Corrigendum: Laticifer growth pattern is guided by cytoskeleton organization.

[This corrects the article DOI: 10.3389/fpls.2022.971235.].

Laticifer growth pattern is guided by cytoskeleton organization.

Laticifers are secretory structures that produce latex, forming a specialized defense system against herbivory. Studies using anatomical approaches to investigate laticifer growth patterns have described their origin; however, their mode of growth, i.e., whether growth is intrusive or diffuse, remains unclear. Studies investigating how cytoskeleton filaments may influence laticifer shape establishment and growth patterns are lacking. In this study, we combined microtubule immunostaining and developmental anatomy to investigate the growth patterns in different types of laticifers. Standard anatomical methods were used to study laticifer development. Microtubules were labelled through immunolocalization of α-tubulin in three types of laticifers from three different plant species: nonanastomosing (Urvillea ulmacea), anastomosing unbranched with partial degradation of terminal cell walls (Ipomoea nil), and anastomosing branched laticifers with early and complete degradation of terminal cell walls (Asclepias curassavica). In both nonanastomosing and anastomosing laticifers, as well as in differentiating meristematic cells, parenchyma cells and idioblasts, microtubules were perpendicularly aligned to the cell growth axis. The analyses of laticifer microtubule orientation revealed an arrangement that corresponds to those cells that grow diffusely within the plant body. Nonanastomosing and anastomosing laticifers, branched or not, have a pattern which indicates diffuse growth. This innovative study on secretory structures represents a major advance in the knowledge of laticifers and their growth mode.

Bouncing back stronger: Diversity, structure, and molecular regulation of gelatinous fiber development.

Gelatinous fibers (G-fibers) are specialized contractile cells found in a diversity of vascular plant tissues, where they provide mechanical support and/or facilitate plant mobility. G-fibers are distinct from typical fibers by the presence of an innermost thickened G-layer, comprised mainly of axially oriented cellulose microfibrils. Despite the disparate developmental origins-tension wood fibers from the vascular cambium or primary phloem fibers from the procambium-G-fiber development, composition, and molecular signatures are remarkably similar; however, important distinctions do exist. Here, we synthesize current knowledge of the phylogenetic diversity, compositional makeup, and the molecular profiles that characterize G-fiber development and highlight open questions for future investigation.

Stinging Trichomes in Apocynaceae and Their Evolution in Angiosperms.

Stinging trichomes are rare in plants, occurring only in angiosperms, where they are reported for a few genera belonging to six families. Although there is no report of stinging trichomes in Apocynaceae, previous fieldwork collections of Fischeria and Matelea caused us a mild allergic reaction on the skin when we contacted the dense indumentum of the plants. This fact associated with the well-known presence of glandular trichomes with acute apex in both genera raised suspicions that stinging trichomes could be present in the family. Hence, this study aimed to investigate the likely occurrence of stinging trichomes in Fischeria and Matelea. We analyzed vegetative shoots and leaves of Fischeria stellata and Matelea denticulata through the usual procedures of light and scanning electron microscopy. We also performed several histochemical tests to investigate the chemical composition of trichome secretion. We detected that glandular trichomes occur throughout the surface of the leaf and stem. They are multicellular, uniseriate with an apical secretory cell, which has a dilated base and a needle-shaped apex. The secretion is compressed into the acuminate portion of the apical cell by a large vacuole, and crystals are deposited in the cell wall in a subapical position, providing a preferential site of rupture. The secretion, composed of amino acids and/or proteins, is released under mechanical action, causing skin irritation. Based on our detailed morphological and anatomical analyses, and in the functional aspects observed, we concluded that the glandular trichomes in Fischeria and Matelea can indeed be classified as stinging. Thus, Apocynaceae is the seventh family for which this type of trichome has been reported. We also compiled information on stinging trichomes in all families of angiosperms. Their phylogenetic distribution indicates that they have evolved at least 12 times during angiosperm evolution and may represent an evolutionary convergence of plant defense against herbivory.

Corrigendum: Laticifers in Sapindaceae: Structure, Evolution and Phylogenetic Importance.

[This corrects the article DOI: 10.3389/fpls.2020.612985.].

Reaching the top through a tortuous path: helical growth in climbing plants.

Climbing plants have voluble organs, for example, tendrils and modified stems, which twine up neighboring plants to reach the canopy. These organs perform exaggerated circumnutation, during which they grow towards the shaded areas of the forest (skototropism) to find a host. In response to mechanical stimulus, they grow towards the support (thigmotropism), tailoring their development to firmly attach to it (thigmomorphogenesis). The underlying molecular pathways of these crucial mechanisms are virtually unknown. Here, we review current progress on molecular regulation of the development and growth of climber's voluble organs. Recent advances in the subject point epigenetics and sensory biology as the emerging frontiers in the study of climbing plant's growth and functioning. We briefly review new developments on the molecular basis of plants' mechanosensory system, discussing the findings in the context of the climbing habit.

Laticifers in Sapindaceae: Structure, Evolution and Phylogenetic Importance.

Laticifer occurrence and structure are poorly known in Sapindaceae. Occurrence is likely underestimated owing to the low production of latex in most species. We investigated 67 species from 23 genera of Sapindaceae to verify laticifer occurrence and their structural, developmental and chemical features, as well as their evolutionary history in the family. Shoots were collected from herbarium and fresh specimens for histological analyses. Three characters derived from laticifer features were coded and their ancestral states reconstructed through Bayesian stochastic mapping and maximum likelihood estimation. Only articulated non-anastomosing laticifers were found in Sapindaceae. Laticifers differentiate early during shoot development and are found in the cortex, phloem, and pith. Latex is mostly composed of lipids. Callose and suberin were detected in laticifer cell walls in some genera. Reconstruction of laticifer ancestral states showed that laticifers are present in most clades of Sapindaceae with some reversals. Callose in the laticifer cell wall was found exclusively in Serjania and Paullinia (tribe Paullinieae), a character regarded as independently derived. Occurrence of laticifers in Sapindaceae is broader than previously reported. Articulated non-anastomosing laticifers had five independent origins in Sapindaceae with some secondary losses, occurring in five out of six genera of Paullinieae and 10 other genera outside Paullinieae. Particularly, callose in the laticifer cell wall evolved independently twice in the family, and its occurrence may be interpreted as a key-innovation that promoted the diversification of Paullinia and Serjania. Our study suggests that laticifer characters may be useful in understanding the generic relationships within the family.

Toward understanding inflorescence development and architecture in Passiflora: insights from comparative anatomy and expression of APETALA1.

PREMISE: The inflorescence of Passiflora species originates from a bud complex that derives from an initially undivided meristem and ultimately produces flowers and tendrils. Because the development of the inflorescence structures derived from such meristems has been variously interpreted, we investigated the ontogeny of the bud complex and the expression of APETALA1 (AP1) in Passiflora species. METHODS: The anatomical development of 15 species of Passiflora was analyzed using light and scanning electron microscopy. We localized AP1 expression in tissues during inflorescence initiation in two Passiflora species using in situ hybridization. RESULTS: In most species, the first primordium to differentiate from the bud complex is a bract, which develops laterally to what will become the inflorescence first-order axis, in this case, the tendril. The bract axillary meristem originates the second-order inflorescence axis meristem, which produces two bracteoles, subsequently developing into a floral meristem. AP1 is uniformly expressed in the initially undivided meristem, with expression maintained in the organ primordia derived from the bud complex. Signal is particularly strong in tendril tips. CONCLUSIONS: We concluded that what is often understood as the first bract produced by a floral meristem actually is produced by the original axillary meristem. Bracteoles develop from the meristem in the bract axil; bracteoles plus floral meristem constitute the inflorescence second-order axis. Comparison of inflorescence early developmental stages in different subgenera indicates flowers are arranged in a modified cyme, with the tendril representing the inflorescence terminal portion. PasAP1 has a broad expression pattern and may have an important role during inflorescence development.

Convergent Evolution and the Diverse Ontogenetic Origins of Tendrils in Angiosperms.

Climbers are abundant in tropical forests, where they constitute a major functional plant type. The acquisition of the climbing habit in angiosperms constitutes a key innovation. Successful speciation in climbers is correlated with the development of specialized climbing strategies such as tendrils, i.e., filiform organs with the ability to twine around other structures through helical growth. Tendrils are derived from a variety of morphological structures, e.g., stems, leaves, and inflorescences, and are found in various plant families. In fact, tendrils are distributed throughout the angiosperm phylogeny, from magnoliids to asterids II, making these structures a great model to study convergent evolution. In this study, we performed a thorough survey of tendrils within angiosperms, focusing on their origin and development. We identified 17 tendril types and analyzed their distribution through the angiosperm phylogeny. Some interesting patterns emerged. For instance, tendrils derived from reproductive structures are exclusively found in the Core Eudicots, except from one monocot species. Fabales and Asterales are the orders with the highest numbers of tendrilling strategies. Tendrils derived from modified leaflets are particularly common among asterids, occurring in Polemoniaceae, Bignoniaceae, and Asteraceae. Although angiosperms have a large number of tendrilled representatives, little is known about their origin and development. This work points out research gaps that should help guide future research on the biology of tendrilled species. Additional research on climbers is particularly important given their increasing abundance resulting from environmental disturbance in the tropics.

The molecular control of tendril development in angiosperms.

The climbing habit has evolved multiple times during the evolutionary history of angiosperms. Plants evolved various strategies for climbing, such as twining stems, tendrils and hooks. Tendrils are threadlike organs with the ability to twine around other structures through helical growth; they may be derived from a variety of structures, such as branches, leaflets and inflorescences. The genetic capacity to grow as a tendrilled climber existed in some of the earliest land plants; however, the underlying molecular basis of tendril development has been studied in only a few taxa. Here, we summarize what is known about the molecular basis of tendril development in model and candidate model species from key tendrilled families, that is, Fabaceae, Vitaceae, Cucurbitaceae, Passifloraceae and Bignoniaceae. Studies on tendril molecular genetics and development show the molecular basis of tendril formation and ontogenesis is diverse, even when tendrils have the same ontogenetic origin, for example leaflet-derived tendrils in Fabaceae and Bignoniaceae. Interestingly, all tendrils perform helical growth during contact-induced coiling, indicating that such ability is not correlated with their ontogenetic origin or phylogenetic history. Whether the same genetic networks are involved during helical growth in diverse tendrils still remains to be investigated.

The Importance of Biodiversity E-infrastructures for Megadiverse Countries.

Addressing the challenges of biodiversity conservation and sustainable development requires global cooperation, support structures, and new governance models to integrate diverse initiatives and achieve massive, open exchange of data, tools, and technology. The traditional paradigm of sharing scientific knowledge through publications is not sufficient to meet contemporary demands that require not only the results but also data, knowledge, and skills to analyze the data. E-infrastructures are key in facilitating access to data and providing the framework for collaboration. Here we discuss the importance of e-infrastructures of public interest and the lack of long-term funding policies. We present the example of Brazil's speciesLink network, an e-infrastructure that provides free and open access to biodiversity primary data and associated tools. SpeciesLink currently integrates 382 datasets from 135 national institutions and 13 institutions from abroad, openly sharing ~7.4 million records, 94% of which are associated to voucher specimens. Just as important as the data is the network of data providers and users. In 2014, more than 95% of its users were from Brazil, demonstrating the importance of local e-infrastructures in enabling and promoting local use of biodiversity data and knowledge. From the outset, speciesLink has been sustained through project-based funding, normally public grants for 2-4-year periods. In between projects, there are short-term crises in trying to keep the system operational, a fact that has also been observed in global biodiversity portals, as well as in social and physical sciences platforms and even in computing services portals. In the last decade, the open access movement propelled the development of many web platforms for sharing data. Adequate policies unfortunately did not follow the same tempo, and now many initiatives may perish.

Seed coat development in Velloziaceae: primary homology assessment and insights on seed coat evolution.

UNLABELLED: • PREMISE OF THE STUDY: Seed coat characteristics have historically been used to infer taxonomic relationships and are a potential source of characters for phylogenetic reconstruction. In particular, seed coat morphoanatomy has never been studied in detail in Velloziaceae. One character based on seed surface microsculpture has been used in phylogenies, but was excluded from recent studies owing to problems in primary homology. This work aimed to clarify the origin and general composition of seed coat cell layers in Velloziaceae and to propose hypotheses of primary homology among seed characters.• METHODS: Seed coat development of 24 Velloziaceae species, comprising nine genera, and one species of Pandanaceae (outgroup) was studied using standard anatomical methods. Developmental data were interpreted in the light of a recently published phylogeny.• KEY RESULTS: Eight types of seed coat were identified. Whereas the most common type has four distinct cell layers (two-layered tegmen and testa), we encountered much more variation in seed coat composition than previously reported, the analysis of which revealed some potential synapomorphies. For instance, an exotesta with spiral thickenings may be a synapomorphy of Barbacenia.• CONCLUSIONS: Our results showed that the character states previously used in phylogenies are not based on homologous layers and that the same state was misattributed to species exhibiting quite different seed coats. This study is a first step toward a better understanding of seed coat structure evolution in Velloziaceae.