INTRODUÇÃOAs plantas com potencial medicinal têm sido muito utilizadas para o tratamento de doenças no Brasil, sendo, algumas vezes, o único medicamento disponível à população (Fachinetto & Tedesco, Efeito genotóxico e antiproliferativo de Mikania cordifolia (L. For each one, two treatments were prepared in different concentrations: 4g/500mL and 16g/500mL. A positive control consisting of 10% glyphosate in 90% water, which is an herbicide widely used and known for its genotoxic potential, was also prepared. Distilled water was used as negative control. After a 24-hour period, the infusion of the root tips was collected, fixed in ethanol-acetic acid (3:1) for 24 hours and stored in 70% ethanol. Cells were analyzed in all phases of the cell cycle of A. cepa, a total of 2500, for each group of bulbs. The mitotic index (MI) was calculated and statistically analyzed by the c 2 test at 5%. Results showed that, in both populations of M. cordifolia, a reduction of the MI in all treatments compared with the negative control was observed. In both populations, an increase in the mitotic index values was obtained with increasing concentration of the infusion. Chromosomal aberrations were observed in both populations studied. In conclusion, infusions of M. cordifolia possess antiproliferative and mutagenic effects for the concentrations tested on the cell cycle of A. cepa.
Mechanisms to sense and respond to pathogens have evolved in all species. The plant immune pathway is initiated by the activation of transmembrane receptor kinases that trigger phosphorylation relays resulting in cellular reprogramming. BOTRYTIS-INDUCED KINASE 1 (BIK1) is a direct substrate of multiple immune receptors in Arabidopsis thaliana and is a central regulator of plant immunity. Here, we review how BIK1 activity and protein stability are regulated by a dynamic interplay between phosphorylation and ubiquitination.
A role of non‐glandular emergences in avoiding ozone (O3) damages by preventing its entrance into leaf tissues has been suggested in the O3‐tolerant species Croton floribundus (Euphorbiaceae). However, this function against O3 damage has been underestimated due to the covering wax layer, mostly composed of saturated hydrocarbon, which has low O3 reactivity. To evaluate the role of these emergences in conferring tolerance to O3, we mechanically removed the non‐glandular emergences from leaf blades of C. floribundus, submitted the plants to acute O3 fumigation, and assessed morphological and microscopic alterations. Plants with intact leaves treated with O3 showed the same phenotype as control samples but showed microscopic indicators of accelerated senescence. These alterations indicated a whole‐plant response to O3. In contrast, plants whose leaves had got their emergences removed exhibited specific morphological symptoms as well as microscopic O3 damage. We thus conclude that the leaf emergences constitute a barrier for volatile contention, preventing O3 damage to leaf tissues in C. floribundus. When these structures have been removed, defense volatiles are possibly quickly dispersed, makes this species vulnerable to O3. This study highlights the relevance of surface structures for plant resistance to O3 damages, complementing biochemical defenses.
Late leaf rust is a fungal disease in raspberries caused by Aculeastrum americanum (Farl.) M. Scholler U. Braun (syn. Thekopsora americana (Farl.) Aime McTaggart) leading to early defoliation and yield losses. Red raspberries (Rubus idaeus L.) are susceptible to this pathogen, although this susceptibility varies among cultivars. In contrast, black raspberries were previously reported to be more resistant (Rubus occidentalis L.) and immune (Rubus niveus Thunb.) to this pathogen, raising their importance in plant breeding programs. However, what features make them respond differently to the same pathogen? In this study, we characterize for the first time the pre- and post-formed structural and biochemical defense mechanisms of R. idaeus cv. Autumn Bliss, R. occidentalis and R. niveus. Ultrastructural and histopathological analyses were used to uncover the interactions between these raspberries and A. americanum. The ultrastructural results indicate that the pathogen germinates on both leaf surfaces but can only form appressoria on the stomata. Although the three raspberry species were infected and colonized by A. americanum, a clear difference in susceptibility was observed between them. A compact mesophyll, pre- and post-formed phenolic compounds, and post-formed pectic compounds were the main plant defense mechanisms against fungal colonization. These findings provide new information about raspberries’ defense mechanisms in response to A. americanum and elucidate the interactions occurring in these pathosystems.
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