Unveiling foliar secreting sites and secretion composition in the legume tree Swartzia flaemingii Raddi.

Secretory structures in plants play a crucial role in producing bioactive compounds. Despite the potential of the Swartzia genus, comprehensive studies in this context are still scarce. Swartzia is a legume tree (Fabaceae) that occurs in the Brazilian Atlantic Forest, a biodiversity hotspot, and includes species such as Swartzia flaemingii. Therefore, we aim to achieve: (1) identify and characterize the key secretory sites responsible for saponin production in S. flaemingii leaflets; (2) confirm the presence of saponins in S. flaemingii leaves by comparing them with known chemical profiles of other Swartzia species; (3) assess the potential hemolytic and cytotoxic effects of crude leaf extracts. Our investigation unveils the presence of phenolic idioblasts, mucilage cells, and articulate laticifers, which play pivotal roles in defense and adaptation. Notably, we report the first-ever ultrastructural details of laticifers in a legume species. Additionally, oleanane-type saponins were identified in the leaves, giving insights into the chemotaxonomic profile of Swartzia. The crude extracts show low cytotoxicity levels, showcasing as a promising alternative source of saponins. This investigation reinforces the importance of conserving plants in threatened regions like the Atlantic Forest, a global biodiversity hotspot facing substantial anthropogenic pressures.

Corrigendum: Laticifer growth pattern is guided by cytoskeleton organization.

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

Flower structure, anatomy, and sexuality of Chrysophyllum gonocarpum (Sapotaceae).

The Sapotaceae are a significant component of the humid forests of the Neotropics and have many species of economic interest. Chrysophyllum gonocarpum is one of them and its edible fruits have currently acquired a high commercial value. Since there are no studies that cover its floral anatomy and elucidate its sexual system, the objective of the present study is to describe these aspects based on field observations and a detailed anatomical analysis of their flowers. Conventional techniques of plant anatomy are implemented. The results indicate that the species presents cryptic dioecy, showing specimens with morphologically and functionally pistillate flowers (with reduced staminodes), and trees with morphologically hermaphrodite and functionally staminate flowers. In addition, data on floral nectaries and laticiferous are provided.

Protective Effect of Plumeria Pudica Latex Proteins on Intestinal Mucositis Induced by 5-Fluorouracil.

Intestinal mucositis is characterized by inflammation and ulceration of the mucosa that affects the gastrointestinal tract and is associated with administering some drugs, such as 5- Fluorouracil (5-FU), conventional chemotherapy used in clinics for cancer therapy. Inside intestinal mucosa, the 5-FU acts, leading to oxidative stress, stimulating the production/release of proinflammatory cytokines, local accumulation of neutrophils and consequent tissue damage. These alterations favor bacterial proliferation, triggering secondary infections, and are responsible for undesired effects such as myelosuppression and diarrhea. These factors negatively impact oncological patients' quality of life and explain why they commonly interrupt their treatment prematurely. Currently, there is no specific drug with the ability to completely avoid this condition, so the search for new molecules with pharmacological properties that can be used for preventing or ameliorating intestinal mucositis is important. Plumeria pudica is a plant that produces latexcontaining molecules with therapeutic potential. A protein fraction obtained from this latex (LPPp), which comprises a well-defined mixture of chitinases, proteinases proteinase inhibitors, was demonstrated to have antioxidant and anti-inflammatory activities, preserving tissue glutathione and malondialdehyde concentration, reducing superoxide dismutase and myeloperoxidase activity, and reducing the level of proinflammatory cytokines in different experimental models. Given this scenario, inflammation and oxidative stress are directly involved in the pathogenesis of intestinal mucositis promoted by 5-FU. So, the hypothesis is that LPPp could inhibit these factors to attenuate the cytotoxicity of this pathology associated with 5-FU-treatment. This article brings new insights into the potential of the laticifer proteins extracted from the latex of P. pudica and opens new perspectives for the treatment of this type of intestinal mucositis with LPPp.

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.

Insights on the inhibition properties of Jatromollistatin (a cyclic heptapeptide) against Crotalus adamanteus metalloendopeptidase using molecular docking analysis.

Jatropha mollissima is endemic to Brazil and is used for traditional medicinal purposes, including the treatment of snakebite. In this study, latex obtained from this plant was fractioned using reversed-phase chromatography, and the fractions were then screened for peptides. A 755 g/mol peptide was obtained, and MS/MS analyses indicated it had a cyclic sequence (Pro-Leu-Gly-Val-Leu-Leu-Tyr). This peptide sequence was present in the Jatropha genome database, and an identity value of 90.71%, an E-value of 0.0, and a score of 883 with NO-associated protein 1/chloroplastic/mitochondria of Jatropha curcas were obtained from the NCBI nonredundant protein sequence (nr) database. Molecular docking analyses performed with the peptide against a metalloendopeptidase belonging to Crotalus adamanteus snake venom suggested the cyclic peptide establishes favorable interactions with the catalytic site of the enzyme. Therefore, it could inhibit enzyme catalysis. This belief was corroborated by the formation of 6 hydrogen bonds with the linear form of the peptide. Tighter complexation of the cyclic form (41 kcal/mol more energetic) revealed better spatial blocking. The linear form outperformed the cyclic form in complexing the required energy, recruiting more catalytic residues (6/2), and in establishing more hydrogen bonds (6/3). However, cyclic folding provided a more significant spatial block within the catalytic site. The set of results suggests that the cycle peptide, here called Jatromollistatin, which was previously described as jatrophidin and pohlianin A in two other species of Jatropha, is a promising candidate to inhibit venom proteases. This belief is corroborated by the topical use of the latex for initial treatment of snakebites.

Morfo-anatomía foliar de Araujia odorata (Apocynaceae-Asclepiadoideae) en un gradiente altitudinal: histoquímica de laticíferos / Foliar morpho-anatomy of Araujia odorata (Apocynaceae-Asclepiadoideae) in an altitudinal gradient: histochemistry of laticifers

Araujia odorata is a sub-shrub native from Argentina, Brazil, Paraguay and Uruguay, whose latex, roots and leaves are used in traditional medicine. The objective of this work is to study the foliar morpho-anatomy of six populations in an altitudinal gradient (359-2155 m.a.s.l.) of Northwestern Argentine and to determine the nature of the compounds present in the laticiferous of the stems and fruits using conventional techniques for plant anatomy. The populations under study did not show significant morpho-anatomical differences. They presented simple leaves, pinnated brochydodromous venation, amphiestomatic isolateral lamina, brachy, anomo and amphicyclocytic stomata, eglandular trichomes, midvein with bicolateral vascular bundle and non-articulated laticifers continuous in the petiole, stem and fruits. Differences in the quantified foliar parameters are observed, however, only the density of trichomes, stomata and the thickness of the cuticle are positively correlated with the altitudinal gradient, indicating phenotypic plasticity. Histochemical analysis of laticifers and other stem idioblasts of A. odoratawas performed for the first time.

Araujia odorata, es un subarbusto nativo de Argentina, Brasil, Paraguay y Uruguay, cuyo látex, raíces y hojas son utilizados en medicina popular. Se plantea como objetivo realizar un estudio morfo-anatómico foliar de seis poblaciones del Noroeste Argentino en un gradiente altitudinal (359-2155 m.s.n.m) y determinar la naturaleza de los compuestos presentes en laticíferos de tallos y frutos mediante técnicas convencionales de anatomía vegetal. Las poblaciones estudiadas no evidenciaron diferencias morfo-anatómicas significativas. Presentan hojas simples, venación pinnada broquidódroma, lámina isolateral anfiestomática, estomas braqui, anomo y anficiclocíticos, tricomas eglandulares, nervio medio con haz bicolateral y laticíferos no-articulados continuos en pecíolo, tallo y frutos. Se observan diferencias en los parámetros foliares cuantificados, sin embargo, solo la de densidad de tricomas, estomas y el espesor de cutícula se correlacionan positivamente con el gradiente altitudinal indicando plasticidad fenotípica. Se realiza por primera vez un análisis histoquímico de los laticíferos y otros idioblastos del tallo A. odorata.

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

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

Bloodwood: the composition and secreting-site of the characteristic red exudate that gives the name to the Swartzia species (Fabaceae).

The Swartzia species are commonly known as bloodwood due to the red exudate released from the stem after injury. This exudate has aroused great interest, and an integrative study is essential to describe it in detail. Thus, this work aimed to identify the red exudate's secreting-site in S. flaemingii and S. langsdorffii, and determine if it is a latex or a resin. Samples of the stem bark and the secondary xylem were prepared for histological analysis. Fresh exudates were dissolved in deuterated methanol and analyzed by 1H-NMR; other samples were resuspended in MeOH:H2O (9:1), partitioned with organic solvents and analyzed by direct infusion mass spectrometry. Total phenolic and total flavonoid contents were determined spectrophotometrically, and antioxidant capacity was determined using ferric reducing antioxidant power assay. The results showed that the exudate is a red latex produced by articulated laticifers located among the phloem cells. The latex is composed of sucrose, catechin glucosides, chlorophyll derivatives, and hederagenin-type saponins. Both samples of S. flaemingii and S. langsdorffii presented high amounts of phenolics and flavonoids, as well as a strong antioxidant capacity. The anatomical study showed that the secreting-site of the Swartzia red exudates were laticifers. This finding allows us to exclude other substances such as resin or oleoresin, generally produced by secretory cavities or ducts. Furthermore, since laticifers are rare in Fabaceae, this finding is significant, and represents an essential taxonomic feature. The showy red color is due to the large amounts of flavonoids. This latex probably has a protective role against microorganisms and photodamage. The bioactive potential of this exudate inspires further studies, which may boost the economic importance of Swartzia.

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.

Cytological differentiation and cell wall involvement in the growth mechanisms of articulated laticifers in Tabernaemontana catharinensis A.DC. (Apocynaceae).

The cellular mechanisms of laticifer growth are of particular interest in plant biology but are commonly neglected. Using transmission electron microscopy and immunocytochemical methods, we recorded cytological differentiation and evaluated the cell wall involvement in the growth of articulated laticifers with intrusive growth in the mature embryo and plant shoot apex of Tabernaemontana catharinensis. The incorporation of adjacent meristematic cells into the laticifer system occurred in the embryo and plant shoot apex, and the incorporated cells acquired features of laticifer, confirming the laticifers' action-inducing mechanism. In the embryo, this was the main growth mechanism, and began with enlargement of the plasmodesmata and the formation of pores between laticifers and meristematic cells. In the plant shoot apex, it began with loose and disassembled walls and the reorientation of the cortical microtubules of the incorporated cell. Plasmodesmata were absent in these laticifers. There was stronger evidence of intrusive growth in undifferentiated portions of the plant shoot apex than in the embryo. The numerous plasmodesmata in laticifers of the embryo may have been related to the lower frequency of intrusive growth. Intrusive growth was associated with presence of arabinan (increasing wall flexibility and fluidity), and absence of galactan (avoiding wall stiffness), and callose (as a consequence of reduction in symplastic connections) in the laticifer walls. The abundance of low de-methyl-esterified homogalacturonan in the middle lamella and corners may reestablish cell-cell bonding in the laticifers. The cell wall features differed between embryo and plant shoot apex and are directly associated to laticifer growth mechanisms.

Foliar secretory structures in Crotoneae (Euphorbiaceae): Diversity, anatomy, and evolutionary significance.

PREMISE OF THE STUDY: Phylogenetic and morphological studies have helped clarify the systematics of large and complex groups such as the tribe Crotoneae (Euphorbiaceae). However, very little is known about the diversity, structure, and function of anatomical features in this tribe. Crotoneae comprises the species-rich pantropical genus Croton and six small neotropical genera. Here we characterized the anatomy of leaf secretory structures in members of this tribe and explored their function and evolutionary significance. METHODS: Young and mature leaves of 26 species were studied using standard anatomical light microscopy techniques. Three sections of Croton and one representative of Brasiliocroton and Astraea were sampled. KEY RESULTS: We identified five types of secretory structures: laticifers, colleters, extrafloral nectaries, idioblasts, and secretory trichomes. Laticifers were present in all species studied except Croton alabamensis, which instead presented secretory parenchyma cells. Articulated laticifers are reported in Crotoneae for the first time. Colleters of the standard type were observed in the majority of the sampled taxa. Extrafloral nectaries were present in section Cleodora and in B. mamoninha, but absent in section Lamprocroton and Astraea lobata. Idioblasts were spread throughout the palisade and/or spongy parenchyma in most of the studied species. Secretory trichomes were restricted to Lamprocroton except for C. imbricatus. CONCLUSIONS: This study revealed a high diversity of secretory structures, including novel ones, in one of the largest clades of Euphorbiaceae. Our results are promising for investigations on the anatomical and ecophysiological bases of species diversification within Euphorbiaceae.

HbNIN2, a cytosolic alkaline/neutral-invertase, is responsible for sucrose catabolism in rubber-producing laticifers of Hevea brasiliensis (para rubber tree).

In Hevea brasiliensis, an alkaline/neutral invertase (A/N-Inv) is responsible for sucrose catabolism in latex (essentially the cytoplasm of rubber-producing laticifers, the source of natural rubber) and implicated in rubber yield. However, neither the gene encoding this enzyme nor its molecular and biochemical properties have been well documented. Three Hevea A/N-Inv genes, namely HbNIN1, 2 and 3, were first cloned and characterized in planta and in Escherichia coli. Cellular localizations of HbNIN2 mRNA and protein were probed. From latex, active A/N-Inv proteins were purified, identified, and explored for enzymatic properties. HbNIN2 was identified as the major A/N-Inv gene functioning in latex based on its functionality in E. coli, its latex-predominant expression, the conspicuous localization of its mRNA and protein in the laticifers, and its expressional correlation with rubber yield. An active A/N-Inv protein was partially purified from latex, and determined as HbNIN2. The enhancement of HbNIN2 enzymatic activity by pyridoxal is peculiar to A/N-Invs in other plants. We conclude that HbNIN2, a cytosolic A/N-Inv, is responsible for sucrose catabolism in rubber laticifers. The results contribute to the studies of sucrose catabolism in plants as a whole and natural rubber synthesis in particular.

Morpho-anatomical analysis of Aspidosperma olivaceum and A. polyneuron, Apocynaceae

The family Apocynaceae includes many medicinal species, such as Aspidosperma olivaceum Müll. Arg. and A. polyneuron Müll. Arg. The first, popularly known as "peroba-branca", is a source of indole alkaloids that are recognized for their antitumor activity. The second, known as "peroba-rosa", is used by some people for treating malaria. To contribute to the knowledge about Brazilian medicinal plants and potential vegetal drugs, a morpho-anatomical analysis of the leaves and stems of these tree species was carried out. The botanical material was fixed, sectioned and stained using standard techniques. Histochemical tests were performed and the material was also analyzed using a scanning electron microscope. Aspidosperma olivaceum and A. polyneuron are morphologically similar, both presenting alternate, simple, elliptic-lanceolate leaves. The leaves are hypostomatic with anomocytic stomata and have non-glandular trichomes. In the stem, there are peripheral phellogen, lignified fibers and some stone cells in the cortex and pith, as well as numerous gelatinous fibers near the phloem. Prismatic calcium oxalate crystals and laticifers are present in the leaves and stems. Unlike A. olivaceum, A. polyneuron also has cyclocytic stomata, predominantly unicellular non-glandular trichomes and a biconvex midrib with a sharper curve on the adaxial side. In addition, A. olivaceum differs because it has some idioblasts with phenolic content.

Caracteristicas anatômicas da casca e produção de látex em plantas de seringueira não enxertadas / Anatomic bark characteristics and latex production in non-grafted rubber trees

As estruturas envolvidas na produção de látex na seringueira são os laticíferos articulados. O objetivo deste estudo foi descrever aspectos anatômicos da casca em seringueiras não enxertadas com quatro, seis e oito anos, visando à seleção de materiais promissores. O material analisado foi obtido através do corte da casca à altura aproximada de 1,50 m do solo, chegando até o xilema da planta. Os cortes transversais foram preparados de acordo com as técnicas usuais de microtécnica vegetal. Os resultados permitem concluir, que a utilização de caracteres anatômicos (diâmetro das células), da espessura da casca e do diâmetro do caule, visando à seleção dos materiais de pés-francos com idades diferentes, apresentaram uma correlação significativa com a produção de látex.

The structures involved in latex production in rubber trees are articulated laticifers. The objective of this study was to describe anatomical aspects of the bark in four, six and eight year old non-grafted rubber plants, with the view of selecting materials of high yield potential. The analyzed material was obtained from bark cut around 1.50 m from the soil up to the xylem of the plant. The transversal cuts were prepared according to standard plant microtechniques. Based on the results, we can conclude that the use of anatomical characteristics (cell diameter), bark thickness and shoot diameter for selecting material from rootstocks plus non-grafted plants of different ages, showed a significant correlation with latex production.

Caracteristicas anatômicas da casca e produção de látex em plantas de seringueira não enxertadas

The structures involved in latex production in rubber trees are articulated laticifers. The objective of this study was to describe anatomical aspects of the bark in four, six and eight year old non-grafted rubber plants, with the view of selecting materials of high yield potential. The analyzed material was obtained from bark cut around 1.50 m from the soil up to the xylem of the plant. The transversal cuts were prepared according to standard plant microtechniques. Based on the results, we can conclude that the use of anatomical characteristics (cell diameter), bark thickness and shoot diameter for selecting material from rootstocks plus non-grafted plants of different ages, showed a significant correlation with latex production.

As estruturas envolvidas na produção de látex na seringueira são os laticíferos articulados. O objetivo deste estudo foi descrever aspectos anatômicos da casca em seringueiras não enxertadas com quatro, seis e oito anos, visando à seleção de materiais promissores. O material analisado foi obtido através do corte da casca à altura aproximada de 1,50 m do solo, chegando até o xilema da planta. Os cortes transversais foram preparados de acordo com as técnicas usuais de microtécnica vegetal. Os resultados permitem concluir, que a utilização de caracteres anatômicos (diâmetro das células), da espessura da casca e do diâmetro do caule, visando à seleção dos materiais de pés-francos com idades diferentes, apresentaram uma correlação significativa com a produção de látex.

Contribuição ao estudo anatômico do caule de Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson, Apocynaceae / Contribution to the anatomical study of the stem of Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson, Apocynaceae

Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson, Apocynaceae, denominada comumente de sucuuba ou janaguba, é uma espécie arbórea, latescente, da região amazônica, cujo tronco é ereto e a casca rugosa. As atividades antiinflamatória e analgésica e a baixa toxicidade foram estabelecidas em diferentes pesquisas. Com o objetivo de estabelecer caracteres anatômicos aplicáveis à identificação da planta e da droga vegetal, analisou-se o caule em estrutura secundária, que consiste da casca e da região caulinar mais interna. A primeira periderme é observada nas camadas subepidérmicas e o córtex constitui-se de numerosos laticíferos ramificados, idioblastos com cristais de oxalato de cálcio e células parenquimáticas contendo amiloplastos. Uma bainha esclerenquimática descontínua de fibras com paredes espessadas circunda o sistema vascular, cuja organização é bicolateral. As células do parênquima medular apresentam as mesmas características do córtex. Em níveis mais inferiores, a região cortical se reduz e numerosas fibras e células pétreas localizam-se no floema externo.

Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson, Apocynaceae, popularly known as sucuuba and janaguba, is a laticiferous woody species from the Amazonian region. The stem is upright and the bark is rugous. Different investigations have confirmed its anti-inflammatory and analgesic activities as well as low toxicity. Aiming to establish anatomical characters for the plant and drug identification, the stem in secondary growth, consisting of the bark and the most internal region, has been analysed. The first periderm is observed in the sub-epidermal layers and the cortex is composed of several branched laticifers, idioblasts containing calcium oxalate crystals and parenchymatic cells having amiloplasts. A non-continuous sclerenchymatic sheath with thick cell-walled fibres encircles the vascular system, whose organization is bicollateral. The pith cells are similar to the cortex ones. On lower caulinar levels, the cortical region is reduced and numerous fibres and stone cells occur in the external phloem.