to positive selection on stalk height in terms of a selection differential for mature seed number. Stalk height of P. alpina is a costly trait that affects female reproductive success via interactions with both mutualists and antagonists. We discuss the interplay between the resource status and selection imposed on female reproductive success and its likely role in the evolution of sex-allocation strategies, especially andromonoecy.

Disruption of transcription factor RhMYB123 causes the transformation of stamen to malformed petal in rose (Rosa hybrida)

We find that the R2R3 MYB transcription factor RhMYB123 has a novel function to regulate stamen-petal organ specification in rose. Rose is one of the ornamental plants with economic importance worldwide. Malformed flower seriously affects the ornamental value and fertility of rose. However, the regulatory mechanism is largely unknown. In this work, we identified a R2R3 MYB transcription factor RhMYB123 from rose, the expression of which significantly decreased from flower differentiation stage to floral organ development stage. Phylogenetic analysis indicated that it belongs to the same subgroup as MYB123 of Arabidopsis and located in nucleus. In addition, RhMYB123 was confirmed to have transcriptional activation function by dual luciferase assay. Silencing RhMYB123 using Virus-Induced Gene Silencing (VIGS) in rose could increase the number of malformed petaloid stamen. Furthermore, we identified 549 differential expressed genes (DEGs) in TRV-RhMYB123 lines compared to TRV controls by RNA-seq of floral buds (flower differentiation stage). Among of those genes, expression of 3 MADS box family genes related to floral organ development reduced in TRV-RhMYB123 lines, including AGAMOUS (RhAG), AGAMOUS LIKE 15 (RhAGL15), and SHATTERPROOF 1 (RhSHP1). Given, previous studies have shown that auxin plays a crucial role in floral meristem initiation and stamen-petal organ specification. We also found 6 DEGs were involved in auxin signal transduction, of which five were reduced expression in TRV-RhMYB123. Taken together, our findings suggested that RhMYB123 may govern the development of malformed petaloid stamen by regulating the expressions of some MADS box family members and auxin signaling pathway elements.

The maximum and the minimum: two new species of Tovomita Aubl. (Clusiaceae) from the Guiana Shield with an unusual number of stamens

Le maximum et le minimum: deux nouvelles espèces de Tovomita Aubl. (Clusiaceae) du Plateau des Guyanes avec un nombre inhabituel d'étamines. Deux nouvelles espèces de Tovomita Aubl. (Clusiaceae) du Bouclier Guyanais sont décrites et illustrées. Tovomita maxima Molino & J.Engel, sp. nov., connue de Guyane française, du Guyana et du Brésil, se distingue par sa grande taille (jusqu'à 30 m de hauteur), ses grandes feuilles à nervation eucamptodrome, ses bractéoles calyptrées et une variation inhabituelle du nombre d'étamines (74-145). Tovomita saulensis J.Engel & Molino, sp. nov., apparemment endémique du centre de la Guyane française, est un arbre de sous-bois avec de petites feuilles à nervation brochidodrome et des fleurs avec peu d'étamines (9-15). Des illustrations, descriptions, photographies in vivo, un statut de conservation préliminaire, une carte de distribution et des commentaires sur la morphologie des espèces apparentées sont fournis.