Abscission Layer Formation as a Resistance Response of Peruvian Apple Cactus Against Glomerella cingulata

Cereus hildmannianus (K.) Schum. (Cactaceae): Ethnomedical uses, phytochemistry and biological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Cereus hildmannianus (K.) Schum. (syn. C. peruvianus) is a native medicinal plant in the Neotropical region. C. hildmannianus cladodes extracts are used in folk medicine for weight loss, reducing cholesterol, low-density lipoprotein (LDL) levels, as diuretic and cardiotonic, and to treat various diseases, including pulmonary disorders, rheumatism, and in topical treatment for wounds and lithiasis. Fruits and flowers of C. hildmmanianus have high nutritional value.

AIM OF THE REVIEW

In this review, previous reports on C. hildmannianus (syn. C. peruvianus) concerning its botanical description, geographical distribution, ethnomedicinal use, phytochemistry, in vitro and in vivo pharmacological properties, food benefits and plant biotechnology were summarized.

MATERIALS AND METHODS

Scientific search engines, including ScienceDirect, Capes Journals Portal, Google Scholar, PubMed, Scielo, and Scifinder, were consulted to gather data on C. hildmannianus. The present review is an up-to-date and comprehensive analysis of phytochemical compounds, ethnomedicinal uses, phytopharmacological activities, and food value of cladodes, flowers, fruits, seeds, and tissue culture from C. hildmannianus.

RESULTS

In traditional medicine, C.hildmannianus is used to treat various diseases, including pulmonary disorders, rheumatism, and in topical treatment for wounds and lithiasis. The extracts from the cladodes of C. hildmannianus exhibited numerous in vitro and in vivo pharmacological activities such as gastroprotective, antioxidant, antifungal, ovicidal, hemagglutinating and slimming, and anticancer activity. These extracts' substances belong to different classes of chemical compounds such as fatty acids, polysaccharides, terpenes, alkaloids, phenolic acids, and flavonoids CONCLUSIONS: Ethnomedicinal surveys have indicated the use of C. hildmannianus, an important medicinal plant in South America, for the treatment of various diseases. The ethnobotanical, phytochemical, pharmacological, and ethnomedicinal properties from various morphological parts of the plant of C. hildmannianus were highlighted in this review, which provides information for future studies, commercial exploration and reveals that this plant has a huge potential for pharmaceutical and nutraceutical applications.

Defense-Related Responses in Fruit of the Nonhost Chili Pepper against Xanthomonas axonopodis pv. glycines Infection

Xanthomonas axonopodis pv. glycines (Xag ) is a necrotrophic bacterial pathogen of the soybean that causes bacterial pustules and is a nonhost pathogen of the chili pepper. In the current study, chili pepper fruit wound inoculated in planta with Xag 8ra formed necrotic lesions on the fruit surface and induced several structural and chemical barriers systemically in the fruit tissue. The initial defense response included programmed cell death of necrotizing and necrotized cells, which was characterized by nuclear DNA cleavage, as detected by TUNEL-confocal laser scanning microscopy (CLSM), and phosphatidylserine exposure on cell walls distal to the infection site, as detected by Annexin V FLUOS-CLSM. These two responses may facilitate cell killing and enhance transportation of cell wall materials used for cell wall thickening, respectively. The cells beneath the necrotic tissue were enlarged and divided to form periclinal cell walls, resulting in extensive formation of several parallel boundary layers at the later stages of infection, accompanying the deposition of wall fortification materials for strengthening structural defenses. These results suggest that nonhost resistance of chili pepper fruit against the nonhost necrotrophic pathogen Xag 8ra is activated systematically from the initial infection until termination of the infection cycle, resulting in complete inhibition of bacterial pathogenesis by utilizing organ-specific in situ physiological events governed by the expression of genes in the plant fruit organ.

Why do viruses need phloem for systemic invasion of plants?

Plant viruses use sieve elements in phloem as the route of long-distance movement and systemic infection in plants. Plants, in turn, deploy RNA silencing, R-gene mediated defence and other mechanisms to prevent phloem transport of viruses. Cell-to-cell movement of viruses from an initially infected leaf to stem and other parts of the plant could be another possibility for systemic invasion, but it is considered to be too slow. This idea is supported by observations made on viruses that are deficient in phloem loading. The leaf abscission zone forming at the base of the petiole may constitute a barrier that prevents viral cell-to-cell movement. The abscission zone and protective layer are difficult to localize in the petiole until the leaf reaches an advanced stage of senescence. Viruses tagged with the green fluorescent protein are helpful for localization and study of the developing abscission zone.

Structural Modifications and Programmed Cell Death of Chili Pepper Fruit Related to Resistance Responses to Colletotrichum gloeosporioides Infection

ABSTRACT Postharvest (detached) and in planta (attached) fruits of pepper plants, Capsicum annuum cv. Jejujaerae (susceptible) and Capsicum baccatum cv. PBC80 (resistant), inoculated with the anthracnose pathogen Colletotrichum gloeosporioides were examined using light, confocal laser scanning, and electron microscopy to compare the cytological differences between the compatible and incompatible interactions. In nonwound inoculation of postharvest pepper fruit, resistant pepper tissues showed a significant increase in the thickness of the cuticle layer compared with that of the susceptible and noninoculated fruit. Cytological features of programmed cell death (PCD) were observed in the resistant pepper fruit with postharvest inoculation, and these were characterized by positive responses to terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. The oligonucleosomal fragments of DNA were confirmed electrophoretically as DNA laddering. The PCD-positive responses occurred around the inoculation sites early in in planta wound inoculation in the resistant pepper. Nuclear modifications and structural changes of hypersensitivity were also observed in the resistant fruit, including separation of the plasma membrane from the cell wall, dilation of the endoplasmic reticulum, accumulation of electron-dense inclusions in vacuoles, and cytoplasmic vacuolization accompanying fragmentation of the cytoplasm. These structural changes may also implicate PCD-like host responses. In addition, in planta wound inoculation resulted in cell enlargement and cell division during the later stages of infection to form a periderm-like boundary layer around the inoculation site.