B-Function Expression in the Flower Center Underlies the Homeotic Phenotype of Lacandonia schismatica (Triuridaceae)

Spontaneous homeotic transformations have been described in natural populations of both plants and animals, but little is known about the molecular-genetic mechanisms underlying these processes in plants. In the ABC model of floral organ identity in Arabidopsis thaliana, the B- and C-functions are necessary for stamen morphogenesis, and C alone is required for carpel identity. We provide ABC model-based molecular-genetic evidence that explains the unique inside-out homeotic floral organ arrangement of the monocotyledonous mycoheterotroph species Lacandonia schismatica (Triuridaceae) from Mexico. Whereas a quarter million flowering plant species bear central carpels surrounded by stamens, L. schismatica stamens occur in the center of the flower and are surrounded by carpels. The simplest explanation for this is that the B-function is displaced toward the flower center. Our analyses of the spatio-temporal pattern of B- and C-function gene expression are consistent with this hypothesis. The hypothesis is further supported by conservation between the B-function genes of L. schismatica and Arabidopsis, as the former are able to rescue stamens in Arabidopsis transgenic complementation lines, and Ls-AP3 and Ls-PI are able to interact with each other and with the corresponding Arabidopsis B-function proteins in yeast. Thus, relatively simple molecular modifications may underlie important morphological shifts in natural populations of extant plant taxa

A nonet of novel species of Monanthotaxis (Annonaceae) from around Africa

As part of an ongoing revision of the genus Monanthotaxis Baill. (Annonaceae), nine new species are described and one variety is reinstated to species rank. Two new species from West Africa (Monanthotaxis aquila P.H. Hoekstra, sp. nov. and Monanthotaxis atewensis P.H. Hoekstra, sp. nov.), four new species from Central Africa (Monanthotaxis couvreurii P.H. Hoekstra, sp. nov., Monanthotaxis latistamina P.H. Hoekstra, sp. nov., Monanthotaxis tripetala P.H. Hoekstra, sp. nov. and Monanthotaxis zenkeri P.H. Hoekstra, sp. nov.), one new species from Tanzania (Monanthotaxis filipes P.H. Hoekstra, sp. nov.), one new species from the area around Maputo (Monanthotaxis maputensis P.H. Hoekstra, sp. nov.), one new species from the Comoro Islands (Monanthotaxis komorensis P.H. Hoekstra, sp. nov.) and Monanthotaxis klainei (Engl.) Verdc. var. angustifolia (Boutique) Verdc. is raised to species level leading to the replacement name Monanthotaxis atopostema P.H. Hoekstra, nom. nov. (not Monanthotaxis angustifolia (Exell) Verdc.). Complete descriptions, comparisons with related species, ecological information and IUCN conservation assessments are given for the new species. Five species were classified as critical endangered, two species as endangered, one as vulnerable and one as least concern, warranting the need of further collecting and studying those species

CLAVATA3 is a specific regulator of shoot and floral meristem development affecting the same processes as CLAVATA1

We have previously described the phenotype of Arabidopsis thaliana plants with mutations at the CLAVATA1 (CLV1) locus (Clark, S. E., Running, M. P. and Meyerowitz, E. M. (1993) Development 119, 397-418). Our investigations demonstrated that clv1 plants develop enlarged vegetative and inflorescence apical meristems, and enlarged and indeterminate floral meristems. Here, we present an analysis of mutations at a separate locus, CLAVATA3(CLV3), that disrupt meristem development in a manner similar to clv1mutations. clv3 plants develop enlarged apical meristems as early as the mature embryo stage. clv3 floral meristems are also enlarged compared with wild type, and maintain a proliferating meristem throughout flower development. clv3 root meristems are unaffected, indicating that CLV3 is a specific regulator of shoot and floral meristem development. We demonstrate that the strong clv3-2 mutant is largely epistatic to clv1 mutants, and that the semi-dominance of clv1 alleles is enhanced by double heterozygosity with clv3 alleles, suggesting that these genes work in the same pathway to control meristem development. We propose that CLV1 and CLV3 are required to promote the differentiation of cells at the shoot and floral meristem

Iran supports a great share of biodiversity and floristic endemism for Fritillaria spp. (Liliaceae): A review.

Iran supports a great share of exotic and/or endemic plant genera and species. The genus Fritillaria (Liliaceae) is a precious part of this botanical richness with 19 species, of which 10 are endemic to the country. However, signs are mounting that the country is truly at a crossroads when it comes to preservation of this national wealth. In this regard, an effective conservation strategy should thoroughly consider the classification of Fritillaria, as conservation practices are compromised by knowledge gaps in systematics and taxonomy. As published studies on Fritillaria in Iran have been sporadic and limited in scope, the aim of this review is to provide information necessary to help bridge these information gaps. Our objective is to facilitate increased understanding of the geographic, taxonomic, cytogenetic and phylogenetic status of Iranian Fritillaria, which is vital to meeting the goal of sustainable conservation of the genus in Iran and neighboring areas

Floral development and floral phyllotaxis in Anaxagorea (Annonaceae)

Background and Aims Anaxagorea is the phylogenetically basalmost genus in the large tropical Annonaceae (custard apple family) of Magnoliales, but its floral structure is unknown in many respects. The aim of this study is to analyse evolutionarily interesting floral features in comparison with other genera of the Annonaceae and the sister family Eupomatiaceae. Methods Live flowers of Anaxagorea crassipetala were examined in the field with vital staining, liquid-fixed material was studied with scanning electron microscopy, and microtome section series were studied with light microscopy. In addition, herbarium material of two other Anaxagorea species was cursorily studied with the dissecting microscope. Key Results Floral phyllotaxis in Anaxagorea is regularly whorled (with complex whorls) as in all other Annonaceae with a low or medium number of floral organs studied so far (in those with numerous stamens and carpels, phyllotaxis becoming irregular in the androecium and gynoecium). The carpels are completely plicate as in almost all other Annonaceae. In these features Anaxagorea differs sharply from the sister family Eupomatiaceae, which has spiral floral phyllotaxis and ascidiate carpels. Flat stamens and the presence of inner staminodes differ from most other Annonaceae and may be plesiomorphic in Anaxagorea. However, the inner staminodes appear to be non-secretory in most Anaxagorea species, which differs from inner staminodes in other families of Magnoliales (Eupomatiaceae, Degeneriacae, Himantandraceae), which are secretory. Conclusions Floral phyllotaxis in Anaxagorea shows that there is no signature of a basal spiral pattern in Annonaceae and that complex whorls are an apomorphy not just for a part of the family but for the family in its entirety, and irregular phyllotaxis is derived. This and the presence of completely plicate carpels in Anaxagorea makes the family homogeneous and distinguishes it from the closest relatives in Magnoliale

Floral Development and Systematics of the Caesalpinieae (Leguminosae: Caesalpinioideae).

The floral development of representatives from some of the informal taxonomic groups of the Caesalpinieae was examined. The floral developmental data was then used in a phylogenetic analysis in combination with more traditional morphological characters, including floral, vegetative and fruit characters. The analysis of 53 taxa and 84 characters produced 1215 equally parsimonious trees of length 386 (CI =.317, RI =.585, RCI =.186). Based on this analysis Caesalpinia sensu lato is not monophyletic, since at least two of the other genera in the Caesalpinia group are nested within Caesalpinia sensu lato. Of the infrageneric groups within Caesalpinia sensu lato, the infrageneric groups Libidibia and Brasilettia, and Caesalpinia subgenus Mezoneuron are monophyletic, but the infrageneric groups Caesalpinia sensu stricto, Poincianella, and Russellodendron are not monophyletic. Although many new characters were used in the phylogenetic analysis of the Caesalpinieae, no characters were found which specifically unite the members of the Caesalpinieae. Based on this analysis, the Caesalpinieae is comprised of several disparate lineages and is not a natural group. Two of the informal taxonomic groups of the Caesalpinieae, the Caesalpinia and Peltophorum groups, are not monophyletic based on this analysis. One member of the Peltophorum group, Campsiandra comosa, is more closely related to the Gleditsia and Poeppigia groups than to the rest of the Peltophorum group. The other members of the Peltophorum group included in this analysis are nested within the Caesalpinia group. The Caesalpinia/Peltophorum clade (excluding Campsiandra comosa) is derived within the Leguminosae and is the sister group to the Cassiinae (Cassia, Senna, and Chamaecrista). Together these two clades are sister to a Detarieae/Papilionoideae clade. The Gleditsia group, Poeppigia group and Campsiandra comosa from the Peltophorum group are in a clade with Ceratonia siliqua (Cassieae). Information on floral development was successfully used, along with more traditional morphological characters, in a phylogenetic analysis of the Legominosae

Triandra pellabergensis (Hyacinthaceae subfam. Urgineoideae), a new genus and species from Pella se Berge, Northern Cape Province, South Africa

Within the framework of a taxonomic revision of subfamily Urgineoideae based on morphological, genetic and phytogeographic data covering numerous samples from its whole range of distribution, we here describe a new genus and species from Pella se Berge in northwestern South Africa. Triandra gen. nov. is easily characterized by the absence of stamens associated with the outer tepal whorl, therefore having only three stamens per flower, a character previously unknown in Hyacinthaceae. Triandra pellabergensis sp. nov. produces hypogeal bulbs with filiform proteranthous leaves, spurred bracts, lax racemes with few, nodding, nocturnal flowers and erect capsules with the withered tepals persisting atop. The new species resembles Urginea revoluta in general morphology, although this latter species has six stamens per flower, a different seed morphology, a distinct phytogeographic pattern, and a distant phylogenetic relationship. A complete morphological description is presented for the new genus and species, including data on its biology, ecology and distribution.This work was partly supported by H2020 Research and Innovation Staff Exchange Programme of the European Commission, project 645636: ‘Insect-plant relationships: insights into biodiversity and new applications’ (FlyHigh), and the grants ACIE18–03 UAUSTI18–02 and UAUSTI19-08 from the University of Alicante

Floral Ontogeny and Phylogeny in Malvaceae.

Floral ontogeny in representatives of Malvaceae was compared using scanning electron microscopy. Many aspects of floral development have been resolved by this research, including the presence of a petal-stamen ring meristem in malvaceous taxa. There are several ontogenetic pathways to the formation of this ring meristem; in addition, common petal-stamen mounds are usually present during some stage of development. Stamen proliferation is achieved by partitioning of the ring meristem and furcation of common stamen primordia. Time of initiation overlaps between the corolla and the androecium, and between the androecium and the gynoecium. Helical initiation occurs in the outer organ whorl or whorls and simultaneous initiation occurs in the inner organ whorls or the sets of organs composing these whorls. Ring meristems are sometimes present in bractlet, sepal, and carpel whorls. This research details the complex development leading to the multistaminate androecial columns and the development of the syncarpous gynoecia. Several unusual features are elucidated such as common bractlet primordia, displacement of bractlets, and suppression of organs. Features that distinguish bractlets, from floral bracts and from sepals are discussed. The idea that bifurcation and partitioning events are the likely causes of the bisporangiate condition is refuted. Although the exact mechanism behind the formation of sterile teeth was not ascertained, several factors are identified as sometimes contributing, and some are ruled out as causal. In addition, examination of selected taxa in the sister families Bombacaceae and Sterculiaceae reveals the development of other floral structures such as androgynophores, more than one stamen whorl in the androecium, apocarpous gynoecia, and multistamen meristematic pads. The ontogenetic data has been used to characterize the tribes and distinguish among certain genera in Malvaceae as well as to delineate the family. A cladistic analysis utilizing ontogenetic floral data and morphological data shows that Malvavisceae, Gossypieae, and Malveae are monophyletic, but Hibisceae is paraphyletic. Several evolutionary trends in character traits are revealed and some clarification is provided about phylogenetic relationships within the Malvaceae

Systematics and Floral Evolution in the Plant Genus Garcinia (Clusiaceae)

The pantropical genus Garcinia (Clusiaceae), a group comprised of more than 250 species of dioecious, trees and shrubs, is a common component of lowland tropical forests and is best known by the highly prized fruit of mangosteen (G. mangostana). The genus exhibits as extreme diversity of floral form as is found anywhere in angiosperms and there are many unresolved taxonomic issues surrounding the genus. To understand patterns of floral evolution within the group and to evaluate morphology-based classification schemes involving Garcinia and its relatives, relationships among a broad sample of Garcinia and close relatives were inferred by conducting Bayesian, parsimony, and likelihood analyses of sequence data from two nuclear genes, granule-bound starch synthase (GBSSI) and the internal transcribed spacer (ITS). The phylogenies suggest that all species of Garcinia fall into two major lineages one of which is characterized by the occurrence of nectariferous floral structures of uncertain derivation such as antesepalous appendages and intrastaminal disks and rings and the other by their absence. Several additional clades are supported each sharing particular combinations of floral characters and that generally correspond to sections recognized in the most recent taxonomic treatment of the genus. These results support a broad circumscription of Garcinia to include the segregate genera Ochrocarpos, Pentaphalangium, Rheedia, and Tripetalum. The monophyly of tribe Garcinieae is supported. The nectariferous floral appendages, disks and rings that characterize one of the major lineages identified in the molecular phylogenetic analyses have been hypothesized to represent an outer whorl of stamens. The position of these structures in mature Garcinia flowers does not support this interpretation. To better understand the nature of these structures in Garcinia, floral development and anatomy were studied in a sample of six Garcinia species. An outer whorl, staminodal origin for the disks and appendages is not supported by developmental timing or position. Disks and appendages are not apparent until late in development and the disks arise in the center of flower. Anatomical data are equivocal. These data also reject a gynoecial origin for these structures, and suggest that they are instead intrastaminal receptacular nectaries that are independent of the floral organs