Search Results (9)

Since the 19th century, we have had countless debates, sometimes acrimonious, about the nature of the gynoecium. A pivotal question has been whether all angiosperms possess carpels or if some or all angiosperms are acarpellate. We can resolve these debates if we do not define the carpel as a closed megasporophyll but simply as an appendage that encloses the placenta or a single ovule. This redefinition may, however, lead to confusion because often it may not be clear whether the traditional (classical) definition of the carpel or the redefinition is implied. Therefore, a topographic approach is proposed that is compatible with the redefinition. According to this approach, gynoecia comprise one or more gynoecial appendages and placentas or single ovules that may be formed in different positions. Heterotopy refers to these different positions. In the context of evo-devo, which explores evolutionary changes in development, morpho evo-devo delves into spatial shifts of the placentas and ovules leading to heterotopy. Furthermore, it considers shifts in timing (heterochrony) and other processes leading to heteromorphy. Recognizing spatial shifting of the placentas or a single ovule and other evolutionary processes opens up new vistas in the search for the ancestor(s) of angiosperms and their gynoecia. Full article

Background: A feature of higher plants is the modular principle of body organisation. One of these conservative morphological modules that regulate plant growth, histogenesis and organogenesis is meristems—structures that contain pools of stem cells and are generally organised according to a common principle. Basic content: The development of meristems is under the regulation of molecular modules that contain conservative interacting components and modulate the expression of target genes depending on the developmental context. In this review, we focus on two molecular modules that act in different types of meristems. The WOX-CLAVATA module, which includes the peptide ligand, its receptor and the target transcription factor, is responsible for the formation and control of the activity of all meristem types studied, but it has its own peculiarities in different meristems. Another regulatory module is the so-called florigen-activated complex, which is responsible for the phase transition in the shoot vegetative meristem (e.g., from the vegetative shoot apical meristem to the inflorescence meristem). Conclusions: The review considers the composition and functions of these two functional modules in different developmental programmes, as well as their appearance, evolution and use in plant breeding. Full article

Morphological concepts are used in plant evo-devo (evolutionary developmental biology) and other disciplines of plant biology, and therefore plant morphology is relevant to all of these disciplines. Many plant biologists still rely on classical morphology, according to which there are only three mutually exclusive organ categories in vascular plants such as flowering plants: root, stem (caulome), and leaf (phyllome). Continuum morphology recognizes a continuum between these organ categories. Instead of Aristotelian identity and either/or logic, it is based on fuzzy logic, according to which membership in a category is a matter of degree. Hence, an organ in flowering plants may be a root, stem, or leaf to some degree. Homology then also becomes a matter of degree. Process morphology supersedes structure/process dualism. Hence, structures do not have processes, they are processes, which means they are process combinations. These process combinations may change during ontogeny and phylogeny. Although classical morphology on the one hand and continuum and process morphology on the other use different kinds of logic, they can be considered complementary and thus together they present a more inclusive picture of the diversity of plant form than any one of the three alone. However, continuum and process morphology are more comprehensive than classical morphology. Insights gained from continuum and process morphology can inspire research in plant morphology and plant evo-devo, especially MorphoEvoDevo. Full article

The development of unisexual flowers has been described in a large number of taxa, sampling the diversity of floral phenotypes and sexual systems observed in extant angiosperms, in studies focusing on floral ontogeny, on the evo-devo of unisexuality, or on the genetic and chromosomal bases of unisexuality. We review here such developmental studies, aiming at characterizing the diversity of ontogenic pathways leading to functionally unisexual flowers. In addition, we present for the first time and in a two-dimensional morphospace a quantitative description of the developmental rate of the sexual organs in functionally unisexual flowers, in a non-exhaustive sampling of angiosperms with contrasted floral morphologies. Eventually, recommendations are provided to help plant evo-devo researchers and botanists addressing macroevolutionary and ecological issues to more precisely select the taxa, the biological material, or the developmental stages to be investigated. Full article

The tribe Loteae of the family Leguminosae has major centers of diversity in the Mediterranean Region and California. It is used here to illustrate different traditions of taxonomic interpretation of infraspecific variation among researchers in different continents. Recent accounts of European and Mediterranean taxa commonly make an emphasis on recognizing subspecies. In contrast, accounts of North American Loteae recognize all infraspecific taxa as varieties. Harmonization of taxonomic concepts across continents is essential for a more accurate representation of data in global biodiversity databases. It is reasonable to use the rank of subspecies for geographically defined infraspecific units with localized zones of intergradation. Such subspecies may be at least partially compatible across continents and taxonomic groups. In the present paper, we discuss taxa traditionally included in or associated with Acmispon glaber (Vogel) Brouillet (=Syrmatium glabrum Vogel) and demonstrate a need for recognizing three species, of which one has three geographically defined subspecies. Required nomenclatural combinations are proposed. It is proposed that subspecies rather than varieties should be recognized in a number of other species of North American Loteae (and other plant groups). Inland subspecies of Acmispon glaber and A. maritimus offer an opportunity for comparative analysis in an eco-evo-devo framework. Full article

The development of an ideal model plant located at a key phylogenetic node is critically important to advance functional and regulatory studies of key regulatory genes in the evolutionary developmental (evo-devo) biology field. In this study, we selected Chirita pumila in the family Gesneriaceae, a basal group in Lamiales, as a model plant to optimize its genetic transformation system established previously by us through investigating a series of factors and further conduct functional test of the CYC-like floral symmetry gene CpCYC. By transforming a RNAi:CpCYC vector, we successfully achieved the desired phenotypes of upright actinomorphic flowers, which suggest that CpCYC actually determines the establishment of floral zygomorphy and the horizontal orientation of flowers in C. pumila. We also confirmed the activities of CpCYC promoter in dorsal petals, dorsal/lateral staminodes, as well as the pedicel by transferring a CpCYC promoter:GUS vector into C. pumila. Furthermore, we testified the availability of a transient gene expression system using C. pumila mesophyll protoplasts. The improved transformation system together with the inherent biological features would make C. pumila an attractive new model in functional and regulatory studies for a broad range of evo-devo issues. Full article

Plants and animals are both important for studies in evolutionary developmental biology (EvoDevo). Plant morphology as a valuable discipline of EvoDevo is set for a paradigm shift. Process thinking and the continuum approach in plant morphology allow us to perceive and interpret growing plants as combinations of developmental processes rather than as assemblages of structural units (“organs”) such as roots, stems, leaves, and flowers. These dynamic philosophical perspectives were already favored by botanists and philosophers such as Agnes Arber (1879–1960) and Rolf Sattler (*1936). The acceptance of growing plants as dynamic continua inspires EvoDevo scientists such as developmental geneticists and evolutionary biologists to move towards a more holistic understanding of plants in time and space. This review will appeal to many young scientists in the plant development research fields. It covers a wide range of relevant publications from the past to present. Full article

Leaves constitute the main photosynthetic plant organ and even though their importance is not debated, the origin and development of leaves still is. The leaf developmental network has been elucidated for angiosperms, from genes controlling leaf initiation, to leaf polarity and shape. There are four KANADI (KAN) paralogs in Arabidopsis thaliana needed for organ polarity with KAN1 and KAN2 specifying abaxial leaf identity. Yet, studies of this gene lineage outside angiosperms are required to better understand the evolutionary patterns of leaf development and the role of KAN homologs. We studied the evolution of KAN genes across vascular plants and their expression by in situ hybridization in the fern, Equisetum hyemale and the lycophyte Selaginella moellendorffii. Our results show that the expression of KAN genes in leaves is similar between ferns and angiosperms. However, the expression patterns observed in the lycophyte S. moellendorffii are significantly different compared to all other vascular plants, suggesting that the KAN function in leaf polarity is likely only conserved across ferns, gymnosperms, and angiosperms. This study indicates that mechanisms for leaf development are different in lycophytes compared to other vascular plants. Full article

To explain the amazing morphological and biomechanical analogy between two distantly related vertebrates as are a dolphin and a shark, an explanation exclusively framed in terms of adaptation (i.e., in terms of the Darwinian survival of the fittest) is far from satisfactory. The same is true, of course, of any other comparison between structurally similar, but phylogenetically unrelated organisms. A purely evolutionary argument does not throw any light on how the developmental processes of their ancestors could eventually evolve in such a way as to eventually produce these peculiar phenotypes (the arrival of the fittest). How does Nature play with animal and plant form? To address the issue of the evolution of possible forms, we cannot ignore that these are products of development. This invites adopting the integrated perspective, currently known as evolutionary developmental biology, or evo-devo. Paths through the maze of living forms are not satisfactorily explained in terms of pure geometrical transformations or of the adaptive value of the phenotypes eventually produced. The emergence of form is largely dependent on the intrinsic evolvability of the developmental processes that translate the genotype into phenotypes. As a consequence, development makes analogous structures more likely to evolve than a pure adaptationist argument would ever suggest. Full article